This is the v1 version, had the v2 before.

LICENSE

@@ -1,8 +1,8 @@
 The MIT License (MIT)
 
 Copyright (c) 2013 The Go-IMAP Authors
+Copyright (c) 2016 emersion
 Copyright (c) 2016 Proton Technologies AG
-Copyright (c) 2023 Simon Ser
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -1,29 +1,182 @@
 # go-imap
 
-[![Go Reference](https://pkg.go.dev/badge/github.com/emersion/go-imap/v2.svg)](https://pkg.go.dev/github.com/emersion/go-imap/v2)
+[![godocs.io](https://godocs.io/github.com/emersion/go-imap?status.svg)](https://godocs.io/github.com/emersion/go-imap)
+[![builds.sr.ht status](https://builds.sr.ht/~emersion/go-imap/commits/master.svg)](https://builds.sr.ht/~emersion/go-imap/commits/master?)
 
-An [IMAP4rev2] library for Go.
+An [IMAP4rev1](https://tools.ietf.org/html/rfc3501) library written in Go. It
+can be used to build a client and/or a server.
 
 > **Note**
-> This is the README for go-imap v2. This new major version is still in
-> development. For go-imap v1, see the [v1 branch].
+> This is the README for go-imap v1. go-imap v2 is in development, see the
+> [v2 branch](https://github.com/emersion/go-imap/tree/v2) for more details.
 
 ## Usage
 
-To add go-imap to your project, run:
+### Client [![godocs.io](https://godocs.io/github.com/emersion/go-imap/client?status.svg)](https://godocs.io/github.com/emersion/go-imap/client)
 
-    go get github.com/emersion/go-imap/v2
+```go
+package main
 
-Documentation and examples for the module are available here:
+import (
+	"log"
 
-- [Client docs]
-- [Server docs]
+	"github.com/emersion/go-imap/client"
+	"github.com/emersion/go-imap"
+)
+
+func main() {
+	log.Println("Connecting to server...")
+
+	// Connect to server
+	c, err := client.DialTLS("mail.example.org:993", nil)
+	if err != nil {
+		log.Fatal(err)
+	}
+	log.Println("Connected")
+
+	// Don't forget to logout
+	defer c.Logout()
+
+	// Login
+	if err := c.Login("username", "password"); err != nil {
+		log.Fatal(err)
+	}
+	log.Println("Logged in")
+
+	// List mailboxes
+	mailboxes := make(chan *imap.MailboxInfo, 10)
+	done := make(chan error, 1)
+	go func () {
+		done <- c.List("", "*", mailboxes)
+	}()
+
+	log.Println("Mailboxes:")
+	for m := range mailboxes {
+		log.Println("* " + m.Name)
+	}
+
+	if err := <-done; err != nil {
+		log.Fatal(err)
+	}
+
+	// Select INBOX
+	mbox, err := c.Select("INBOX", false)
+	if err != nil {
+		log.Fatal(err)
+	}
+	log.Println("Flags for INBOX:", mbox.Flags)
+
+	// Get the last 4 messages
+	from := uint32(1)
+	to := mbox.Messages
+	if mbox.Messages > 3 {
+		// We're using unsigned integers here, only subtract if the result is > 0
+		from = mbox.Messages - 3
+	}
+	seqset := new(imap.SeqSet)
+	seqset.AddRange(from, to)
+
+	messages := make(chan *imap.Message, 10)
+	done = make(chan error, 1)
+	go func() {
+		done <- c.Fetch(seqset, []imap.FetchItem{imap.FetchEnvelope}, messages)
+	}()
+
+	log.Println("Last 4 messages:")
+	for msg := range messages {
+		log.Println("* " + msg.Envelope.Subject)
+	}
+
+	if err := <-done; err != nil {
+		log.Fatal(err)
+	}
+
+	log.Println("Done!")
+}
+```
+
+### Server [![godocs.io](https://godocs.io/github.com/emersion/go-imap/server?status.svg)](https://godocs.io/github.com/emersion/go-imap/server)
+
+```go
+package main
+
+import (
+	"log"
+
+	"github.com/emersion/go-imap/server"
+	"github.com/emersion/go-imap/backend/memory"
+)
+
+func main() {
+	// Create a memory backend
+	be := memory.New()
+
+	// Create a new server
+	s := server.New(be)
+	s.Addr = ":1143"
+	// Since we will use this server for testing only, we can allow plain text
+	// authentication over unencrypted connections
+	s.AllowInsecureAuth = true
+
+	log.Println("Starting IMAP server at localhost:1143")
+	if err := s.ListenAndServe(); err != nil {
+		log.Fatal(err)
+	}
+}
+```
+
+You can now use `telnet localhost 1143` to manually connect to the server.
+
+## Extensions
+
+Support for several IMAP extensions is included in go-imap itself. This
+includes:
+
+* [APPENDLIMIT](https://tools.ietf.org/html/rfc7889)
+* [CHILDREN](https://tools.ietf.org/html/rfc3348)
+* [ENABLE](https://tools.ietf.org/html/rfc5161)
+* [IDLE](https://tools.ietf.org/html/rfc2177)
+* [IMPORTANT](https://tools.ietf.org/html/rfc8457)
+* [LITERAL+](https://tools.ietf.org/html/rfc7888)
+* [MOVE](https://tools.ietf.org/html/rfc6851)
+* [SASL-IR](https://tools.ietf.org/html/rfc4959)
+* [SPECIAL-USE](https://tools.ietf.org/html/rfc6154)
+* [UNSELECT](https://tools.ietf.org/html/rfc3691)
+
+Support for other extensions is provided via separate packages. See below.
+
+## Extending go-imap
+
+### Extensions
+
+Commands defined in IMAP extensions are available in other packages. See [the
+wiki](https://github.com/emersion/go-imap/wiki/Using-extensions#using-client-extensions)
+to learn how to use them.
+
+* [COMPRESS](https://github.com/emersion/go-imap-compress)
+* [ID](https://github.com/ProtonMail/go-imap-id)
+* [METADATA](https://github.com/emersion/go-imap-metadata)
+* [NAMESPACE](https://github.com/foxcpp/go-imap-namespace)
+* [QUOTA](https://github.com/emersion/go-imap-quota)
+* [SORT and THREAD](https://github.com/emersion/go-imap-sortthread)
+* [UIDPLUS](https://github.com/emersion/go-imap-uidplus)
+
+### Server backends
+
+* [Memory](https://github.com/emersion/go-imap/tree/master/backend/memory) (for testing)
+* [Multi](https://github.com/emersion/go-imap-multi)
+* [PGP](https://github.com/emersion/go-imap-pgp)
+* [Proxy](https://github.com/emersion/go-imap-proxy)
+* [Notmuch](https://github.com/stbenjam/go-imap-notmuch) - Experimental gateway for [Notmuch](https://notmuchmail.org/)
+
+### Related projects
+
+* [go-message](https://github.com/emersion/go-message) - parsing and formatting MIME and mail messages
+* [go-msgauth](https://github.com/emersion/go-msgauth) - handle DKIM, DMARC and Authentication-Results
+* [go-pgpmail](https://github.com/emersion/go-pgpmail) - decrypting and encrypting mails with OpenPGP
+* [go-sasl](https://github.com/emersion/go-sasl) - sending and receiving SASL authentications
+* [go-smtp](https://github.com/emersion/go-smtp) - building SMTP clients and servers
 
 ## License
 
 MIT
-
-[IMAP4rev2]: https://www.rfc-editor.org/rfc/rfc9051.html
-[v1 branch]: https://github.com/emersion/go-imap/tree/v1
-[Client docs]: https://pkg.go.dev/github.com/emersion/go-imap/v2/imapclient
-[Server docs]: https://pkg.go.dev/github.com/emersion/go-imap/v2/imapserver

backend/appendlimit.go

@@ -0,0 +1,29 @@
+package backend
+
+import (
+	"errors"
+)
+
+// An error that should be returned by User.CreateMessage when the message size
+// is too big.
+var ErrTooBig = errors.New("Message size exceeding limit")
+
+// A backend that supports retrieving per-user message size limits.
+type AppendLimitBackend interface {
+	Backend
+
+	// Get the fixed maximum message size in octets that the backend will accept
+	// when creating a new message. If there is no limit, return nil.
+	CreateMessageLimit() *uint32
+}
+
+// A user that supports retrieving per-user message size limits.
+type AppendLimitUser interface {
+	User
+
+	// Get the fixed maximum message size in octets that the backend will accept
+	// when creating a new message. If there is no limit, return nil.
+	//
+	// This overrides the global backend limit.
+	CreateMessageLimit() *uint32
+}

backend/backend.go

@@ -0,0 +1,20 @@
+// Package backend defines an IMAP server backend interface.
+package backend
+
+import (
+	"errors"
+
+	"github.com/emersion/go-imap"
+)
+
+// ErrInvalidCredentials is returned by Backend.Login when a username or a
+// password is incorrect.
+var ErrInvalidCredentials = errors.New("Invalid credentials")
+
+// Backend is an IMAP server backend. A backend operation always deals with
+// users.
+type Backend interface {
+	// Login authenticates a user. If the username or the password is incorrect,
+	// it returns ErrInvalidCredentials.
+	Login(connInfo *imap.ConnInfo, username, password string) (User, error)
+}

backend/backendutil/backendutil.go

@@ -0,0 +1,2 @@
+// Package backendutil provides utility functions to implement IMAP backends.
+package backendutil

backend/backendutil/backendutil_test.go

@@ -0,0 +1,79 @@
+package backendutil
+
+import (
+	"time"
+)
+
+var testDate, _ = time.Parse(time.RFC1123Z, "Sat, 18 Jun 2016 12:00:00 +0900")
+
+const testHeaderString = "Content-Type: multipart/mixed; boundary=message-boundary\r\n" +
+	"Date: Sat, 18 Jun 2016 12:00:00 +0900\r\n" +
+	"Date: Sat, 19 Jun 2016 12:00:00 +0900\r\n" +
+	"From: Mitsuha Miyamizu <mitsuha.miyamizu@example.org>\r\n" +
+	"Reply-To: Mitsuha Miyamizu <mitsuha.miyamizu+replyto@example.org>\r\n" +
+	"Message-Id: 42@example.org\r\n" +
+	"Subject: Your Name.\r\n" +
+	"To: Taki Tachibana <taki.tachibana@example.org>\r\n" +
+	"\r\n"
+
+const testHeaderFromToString = "From: Mitsuha Miyamizu <mitsuha.miyamizu@example.org>\r\n" +
+	"To: Taki Tachibana <taki.tachibana@example.org>\r\n" +
+	"\r\n"
+
+const testHeaderDateString = "Date: Sat, 18 Jun 2016 12:00:00 +0900\r\n" +
+	"Date: Sat, 19 Jun 2016 12:00:00 +0900\r\n" +
+	"\r\n"
+
+const testHeaderNoFromToString = "Content-Type: multipart/mixed; boundary=message-boundary\r\n" +
+	"Date: Sat, 18 Jun 2016 12:00:00 +0900\r\n" +
+	"Date: Sat, 19 Jun 2016 12:00:00 +0900\r\n" +
+	"Reply-To: Mitsuha Miyamizu <mitsuha.miyamizu+replyto@example.org>\r\n" +
+	"Message-Id: 42@example.org\r\n" +
+	"Subject: Your Name.\r\n" +
+	"\r\n"
+
+const testAltHeaderString = "Content-Type: multipart/alternative; boundary=b2\r\n" +
+	"\r\n"
+
+const testTextHeaderString = "Content-Disposition: inline\r\n" +
+	"Content-Type: text/plain\r\n" +
+	"\r\n"
+
+const testTextContentTypeString = "Content-Type: text/plain\r\n" +
+	"\r\n"
+
+const testTextNoContentTypeString = "Content-Disposition: inline\r\n" +
+	"\r\n"
+
+const testTextBodyString = "What's your name?"
+
+const testTextString = testTextHeaderString + testTextBodyString
+
+const testHTMLHeaderString = "Content-Disposition: inline\r\n" +
+	"Content-Type: text/html\r\n" +
+	"\r\n"
+
+const testHTMLBodyString = "<div>What's <i>your\r\n</i> name?</div>"
+
+const testHTMLString = testHTMLHeaderString + testHTMLBodyString
+
+const testAttachmentHeaderString = "Content-Disposition: attachment; filename=note.txt\r\n" +
+	"Content-Type: text/plain\r\n" +
+	"\r\n"
+
+const testAttachmentBodyString = "My name is Mitsuha."
+
+const testAttachmentString = testAttachmentHeaderString + testAttachmentBodyString
+
+const testBodyString = "--message-boundary\r\n" +
+	testAltHeaderString +
+	"\r\n--b2\r\n" +
+	testTextString +
+	"\r\n--b2\r\n" +
+	testHTMLString +
+	"\r\n--b2--\r\n" +
+	"\r\n--message-boundary\r\n" +
+	testAttachmentString +
+	"\r\n--message-boundary--\r\n"
+
+const testMailString = testHeaderString + testBodyString

backend/backendutil/body.go

@@ -0,0 +1,121 @@
+package backendutil
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"mime"
+	nettextproto "net/textproto"
+	"strings"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-message/textproto"
+)
+
+var errNoSuchPart = errors.New("backendutil: no such message body part")
+
+func multipartReader(header textproto.Header, body io.Reader) *textproto.MultipartReader {
+	contentType := header.Get("Content-Type")
+	if !strings.HasPrefix(strings.ToLower(contentType), "multipart/") {
+		return nil
+	}
+
+	_, params, err := mime.ParseMediaType(contentType)
+	if err != nil {
+		return nil
+	}
+
+	return textproto.NewMultipartReader(body, params["boundary"])
+}
+
+// FetchBodySection extracts a body section from a message.
+func FetchBodySection(header textproto.Header, body io.Reader, section *imap.BodySectionName) (imap.Literal, error) {
+	// First, find the requested part using the provided path
+	for i := 0; i < len(section.Path); i++ {
+		n := section.Path[i]
+
+		mr := multipartReader(header, body)
+		if mr == nil {
+			// First part of non-multipart message refers to the message itself.
+			// See RFC 3501, Page 55.
+			if len(section.Path) == 1 && section.Path[0] == 1 {
+				break
+			}
+			return nil, errNoSuchPart
+		}
+
+		for j := 1; j <= n; j++ {
+			p, err := mr.NextPart()
+			if err == io.EOF {
+				return nil, errNoSuchPart
+			} else if err != nil {
+				return nil, err
+			}
+
+			if j == n {
+				body = p
+				header = p.Header
+
+				break
+			}
+		}
+	}
+
+	// Then, write the requested data to a buffer
+	b := new(bytes.Buffer)
+
+	resHeader := header
+	if section.Fields != nil {
+		// Copy header so we will not change value passed to us.
+		resHeader = header.Copy()
+
+		if section.NotFields {
+			for _, fieldName := range section.Fields {
+				resHeader.Del(fieldName)
+			}
+		} else {
+			fieldsMap := make(map[string]struct{}, len(section.Fields))
+			for _, field := range section.Fields {
+				fieldsMap[nettextproto.CanonicalMIMEHeaderKey(field)] = struct{}{}
+			}
+
+			for field := resHeader.Fields(); field.Next(); {
+				if _, ok := fieldsMap[field.Key()]; !ok {
+					field.Del()
+				}
+			}
+		}
+	}
+
+	// Write the header
+	err := textproto.WriteHeader(b, resHeader)
+	if err != nil {
+		return nil, err
+	}
+
+	switch section.Specifier {
+	case imap.TextSpecifier:
+		// The header hasn't been requested. Discard it.
+		b.Reset()
+	case imap.EntireSpecifier:
+		if len(section.Path) > 0 {
+			// When selecting a specific part by index, IMAP servers
+			// return only the text, not the associated MIME header.
+			b.Reset()
+		}
+	}
+
+	// Write the body, if requested
+	switch section.Specifier {
+	case imap.EntireSpecifier, imap.TextSpecifier:
+		if _, err := io.Copy(b, body); err != nil {
+			return nil, err
+		}
+	}
+
+	var l imap.Literal = b
+	if section.Partial != nil {
+		l = bytes.NewReader(section.ExtractPartial(b.Bytes()))
+	}
+	return l, nil
+}

backend/backendutil/body_test.go

@@ -0,0 +1,196 @@
+package backendutil
+
+import (
+	"bufio"
+	"io/ioutil"
+	"strings"
+	"testing"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-message/textproto"
+)
+
+var bodyTests = []struct {
+	section string
+	body    string
+}{
+	{
+		section: "BODY[]",
+		body:    testMailString,
+	},
+	{
+		section: "BODY[1.1]",
+		body:    testTextBodyString,
+	},
+	{
+		section: "BODY[1.2]",
+		body:    testHTMLBodyString,
+	},
+	{
+		section: "BODY[2]",
+		body:    testAttachmentBodyString,
+	},
+	{
+		section: "BODY[HEADER]",
+		body:    testHeaderString,
+	},
+	{
+		section: "BODY[HEADER.FIELDS (From To)]",
+		body:    testHeaderFromToString,
+	},
+	{
+		section: "BODY[HEADER.FIELDS (FROM to)]",
+		body:    testHeaderFromToString,
+	},
+	{
+		section: "BODY[HEADER.FIELDS.NOT (From To)]",
+		body:    testHeaderNoFromToString,
+	},
+	{
+		section: "BODY[HEADER.FIELDS (Date)]",
+		body:    testHeaderDateString,
+	},
+	{
+		section: "BODY[1.1.HEADER]",
+		body:    testTextHeaderString,
+	},
+	{
+		section: "BODY[1.1.HEADER.FIELDS (Content-Type)]",
+		body:    testTextContentTypeString,
+	},
+	{
+		section: "BODY[1.1.HEADER.FIELDS.NOT (Content-Type)]",
+		body:    testTextNoContentTypeString,
+	},
+	{
+		section: "BODY[2.HEADER]",
+		body:    testAttachmentHeaderString,
+	},
+	{
+		section: "BODY[2.MIME]",
+		body:    testAttachmentHeaderString,
+	},
+	{
+		section: "BODY[TEXT]",
+		body:    testBodyString,
+	},
+	{
+		section: "BODY[1.1.TEXT]",
+		body:    testTextBodyString,
+	},
+	{
+		section: "BODY[2.TEXT]",
+		body:    testAttachmentBodyString,
+	},
+	{
+		section: "BODY[2.1]",
+		body:    "",
+	},
+	{
+		section: "BODY[3]",
+		body:    "",
+	},
+	{
+		section: "BODY[2.TEXT]<0.9>",
+		body:    testAttachmentBodyString[:9],
+	},
+}
+
+func TestFetchBodySection(t *testing.T) {
+	for _, test := range bodyTests {
+		test := test
+		t.Run(test.section, func(t *testing.T) {
+			bufferedBody := bufio.NewReader(strings.NewReader(testMailString))
+
+			header, err := textproto.ReadHeader(bufferedBody)
+			if err != nil {
+				t.Fatal("Expected no error while reading mail, got:", err)
+			}
+
+			section, err := imap.ParseBodySectionName(imap.FetchItem(test.section))
+			if err != nil {
+				t.Fatal("Expected no error while parsing body section name, got:", err)
+			}
+
+			r, err := FetchBodySection(header, bufferedBody, section)
+			if test.body == "" {
+				if err == nil {
+					t.Error("Expected an error while extracting non-existing body section")
+				}
+			} else {
+				if err != nil {
+					t.Fatal("Expected no error while extracting body section, got:", err)
+				}
+
+				b, err := ioutil.ReadAll(r)
+				if err != nil {
+					t.Fatal("Expected no error while reading body section, got:", err)
+				}
+
+				if s := string(b); s != test.body {
+					t.Errorf("Expected body section %q to be \n%s\n but got \n%s", test.section, test.body, s)
+				}
+			}
+		})
+	}
+}
+
+func TestFetchBodySection_NonMultipart(t *testing.T) {
+	// https://tools.ietf.org/html/rfc3501#page-55:
+	//  Every message has at least one part number.  Non-[MIME-IMB]
+	//  messages, and non-multipart [MIME-IMB] messages with no
+	//  encapsulated message, only have a part 1.
+
+	testMsgHdr := "From: Mitsuha Miyamizu <mitsuha.miyamizu@example.org>\r\n" +
+		"To: Taki Tachibana <taki.tachibana@example.org>\r\n" +
+		"Subject: Your Name.\r\n" +
+		"Message-Id: 42@example.org\r\n" +
+		"\r\n"
+	testMsgBody := "That's not multipart message. Thought it should be possible to get this text using BODY[1]."
+	testMsg := testMsgHdr + testMsgBody
+
+	tests := []struct {
+		section string
+		body    string
+	}{
+		{
+			section: "BODY[1.MIME]",
+			body:    testMsgHdr,
+		},
+		{
+			section: "BODY[1]",
+			body:    testMsgBody,
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+		t.Run(test.section, func(t *testing.T) {
+			bufferedBody := bufio.NewReader(strings.NewReader(testMsg))
+
+			header, err := textproto.ReadHeader(bufferedBody)
+			if err != nil {
+				t.Fatal("Expected no error while reading mail, got:", err)
+			}
+
+			section, err := imap.ParseBodySectionName(imap.FetchItem(test.section))
+			if err != nil {
+				t.Fatal("Expected no error while parsing body section name, got:", err)
+			}
+
+			r, err := FetchBodySection(header, bufferedBody, section)
+			if err != nil {
+				t.Fatal("Expected no error while extracting body section, got:", err)
+			}
+
+			b, err := ioutil.ReadAll(r)
+			if err != nil {
+				t.Fatal("Expected no error while reading body section, got:", err)
+			}
+
+			if s := string(b); s != test.body {
+				t.Errorf("Expected body section %q to be \n%s\n but got \n%s", test.section, test.body, s)
+			}
+		})
+	}
+}

backend/backendutil/bodystructure.go

@@ -0,0 +1,117 @@
+package backendutil
+
+import (
+	"bufio"
+	"bytes"
+	"io"
+	"io/ioutil"
+	"mime"
+	"strings"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-message/textproto"
+)
+
+type countReader struct {
+	r          io.Reader
+	bytes      uint32
+	newlines   uint32
+	endsWithLF bool
+}
+
+func (r *countReader) Read(b []byte) (int, error) {
+	n, err := r.r.Read(b)
+	r.bytes += uint32(n)
+	if n != 0 {
+		r.newlines += uint32(bytes.Count(b[:n], []byte{'\n'}))
+		r.endsWithLF = b[n-1] == '\n'
+	}
+	// If the stream does not end with a newline - count missing newline.
+	if err == io.EOF {
+		if !r.endsWithLF {
+			r.newlines++
+		}
+	}
+	return n, err
+}
+
+// FetchBodyStructure computes a message's body structure from its content.
+func FetchBodyStructure(header textproto.Header, body io.Reader, extended bool) (*imap.BodyStructure, error) {
+	bs := new(imap.BodyStructure)
+
+	mediaType, mediaParams, err := mime.ParseMediaType(header.Get("Content-Type"))
+	if err == nil {
+		typeParts := strings.SplitN(mediaType, "/", 2)
+		bs.MIMEType = typeParts[0]
+		if len(typeParts) == 2 {
+			bs.MIMESubType = typeParts[1]
+		}
+		bs.Params = mediaParams
+	} else {
+		bs.MIMEType = "text"
+		bs.MIMESubType = "plain"
+	}
+
+	bs.Id = header.Get("Content-Id")
+	bs.Description = header.Get("Content-Description")
+	bs.Encoding = header.Get("Content-Transfer-Encoding")
+
+	if mr := multipartReader(header, body); mr != nil {
+		var parts []*imap.BodyStructure
+		for {
+			p, err := mr.NextPart()
+			if err == io.EOF {
+				break
+			} else if err != nil {
+				return nil, err
+			}
+
+			pbs, err := FetchBodyStructure(p.Header, p, extended)
+			if err != nil {
+				return nil, err
+			}
+			parts = append(parts, pbs)
+		}
+		bs.Parts = parts
+	} else {
+		countedBody := countReader{r: body}
+		needLines := false
+		if bs.MIMEType == "message" && bs.MIMESubType == "rfc822" {
+			// This will result in double-buffering if body is already a
+			// bufio.Reader (most likely it is). :\
+			bufBody := bufio.NewReader(&countedBody)
+			subMsgHdr, err := textproto.ReadHeader(bufBody)
+			if err != nil {
+				return nil, err
+			}
+			bs.Envelope, err = FetchEnvelope(subMsgHdr)
+			if err != nil {
+				return nil, err
+			}
+			bs.BodyStructure, err = FetchBodyStructure(subMsgHdr, bufBody, extended)
+			if err != nil {
+				return nil, err
+			}
+			needLines = true
+		} else if bs.MIMEType == "text" {
+			needLines = true
+		}
+		if _, err := io.Copy(ioutil.Discard, &countedBody); err != nil {
+			return nil, err
+		}
+		bs.Size = countedBody.bytes
+		if needLines {
+			bs.Lines = countedBody.newlines
+		}
+	}
+
+	if extended {
+		bs.Extended = true
+		bs.Disposition, bs.DispositionParams, _ = mime.ParseMediaType(header.Get("Content-Disposition"))
+
+		// TODO: bs.Language, bs.Location
+		// TODO: bs.MD5
+	}
+
+	return bs, nil
+}

backend/backendutil/bodystructure_test.go

@@ -0,0 +1,76 @@
+package backendutil
+
+import (
+	"bufio"
+	"reflect"
+	"strings"
+	"testing"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-message/textproto"
+)
+
+var testBodyStructure = &imap.BodyStructure{
+	MIMEType:    "multipart",
+	MIMESubType: "mixed",
+	Params:      map[string]string{"boundary": "message-boundary"},
+	Parts: []*imap.BodyStructure{
+		{
+			MIMEType:    "multipart",
+			MIMESubType: "alternative",
+			Params:      map[string]string{"boundary": "b2"},
+			Extended:    true,
+			Parts: []*imap.BodyStructure{
+				{
+					MIMEType:          "text",
+					MIMESubType:       "plain",
+					Params:            map[string]string{},
+					Extended:          true,
+					Disposition:       "inline",
+					DispositionParams: map[string]string{},
+					Lines:             1,
+					Size:              17,
+				},
+				{
+					MIMEType:          "text",
+					MIMESubType:       "html",
+					Params:            map[string]string{},
+					Extended:          true,
+					Disposition:       "inline",
+					DispositionParams: map[string]string{},
+					Lines:             2,
+					Size:              37,
+				},
+			},
+		},
+		{
+			MIMEType:          "text",
+			MIMESubType:       "plain",
+			Params:            map[string]string{},
+			Extended:          true,
+			Disposition:       "attachment",
+			DispositionParams: map[string]string{"filename": "note.txt"},
+			Lines:             1,
+			Size:              19,
+		},
+	},
+	Extended: true,
+}
+
+func TestFetchBodyStructure(t *testing.T) {
+	bufferedBody := bufio.NewReader(strings.NewReader(testMailString))
+
+	header, err := textproto.ReadHeader(bufferedBody)
+	if err != nil {
+		t.Fatal("Expected no error while reading mail, got:", err)
+	}
+
+	bs, err := FetchBodyStructure(header, bufferedBody, true)
+	if err != nil {
+		t.Fatal("Expected no error while fetching body structure, got:", err)
+	}
+
+	if !reflect.DeepEqual(testBodyStructure, bs) {
+		t.Errorf("Expected body structure \n%+v\n but got \n%+v", testBodyStructure, bs)
+	}
+}

backend/backendutil/envelope.go

@@ -0,0 +1,58 @@
+package backendutil
+
+import (
+	"net/mail"
+	"strings"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-message/textproto"
+)
+
+func headerAddressList(value string) ([]*imap.Address, error) {
+	addrs, err := mail.ParseAddressList(value)
+	if err != nil {
+		return []*imap.Address{}, err
+	}
+
+	list := make([]*imap.Address, len(addrs))
+	for i, a := range addrs {
+		parts := strings.SplitN(a.Address, "@", 2)
+		mailbox := parts[0]
+		var hostname string
+		if len(parts) == 2 {
+			hostname = parts[1]
+		}
+
+		list[i] = &imap.Address{
+			PersonalName: a.Name,
+			MailboxName:  mailbox,
+			HostName:     hostname,
+		}
+	}
+
+	return list, err
+}
+
+// FetchEnvelope returns a message's envelope from its header.
+func FetchEnvelope(h textproto.Header) (*imap.Envelope, error) {
+	env := new(imap.Envelope)
+
+	env.Date, _ = mail.ParseDate(h.Get("Date"))
+	env.Subject = h.Get("Subject")
+	env.From, _ = headerAddressList(h.Get("From"))
+	env.Sender, _ = headerAddressList(h.Get("Sender"))
+	if len(env.Sender) == 0 {
+		env.Sender = env.From
+	}
+	env.ReplyTo, _ = headerAddressList(h.Get("Reply-To"))
+	if len(env.ReplyTo) == 0 {
+		env.ReplyTo = env.From
+	}
+	env.To, _ = headerAddressList(h.Get("To"))
+	env.Cc, _ = headerAddressList(h.Get("Cc"))
+	env.Bcc, _ = headerAddressList(h.Get("Bcc"))
+	env.InReplyTo = h.Get("In-Reply-To")
+	env.MessageId = h.Get("Message-Id")
+
+	return env, nil
+}

backend/backendutil/envelope_test.go

@@ -0,0 +1,40 @@
+package backendutil
+
+import (
+	"bufio"
+	"reflect"
+	"strings"
+	"testing"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-message/textproto"
+)
+
+var testEnvelope = &imap.Envelope{
+	Date:      testDate,
+	Subject:   "Your Name.",
+	From:      []*imap.Address{{PersonalName: "Mitsuha Miyamizu", MailboxName: "mitsuha.miyamizu", HostName: "example.org"}},
+	Sender:    []*imap.Address{{PersonalName: "Mitsuha Miyamizu", MailboxName: "mitsuha.miyamizu", HostName: "example.org"}},
+	ReplyTo:   []*imap.Address{{PersonalName: "Mitsuha Miyamizu", MailboxName: "mitsuha.miyamizu+replyto", HostName: "example.org"}},
+	To:        []*imap.Address{{PersonalName: "Taki Tachibana", MailboxName: "taki.tachibana", HostName: "example.org"}},
+	Cc:        []*imap.Address{},
+	Bcc:       []*imap.Address{},
+	InReplyTo: "",
+	MessageId: "42@example.org",
+}
+
+func TestFetchEnvelope(t *testing.T) {
+	hdr, err := textproto.ReadHeader(bufio.NewReader(strings.NewReader(testMailString)))
+	if err != nil {
+		t.Fatal("Expected no error while reading mail, got:", err)
+	}
+
+	env, err := FetchEnvelope(hdr)
+	if err != nil {
+		t.Fatal("Expected no error while fetching envelope, got:", err)
+	}
+
+	if !reflect.DeepEqual(env, testEnvelope) {
+		t.Errorf("Expected envelope \n%+v\n but got \n%+v", testEnvelope, env)
+	}
+}

backend/backendutil/flags.go

@@ -0,0 +1,73 @@
+package backendutil
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// UpdateFlags executes a flag operation on the flag set current.
+func UpdateFlags(current []string, op imap.FlagsOp, flags []string) []string {
+	// Don't modify contents of 'flags' slice.  Only modify 'current'.
+	// See https://github.com/golang/go/wiki/SliceTricks
+
+	// Re-use current's backing store
+	newFlags := current[:0]
+	switch op {
+	case imap.SetFlags:
+		hasRecent := false
+		// keep recent flag
+		for _, flag := range current {
+			if flag == imap.RecentFlag {
+				newFlags = append(newFlags, imap.RecentFlag)
+				hasRecent = true
+				break
+			}
+		}
+		// append new flags
+		for _, flag := range flags {
+			if flag == imap.RecentFlag {
+				// Make sure we don't add the recent flag multiple times.
+				if hasRecent {
+					// Already have the recent flag, skip.
+					continue
+				}
+				hasRecent = true
+			}
+			// append new flag
+			newFlags = append(newFlags, flag)
+		}
+	case imap.AddFlags:
+		// keep current flags
+		newFlags = current
+		// Only add new flag if it isn't already in current list.
+		for _, addFlag := range flags {
+			found := false
+			for _, flag := range current {
+				if addFlag == flag {
+					found = true
+					break
+				}
+			}
+			// new flag not found, add it.
+			if !found {
+				newFlags = append(newFlags, addFlag)
+			}
+		}
+	case imap.RemoveFlags:
+		// Filter current flags
+		for _, flag := range current {
+			remove := false
+			for _, removeFlag := range flags {
+				if removeFlag == flag {
+					remove = true
+				}
+			}
+			if !remove {
+				newFlags = append(newFlags, flag)
+			}
+		}
+	default:
+		// Unknown operation, return current flags unchanged
+		newFlags = current
+	}
+	return newFlags
+}

backend/backendutil/flags_test.go

@@ -0,0 +1,86 @@
+package backendutil
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/emersion/go-imap"
+)
+
+var updateFlagsTests = []struct {
+	op    imap.FlagsOp
+	flags []string
+	res   []string
+}{
+	{
+		op:    imap.AddFlags,
+		flags: []string{"d", "e"},
+		res:   []string{"a", "b", "c", "d", "e"},
+	},
+	{
+		op:    imap.AddFlags,
+		flags: []string{"a", "d", "b"},
+		res:   []string{"a", "b", "c", "d"},
+	},
+	{
+		op:    imap.RemoveFlags,
+		flags: []string{"b", "v", "e", "a"},
+		res:   []string{"c"},
+	},
+	{
+		op:    imap.SetFlags,
+		flags: []string{"a", "d", "e"},
+		res:   []string{"a", "d", "e"},
+	},
+	// Test unknown op for code coverage.
+	{
+		op:    imap.FlagsOp("TestUnknownOp"),
+		flags: []string{"a", "d", "e"},
+		res:   []string{"a", "b", "c"},
+	},
+}
+
+func TestUpdateFlags(t *testing.T) {
+	flagsList := []string{"a", "b", "c"}
+	for _, test := range updateFlagsTests {
+		// Make a backup copy of 'test.flags'
+		origFlags := append(test.flags[:0:0], test.flags...)
+		// Copy flags
+		current := append(flagsList[:0:0], flagsList...)
+		got := UpdateFlags(current, test.op, test.flags)
+
+		if !reflect.DeepEqual(got, test.res) {
+			t.Errorf("Expected result to be \n%v\n but got \n%v", test.res, got)
+		}
+		// Verify that 'test.flags' wasn't modified
+		if !reflect.DeepEqual(origFlags, test.flags) {
+			t.Errorf("Unexpected change to operation flags list changed \nbefore %v\n after \n%v",
+				origFlags, test.flags)
+		}
+	}
+}
+
+func TestUpdateFlags_Recent(t *testing.T) {
+	current := []string{}
+
+	current = UpdateFlags(current, imap.SetFlags, []string{imap.RecentFlag})
+
+	res := []string{imap.RecentFlag}
+	if !reflect.DeepEqual(current, res) {
+		t.Errorf("Expected result to be \n%v\n but got \n%v", res, current)
+	}
+
+	current = UpdateFlags(current, imap.SetFlags, []string{"something"})
+
+	res = []string{imap.RecentFlag, "something"}
+	if !reflect.DeepEqual(current, res) {
+		t.Errorf("Expected result to be \n%v\n but got \n%v", res, current)
+	}
+
+	current = UpdateFlags(current, imap.SetFlags, []string{"another", imap.RecentFlag})
+
+	res = []string{imap.RecentFlag, "another"}
+	if !reflect.DeepEqual(current, res) {
+		t.Errorf("Expected result to be \n%v\n but got \n%v", res, current)
+	}
+}

backend/backendutil/search.go

@@ -0,0 +1,230 @@
+package backendutil
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"strings"
+	"time"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-message"
+	"github.com/emersion/go-message/mail"
+	"github.com/emersion/go-message/textproto"
+)
+
+func matchString(s, substr string) bool {
+	return strings.Contains(strings.ToLower(s), strings.ToLower(substr))
+}
+
+func bufferBody(e *message.Entity) (*bytes.Buffer, error) {
+	b := new(bytes.Buffer)
+	if _, err := io.Copy(b, e.Body); err != nil {
+		return nil, err
+	}
+	e.Body = b
+	return b, nil
+}
+
+func matchBody(e *message.Entity, substr string) (bool, error) {
+	if s, ok := e.Body.(fmt.Stringer); ok {
+		return matchString(s.String(), substr), nil
+	}
+
+	b, err := bufferBody(e)
+	if err != nil {
+		return false, err
+	}
+	return matchString(b.String(), substr), nil
+}
+
+type lengther interface {
+	Len() int
+}
+
+type countWriter struct {
+	N int
+}
+
+func (w *countWriter) Write(b []byte) (int, error) {
+	w.N += len(b)
+	return len(b), nil
+}
+
+func bodyLen(e *message.Entity) (int, error) {
+	headerSize := countWriter{}
+	textproto.WriteHeader(&headerSize, e.Header.Header)
+
+	if l, ok := e.Body.(lengther); ok {
+		return l.Len() + headerSize.N, nil
+	}
+
+	b, err := bufferBody(e)
+	if err != nil {
+		return 0, err
+	}
+	return b.Len() + headerSize.N, nil
+}
+
+// Match returns true if a message and its metadata matches the provided
+// criteria.
+func Match(e *message.Entity, seqNum, uid uint32, date time.Time, flags []string, c *imap.SearchCriteria) (bool, error) {
+	// TODO: support encoded header fields for Bcc, Cc, From, To
+	// TODO: add header size for Larger and Smaller
+
+	h := mail.Header{Header: e.Header}
+
+	if !c.SentBefore.IsZero() || !c.SentSince.IsZero() {
+		t, err := h.Date()
+		if err != nil {
+			return false, err
+		}
+		t = time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, time.UTC)
+
+		if !c.SentBefore.IsZero() && !t.Before(c.SentBefore) {
+			return false, nil
+		}
+		if !c.SentSince.IsZero() && t.Before(c.SentSince) {
+			return false, nil
+		}
+	}
+
+	for key, wantValues := range c.Header {
+		ok := e.Header.Has(key)
+		for _, wantValue := range wantValues {
+			if wantValue == "" && !ok {
+				return false, nil
+			}
+			if wantValue != "" {
+				ok := false
+				values := e.Header.FieldsByKey(key)
+				for values.Next() {
+					decoded, _ := values.Text()
+					if matchString(decoded, wantValue) {
+						ok = true
+						break
+					}
+				}
+				if !ok {
+					return false, nil
+				}
+			}
+		}
+	}
+	for _, body := range c.Body {
+		if ok, err := matchBody(e, body); err != nil || !ok {
+			return false, err
+		}
+	}
+	for _, text := range c.Text {
+		headerMatch := false
+		for f := e.Header.Fields(); f.Next(); {
+			decoded, err := f.Text()
+			if err != nil {
+				continue
+			}
+			if strings.Contains(f.Key()+": "+decoded, text) {
+				headerMatch = true
+			}
+		}
+		if ok, err := matchBody(e, text); err != nil || !ok && !headerMatch {
+			return false, err
+		}
+	}
+
+	if c.Larger > 0 || c.Smaller > 0 {
+		n, err := bodyLen(e)
+		if err != nil {
+			return false, err
+		}
+
+		if c.Larger > 0 && uint32(n) <= c.Larger {
+			return false, nil
+		}
+		if c.Smaller > 0 && uint32(n) >= c.Smaller {
+			return false, nil
+		}
+	}
+
+	if !c.Since.IsZero() || !c.Before.IsZero() {
+		if !matchDate(date, c) {
+			return false, nil
+		}
+	}
+
+	if c.WithFlags != nil || c.WithoutFlags != nil {
+		if !matchFlags(flags, c) {
+			return false, nil
+		}
+	}
+
+	if c.SeqNum != nil || c.Uid != nil {
+		if !matchSeqNumAndUid(seqNum, uid, c) {
+			return false, nil
+		}
+	}
+
+	for _, not := range c.Not {
+		ok, err := Match(e, seqNum, uid, date, flags, not)
+		if err != nil || ok {
+			return false, err
+		}
+	}
+	for _, or := range c.Or {
+		ok1, err := Match(e, seqNum, uid, date, flags, or[0])
+		if err != nil {
+			return ok1, err
+		}
+
+		ok2, err := Match(e, seqNum, uid, date, flags, or[1])
+		if err != nil || (!ok1 && !ok2) {
+			return false, err
+		}
+	}
+
+	return true, nil
+}
+
+func matchFlags(flags []string, c *imap.SearchCriteria) bool {
+	flagsMap := make(map[string]bool)
+	for _, f := range flags {
+		flagsMap[f] = true
+	}
+
+	for _, f := range c.WithFlags {
+		if !flagsMap[f] {
+			return false
+		}
+	}
+	for _, f := range c.WithoutFlags {
+		if flagsMap[f] {
+			return false
+		}
+	}
+
+	return true
+}
+
+func matchSeqNumAndUid(seqNum uint32, uid uint32, c *imap.SearchCriteria) bool {
+	if c.SeqNum != nil && !c.SeqNum.Contains(seqNum) {
+		return false
+	}
+	if c.Uid != nil && !c.Uid.Contains(uid) {
+		return false
+	}
+	return true
+}
+
+func matchDate(date time.Time, c *imap.SearchCriteria) bool {
+	// We discard time zone information by setting it to UTC.
+	// RFC 3501 explicitly requires zone unaware date comparison.
+	date = time.Date(date.Year(), date.Month(), date.Day(), 0, 0, 0, 0, time.UTC)
+
+	if !c.Since.IsZero() && !date.After(c.Since) {
+		return false
+	}
+	if !c.Before.IsZero() && !date.Before(c.Before) {
+		return false
+	}
+	return true
+}

backend/backendutil/search_test.go

@@ -0,0 +1,432 @@
+package backendutil
+
+import (
+	"net/textproto"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-message"
+)
+
+var testInternalDate = time.Unix(1483997966, 0)
+
+var matchTests = []struct {
+	criteria *imap.SearchCriteria
+	seqNum   uint32
+	uid      uint32
+	date     time.Time
+	flags    []string
+	res      bool
+}{
+	{
+		criteria: &imap.SearchCriteria{
+			Header: textproto.MIMEHeader{"From": {"Mitsuha"}},
+		},
+		res: true,
+	},
+	{
+		criteria: &imap.SearchCriteria{
+			Header: textproto.MIMEHeader{"To": {"Mitsuha"}},
+		},
+		res: false,
+	},
+	{
+		criteria: &imap.SearchCriteria{SentBefore: testDate.Add(48 * time.Hour)},
+		res:      true,
+	},
+	{
+		criteria: &imap.SearchCriteria{
+			Not: []*imap.SearchCriteria{{SentSince: testDate.Add(48 * time.Hour)}},
+		},
+		res: true,
+	},
+	{
+		criteria: &imap.SearchCriteria{
+			Not: []*imap.SearchCriteria{{Body: []string{"name"}}},
+		},
+		res: false,
+	},
+	{
+		criteria: &imap.SearchCriteria{
+			Text: []string{"name"},
+		},
+		res: true,
+	},
+	{
+		criteria: &imap.SearchCriteria{
+			Or: [][2]*imap.SearchCriteria{{
+				{Text: []string{"i'm not in the text"}},
+				{Body: []string{"i'm not in the body"}},
+			}},
+		},
+		res: false,
+	},
+	{
+		criteria: &imap.SearchCriteria{
+			Header: textproto.MIMEHeader{"Message-Id": {"42@example.org"}},
+		},
+		res: true,
+	},
+	{
+		criteria: &imap.SearchCriteria{
+			Header: textproto.MIMEHeader{"Message-Id": {"43@example.org"}},
+		},
+		res: false,
+	},
+	{
+		criteria: &imap.SearchCriteria{
+			Header: textproto.MIMEHeader{"Message-Id": {""}},
+		},
+		res: true,
+	},
+	{
+		criteria: &imap.SearchCriteria{
+			Header: textproto.MIMEHeader{"Totally-Not-Reply-To": {""}},
+		},
+		res: false,
+	},
+	{
+		criteria: &imap.SearchCriteria{
+			Larger: 10,
+		},
+		res: true,
+	},
+	{
+		criteria: &imap.SearchCriteria{
+			Smaller: 10,
+		},
+		res: false,
+	},
+	{
+		criteria: &imap.SearchCriteria{
+			Header: textproto.MIMEHeader{"Subject": {"your"}},
+		},
+		res: true,
+	},
+	{
+		criteria: &imap.SearchCriteria{
+			Header: textproto.MIMEHeader{"Subject": {"Taki"}},
+		},
+		res: false,
+	},
+	{
+		flags: []string{imap.SeenFlag},
+		criteria: &imap.SearchCriteria{
+			WithFlags:    []string{imap.SeenFlag},
+			WithoutFlags: []string{imap.FlaggedFlag},
+		},
+		res: true,
+	},
+	{
+		flags: []string{imap.SeenFlag},
+		criteria: &imap.SearchCriteria{
+			WithFlags:    []string{imap.DraftFlag},
+			WithoutFlags: []string{imap.FlaggedFlag},
+		},
+		res: false,
+	},
+	{
+		flags: []string{imap.SeenFlag, imap.FlaggedFlag},
+		criteria: &imap.SearchCriteria{
+			WithFlags:    []string{imap.SeenFlag},
+			WithoutFlags: []string{imap.FlaggedFlag},
+		},
+		res: false,
+	},
+	{
+		flags: []string{imap.SeenFlag, imap.FlaggedFlag},
+		criteria: &imap.SearchCriteria{
+			Or: [][2]*imap.SearchCriteria{{
+				{WithFlags: []string{imap.DraftFlag}},
+				{WithoutFlags: []string{imap.SeenFlag}},
+			}},
+		},
+		res: false,
+	},
+	{
+		flags: []string{imap.SeenFlag, imap.FlaggedFlag},
+		criteria: &imap.SearchCriteria{
+			Not: []*imap.SearchCriteria{
+				{WithFlags: []string{imap.SeenFlag}},
+			},
+		},
+		res: false,
+	},
+	{
+		seqNum: 42,
+		uid:    69,
+		criteria: &imap.SearchCriteria{
+			Or: [][2]*imap.SearchCriteria{{
+				{
+					Uid: new(imap.SeqSet),
+					Not: []*imap.SearchCriteria{{SeqNum: new(imap.SeqSet)}},
+				},
+				{
+					SeqNum: new(imap.SeqSet),
+				},
+			}},
+		},
+		res: false,
+	},
+	{
+		seqNum: 42,
+		uid:    69,
+		criteria: &imap.SearchCriteria{
+			Or: [][2]*imap.SearchCriteria{{
+				{
+					Uid: &imap.SeqSet{Set: []imap.Seq{{69, 69}}},
+					Not: []*imap.SearchCriteria{{SeqNum: new(imap.SeqSet)}},
+				},
+				{
+					SeqNum: new(imap.SeqSet),
+				},
+			}},
+		},
+		res: true,
+	},
+	{
+		seqNum: 42,
+		uid:    69,
+		criteria: &imap.SearchCriteria{
+			Or: [][2]*imap.SearchCriteria{{
+				{
+					Uid: &imap.SeqSet{Set: []imap.Seq{{69, 69}}},
+					Not: []*imap.SearchCriteria{{
+						SeqNum: &imap.SeqSet{Set: []imap.Seq{imap.Seq{42, 42}}},
+					}},
+				},
+				{
+					SeqNum: new(imap.SeqSet),
+				},
+			}},
+		},
+		res: false,
+	},
+	{
+		seqNum: 42,
+		uid:    69,
+		criteria: &imap.SearchCriteria{
+			Or: [][2]*imap.SearchCriteria{{
+				{
+					Uid: &imap.SeqSet{Set: []imap.Seq{{69, 69}}},
+					Not: []*imap.SearchCriteria{{
+						SeqNum: &imap.SeqSet{Set: []imap.Seq{{42, 42}}},
+					}},
+				},
+				{
+					SeqNum: &imap.SeqSet{Set: []imap.Seq{{42, 42}}},
+				},
+			}},
+		},
+		res: true,
+	},
+	{
+		date: testInternalDate,
+		criteria: &imap.SearchCriteria{
+			Or: [][2]*imap.SearchCriteria{{
+				{
+					Since: testInternalDate.Add(48 * time.Hour),
+					Not: []*imap.SearchCriteria{{
+						Since: testInternalDate.Add(48 * time.Hour),
+					}},
+				},
+				{
+					Before: testInternalDate.Add(-48 * time.Hour),
+				},
+			}},
+		},
+		res: false,
+	},
+	{
+		date: testInternalDate,
+		criteria: &imap.SearchCriteria{
+			Or: [][2]*imap.SearchCriteria{{
+				{
+					Since: testInternalDate.Add(-48 * time.Hour),
+					Not: []*imap.SearchCriteria{{
+						Since: testInternalDate.Add(48 * time.Hour),
+					}},
+				},
+				{
+					Before: testInternalDate.Add(-48 * time.Hour),
+				},
+			}},
+		},
+		res: true,
+	},
+	{
+		date: testInternalDate,
+		criteria: &imap.SearchCriteria{
+			Or: [][2]*imap.SearchCriteria{{
+				{
+					Since: testInternalDate.Add(-48 * time.Hour),
+					Not: []*imap.SearchCriteria{{
+						Since: testInternalDate.Add(-48 * time.Hour),
+					}},
+				},
+				{
+					Before: testInternalDate.Add(-48 * time.Hour),
+				},
+			}},
+		},
+		res: false,
+	},
+	{
+		date: testInternalDate,
+		criteria: &imap.SearchCriteria{
+			Or: [][2]*imap.SearchCriteria{{
+				{
+					Since: testInternalDate.Add(-48 * time.Hour),
+					Not: []*imap.SearchCriteria{{
+						Since: testInternalDate.Add(-48 * time.Hour),
+					}},
+				},
+				{
+					Before: testInternalDate.Add(48 * time.Hour),
+				},
+			}},
+		},
+		res: true,
+	},
+}
+
+func TestMatch(t *testing.T) {
+	for i, test := range matchTests {
+		e, err := message.Read(strings.NewReader(testMailString))
+		if err != nil {
+			t.Fatal("Expected no error while reading entity, got:", err)
+		}
+
+		ok, err := Match(e, test.seqNum, test.uid, test.date, test.flags, test.criteria)
+		if err != nil {
+			t.Fatal("Expected no error while matching entity, got:", err)
+		}
+
+		if test.res && !ok {
+			t.Errorf("Expected #%v to match search criteria", i+1)
+		}
+		if !test.res && ok {
+			t.Errorf("Expected #%v not to match search criteria", i+1)
+		}
+	}
+}
+
+func TestMatchEncoded(t *testing.T) {
+	encodedTestMsg := `From: "fox.cpp" <foxcpp@foxcpp.dev>
+To: "fox.cpp" <foxcpp@foxcpp.dev>
+Subject: =?utf-8?B?0J/RgNC+0LLQtdGA0LrQsCE=?=
+Date: Sun, 09 Jun 2019 00:06:43 +0300
+MIME-Version: 1.0
+Message-ID: <a2aeb99e-52dd-40d3-b99f-1fdaad77ed98@foxcpp.dev>
+Content-Type: text/plain; charset=utf-8; format=flowed
+Content-Transfer-Encoding: quoted-printable
+
+=D0=AD=D1=82=D0=BE=D1=82 =D1=82=D0=B5=D0=BA=D1=81=D1=82 =D0=B4=D0=BE=D0=BB=
+=D0=B6=D0=B5=D0=BD =D0=B1=D1=8B=D1=82=D1=8C =D0=B7=D0=B0=D0=BA=D0=BE=D0=B4=
+=D0=B8=D1=80=D0=BE=D0=B2=D0=B0=D0=BD =D0=B2 base64 =D0=B8=D0=BB=D0=B8 quote=
+d-encoding.`
+	e, err := message.Read(strings.NewReader(encodedTestMsg))
+	if err != nil {
+		t.Fatal("Expected no error while reading entity, got:", err)
+	}
+
+	// Check encoded header.
+	crit := imap.SearchCriteria{
+		Header: textproto.MIMEHeader{"Subject": []string{"Проверка!"}},
+	}
+
+	ok, err := Match(e, 0, 0, time.Now(), []string{}, &crit)
+	if err != nil {
+		t.Fatal("Expected no error while matching entity, got:", err)
+	}
+
+	if !ok {
+		t.Error("Expected match for encoded header")
+	}
+
+	// Encoded body.
+	crit = imap.SearchCriteria{
+		Body: []string{"или"},
+	}
+
+	ok, err = Match(e, 0, 0, time.Now(), []string{}, &crit)
+	if err != nil {
+		t.Fatal("Expected no error while matching entity, got:", err)
+	}
+
+	if !ok {
+		t.Error("Expected match for encoded body")
+	}
+}
+
+func TestMatchIssue298Regression(t *testing.T) {
+	raw1 := "Subject: 1\r\n\r\n1"
+	raw2 := "Subject: 2\r\n\r\n22"
+	raw3 := "Subject: 3\r\n\r\n333"
+	e1, err := message.Read(strings.NewReader(raw1))
+	if err != nil {
+		t.Fatal("Expected no error while reading entity, got:", err)
+	}
+	e2, err := message.Read(strings.NewReader(raw2))
+	if err != nil {
+		t.Fatal("Expected no error while reading entity, got:", err)
+	}
+	e3, err := message.Read(strings.NewReader(raw3))
+	if err != nil {
+		t.Fatal("Expected no error while reading entity, got:", err)
+	}
+
+	// Search for body size > 15 ("LARGER 15"), which should match messages #2 and #3
+	criteria := &imap.SearchCriteria{
+		Larger: 15,
+	}
+	ok1, err := Match(e1, 1, 101, time.Now(), nil, criteria)
+	if err != nil {
+		t.Fatal("Expected no error while matching entity, got:", err)
+	}
+	if ok1 {
+		t.Errorf("Expected message #1 to not match search criteria")
+	}
+	ok2, err := Match(e2, 2, 102, time.Now(), nil, criteria)
+	if err != nil {
+		t.Fatal("Expected no error while matching entity, got:", err)
+	}
+	if !ok2 {
+		t.Errorf("Expected message #2 to match search criteria")
+	}
+	ok3, err := Match(e3, 3, 103, time.Now(), nil, criteria)
+	if err != nil {
+		t.Fatal("Expected no error while matching entity, got:", err)
+	}
+	if !ok3 {
+		t.Errorf("Expected message #3 to match search criteria")
+	}
+
+	// Search for body size < 17 ("SMALLER 17"), which should match messages #1 and #2
+	criteria = &imap.SearchCriteria{
+		Smaller: 17,
+	}
+	ok1, err = Match(e1, 1, 101, time.Now(), nil, criteria)
+	if err != nil {
+		t.Fatal("Expected no error while matching entity, got:", err)
+	}
+	if !ok1 {
+		t.Errorf("Expected message #1 to match search criteria")
+	}
+	ok2, err = Match(e2, 2, 102, time.Now(), nil, criteria)
+	if err != nil {
+		t.Fatal("Expected no error while matching entity, got:", err)
+	}
+	if !ok2 {
+		t.Errorf("Expected message #2 to match search criteria")
+	}
+	ok3, err = Match(e3, 3, 103, time.Now(), nil, criteria)
+	if err != nil {
+		t.Fatal("Expected no error while matching entity, got:", err)
+	}
+	if ok3 {
+		t.Errorf("Expected message #3 to not match search criteria")
+	}
+}

backend/mailbox.go

@@ -0,0 +1,78 @@
+package backend
+
+import (
+	"time"
+
+	"github.com/emersion/go-imap"
+)
+
+// Mailbox represents a mailbox belonging to a user in the mail storage system.
+// A mailbox operation always deals with messages.
+type Mailbox interface {
+	// Name returns this mailbox name.
+	Name() string
+
+	// Info returns this mailbox info.
+	Info() (*imap.MailboxInfo, error)
+
+	// Status returns this mailbox status. The fields Name, Flags, PermanentFlags
+	// and UnseenSeqNum in the returned MailboxStatus must be always populated.
+	// This function does not affect the state of any messages in the mailbox. See
+	// RFC 3501 section 6.3.10 for a list of items that can be requested.
+	Status(items []imap.StatusItem) (*imap.MailboxStatus, error)
+
+	// SetSubscribed adds or removes the mailbox to the server's set of "active"
+	// or "subscribed" mailboxes.
+	SetSubscribed(subscribed bool) error
+
+	// Check requests a checkpoint of the currently selected mailbox. A checkpoint
+	// refers to any implementation-dependent housekeeping associated with the
+	// mailbox (e.g., resolving the server's in-memory state of the mailbox with
+	// the state on its disk). A checkpoint MAY take a non-instantaneous amount of
+	// real time to complete. If a server implementation has no such housekeeping
+	// considerations, CHECK is equivalent to NOOP.
+	Check() error
+
+	// ListMessages returns a list of messages. seqset must be interpreted as UIDs
+	// if uid is set to true and as message sequence numbers otherwise. See RFC
+	// 3501 section 6.4.5 for a list of items that can be requested.
+	//
+	// Messages must be sent to ch. When the function returns, ch must be closed.
+	ListMessages(uid bool, seqset *imap.SeqSet, items []imap.FetchItem, ch chan<- *imap.Message) error
+
+	// SearchMessages searches messages. The returned list must contain UIDs if
+	// uid is set to true, or sequence numbers otherwise.
+	SearchMessages(uid bool, criteria *imap.SearchCriteria) ([]uint32, error)
+
+	// CreateMessage appends a new message to this mailbox. The \Recent flag will
+	// be added no matter flags is empty or not. If date is nil, the current time
+	// will be used.
+	//
+	// If the Backend implements Updater, it must notify the client immediately
+	// via a mailbox update.
+	CreateMessage(flags []string, date time.Time, body imap.Literal) error
+
+	// UpdateMessagesFlags alters flags for the specified message(s).
+	//
+	// If the Backend implements Updater, it must notify the client immediately
+	// via a message update.
+	UpdateMessagesFlags(uid bool, seqset *imap.SeqSet, operation imap.FlagsOp, flags []string) error
+
+	// CopyMessages copies the specified message(s) to the end of the specified
+	// destination mailbox. The flags and internal date of the message(s) SHOULD
+	// be preserved, and the Recent flag SHOULD be set, in the copy.
+	//
+	// If the destination mailbox does not exist, a server SHOULD return an error.
+	// It SHOULD NOT automatically create the mailbox.
+	//
+	// If the Backend implements Updater, it must notify the client immediately
+	// via a mailbox update.
+	CopyMessages(uid bool, seqset *imap.SeqSet, dest string) error
+
+	// Expunge permanently removes all messages that have the \Deleted flag set
+	// from the currently selected mailbox.
+	//
+	// If the Backend implements Updater, it must notify the client immediately
+	// via an expunge update.
+	Expunge() error
+}

backend/memory/backend.go

@@ -0,0 +1,78 @@
+// A memory backend.
+package memory
+
+import (
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/backend"
+)
+
+type Backend struct {
+	users map[string]*User
+}
+
+func (be *Backend) Login(_ *imap.ConnInfo, username, password string) (backend.User, error) {
+	user, ok := be.users[username]
+	if ok && user.password == password {
+		return user, nil
+	}
+
+	return nil, errors.New("Bad username or password")
+}
+
+func New() *Backend {
+	user := &User{username: "username", password: "password"}
+
+	body := "From: contact@example.org\r\n" +
+		"To: contact@example.org\r\n" +
+		"Subject: A little message, just for you\r\n" +
+		"Date: Wed, 11 May 2016 14:31:59 +0000\r\n" +
+		"Message-ID: <0000000@localhost/>\r\n" +
+		"Content-Type: text/plain\r\n" +
+		"\r\n" +
+		"Hi there :)"
+
+	user.mailboxes = map[string]*Mailbox{
+		"INBOX": {
+			name: "INBOX",
+			user: user,
+			Messages: []*Message{
+				{
+					Uid:   6,
+					Date:  time.Now(),
+					Flags: []string{"\\Seen"},
+					Size:  uint32(len(body)),
+					Body:  []byte(body),
+				},
+			},
+		},
+	}
+
+	return &Backend{
+		users: map[string]*User{user.username: user},
+	}
+}
+
+// NewUser adds a user to the backend.
+func (be *Backend) NewUser(username, password string) (*User, error) {
+	_, ok := be.users[username]
+	if ok {
+		return nil, fmt.Errorf("user %s is already defined.", username)
+	}
+	u := &User{username: username, password: password, mailboxes: make(map[string]*Mailbox)}
+	be.users[username] = u
+	return u, nil
+}
+
+// DeleteUser removes a user from the backend.
+func (be *Backend) DeleteUser(username string) error {
+	_, ok := be.users[username]
+	if !ok {
+		return fmt.Errorf("user %s is not defined.", username)
+	}
+	delete(be.users, username)
+	return nil
+}

backend/memory/mailbox.go

@@ -0,0 +1,243 @@
+package memory
+
+import (
+	"io/ioutil"
+	"time"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/backend"
+	"github.com/emersion/go-imap/backend/backendutil"
+)
+
+var Delimiter = "/"
+
+type Mailbox struct {
+	Subscribed bool
+	Messages   []*Message
+
+	name string
+	user *User
+}
+
+func (mbox *Mailbox) Name() string {
+	return mbox.name
+}
+
+func (mbox *Mailbox) Info() (*imap.MailboxInfo, error) {
+	info := &imap.MailboxInfo{
+		Delimiter: Delimiter,
+		Name:      mbox.name,
+	}
+	return info, nil
+}
+
+func (mbox *Mailbox) uidNext() uint32 {
+	var uid uint32
+	for _, msg := range mbox.Messages {
+		if msg.Uid > uid {
+			uid = msg.Uid
+		}
+	}
+	uid++
+	return uid
+}
+
+func (mbox *Mailbox) flags() []string {
+	flagsMap := make(map[string]bool)
+	for _, msg := range mbox.Messages {
+		for _, f := range msg.Flags {
+			if !flagsMap[f] {
+				flagsMap[f] = true
+			}
+		}
+	}
+
+	var flags []string
+	for f := range flagsMap {
+		flags = append(flags, f)
+	}
+	return flags
+}
+
+func (mbox *Mailbox) unseenSeqNum() uint32 {
+	for i, msg := range mbox.Messages {
+		seqNum := uint32(i + 1)
+
+		seen := false
+		for _, flag := range msg.Flags {
+			if flag == imap.SeenFlag {
+				seen = true
+				break
+			}
+		}
+
+		if !seen {
+			return seqNum
+		}
+	}
+	return 0
+}
+
+func (mbox *Mailbox) Status(items []imap.StatusItem) (*imap.MailboxStatus, error) {
+	status := imap.NewMailboxStatus(mbox.name, items)
+	status.Flags = mbox.flags()
+	status.PermanentFlags = []string{"\\*"}
+	status.UnseenSeqNum = mbox.unseenSeqNum()
+
+	for _, name := range items {
+		switch name {
+		case imap.StatusMessages:
+			status.Messages = uint32(len(mbox.Messages))
+		case imap.StatusUidNext:
+			status.UidNext = mbox.uidNext()
+		case imap.StatusUidValidity:
+			status.UidValidity = 1
+		case imap.StatusRecent:
+			status.Recent = 0 // TODO
+		case imap.StatusUnseen:
+			status.Unseen = 0 // TODO
+		}
+	}
+
+	return status, nil
+}
+
+func (mbox *Mailbox) SetSubscribed(subscribed bool) error {
+	mbox.Subscribed = subscribed
+	return nil
+}
+
+func (mbox *Mailbox) Check() error {
+	return nil
+}
+
+func (mbox *Mailbox) ListMessages(uid bool, seqSet *imap.SeqSet, items []imap.FetchItem, ch chan<- *imap.Message) error {
+	defer close(ch)
+
+	for i, msg := range mbox.Messages {
+		seqNum := uint32(i + 1)
+
+		var id uint32
+		if uid {
+			id = msg.Uid
+		} else {
+			id = seqNum
+		}
+		if !seqSet.Contains(id) {
+			continue
+		}
+
+		m, err := msg.Fetch(seqNum, items)
+		if err != nil {
+			continue
+		}
+
+		ch <- m
+	}
+
+	return nil
+}
+
+func (mbox *Mailbox) SearchMessages(uid bool, criteria *imap.SearchCriteria) ([]uint32, error) {
+	var ids []uint32
+	for i, msg := range mbox.Messages {
+		seqNum := uint32(i + 1)
+
+		ok, err := msg.Match(seqNum, criteria)
+		if err != nil || !ok {
+			continue
+		}
+
+		var id uint32
+		if uid {
+			id = msg.Uid
+		} else {
+			id = seqNum
+		}
+		ids = append(ids, id)
+	}
+	return ids, nil
+}
+
+func (mbox *Mailbox) CreateMessage(flags []string, date time.Time, body imap.Literal) error {
+	if date.IsZero() {
+		date = time.Now()
+	}
+
+	b, err := ioutil.ReadAll(body)
+	if err != nil {
+		return err
+	}
+
+	mbox.Messages = append(mbox.Messages, &Message{
+		Uid:   mbox.uidNext(),
+		Date:  date,
+		Size:  uint32(len(b)),
+		Flags: flags,
+		Body:  b,
+	})
+	return nil
+}
+
+func (mbox *Mailbox) UpdateMessagesFlags(uid bool, seqset *imap.SeqSet, op imap.FlagsOp, flags []string) error {
+	for i, msg := range mbox.Messages {
+		var id uint32
+		if uid {
+			id = msg.Uid
+		} else {
+			id = uint32(i + 1)
+		}
+		if !seqset.Contains(id) {
+			continue
+		}
+
+		msg.Flags = backendutil.UpdateFlags(msg.Flags, op, flags)
+	}
+
+	return nil
+}
+
+func (mbox *Mailbox) CopyMessages(uid bool, seqset *imap.SeqSet, destName string) error {
+	dest, ok := mbox.user.mailboxes[destName]
+	if !ok {
+		return backend.ErrNoSuchMailbox
+	}
+
+	for i, msg := range mbox.Messages {
+		var id uint32
+		if uid {
+			id = msg.Uid
+		} else {
+			id = uint32(i + 1)
+		}
+		if !seqset.Contains(id) {
+			continue
+		}
+
+		msgCopy := *msg
+		msgCopy.Uid = dest.uidNext()
+		dest.Messages = append(dest.Messages, &msgCopy)
+	}
+
+	return nil
+}
+
+func (mbox *Mailbox) Expunge() error {
+	for i := len(mbox.Messages) - 1; i >= 0; i-- {
+		msg := mbox.Messages[i]
+
+		deleted := false
+		for _, flag := range msg.Flags {
+			if flag == imap.DeletedFlag {
+				deleted = true
+				break
+			}
+		}
+
+		if deleted {
+			mbox.Messages = append(mbox.Messages[:i], mbox.Messages[i+1:]...)
+		}
+	}
+
+	return nil
+}

backend/memory/message.go

@@ -0,0 +1,74 @@
+package memory
+
+import (
+	"bufio"
+	"bytes"
+	"io"
+	"time"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/backend/backendutil"
+	"github.com/emersion/go-message"
+	"github.com/emersion/go-message/textproto"
+)
+
+type Message struct {
+	Uid   uint32
+	Date  time.Time
+	Size  uint32
+	Flags []string
+	Body  []byte
+}
+
+func (m *Message) entity() (*message.Entity, error) {
+	return message.Read(bytes.NewReader(m.Body))
+}
+
+func (m *Message) headerAndBody() (textproto.Header, io.Reader, error) {
+	body := bufio.NewReader(bytes.NewReader(m.Body))
+	hdr, err := textproto.ReadHeader(body)
+	return hdr, body, err
+}
+
+func (m *Message) Fetch(seqNum uint32, items []imap.FetchItem) (*imap.Message, error) {
+	fetched := imap.NewMessage(seqNum, items)
+	for _, item := range items {
+		switch item {
+		case imap.FetchEnvelope:
+			hdr, _, _ := m.headerAndBody()
+			fetched.Envelope, _ = backendutil.FetchEnvelope(hdr)
+		case imap.FetchBody, imap.FetchBodyStructure:
+			hdr, body, _ := m.headerAndBody()
+			fetched.BodyStructure, _ = backendutil.FetchBodyStructure(hdr, body, item == imap.FetchBodyStructure)
+		case imap.FetchFlags:
+			fetched.Flags = m.Flags
+		case imap.FetchInternalDate:
+			fetched.InternalDate = m.Date
+		case imap.FetchRFC822Size:
+			fetched.Size = m.Size
+		case imap.FetchUid:
+			fetched.Uid = m.Uid
+		default:
+			section, err := imap.ParseBodySectionName(item)
+			if err != nil {
+				break
+			}
+
+			body := bufio.NewReader(bytes.NewReader(m.Body))
+			hdr, err := textproto.ReadHeader(body)
+			if err != nil {
+				return nil, err
+			}
+
+			l, _ := backendutil.FetchBodySection(hdr, body, section)
+			fetched.Body[section] = l
+		}
+	}
+
+	return fetched, nil
+}
+
+func (m *Message) Match(seqNum uint32, c *imap.SearchCriteria) (bool, error) {
+	e, _ := m.entity()
+	return backendutil.Match(e, seqNum, m.Uid, m.Date, m.Flags, c)
+}

backend/memory/user.go

@@ -0,0 +1,82 @@
+package memory
+
+import (
+	"errors"
+
+	"github.com/emersion/go-imap/backend"
+)
+
+type User struct {
+	username  string
+	password  string
+	mailboxes map[string]*Mailbox
+}
+
+func (u *User) Username() string {
+	return u.username
+}
+
+func (u *User) ListMailboxes(subscribed bool) (mailboxes []backend.Mailbox, err error) {
+	for _, mailbox := range u.mailboxes {
+		if subscribed && !mailbox.Subscribed {
+			continue
+		}
+
+		mailboxes = append(mailboxes, mailbox)
+	}
+	return
+}
+
+func (u *User) GetMailbox(name string) (mailbox backend.Mailbox, err error) {
+	mailbox, ok := u.mailboxes[name]
+	if !ok {
+		err = errors.New("No such mailbox")
+	}
+	return
+}
+
+func (u *User) CreateMailbox(name string) error {
+	if _, ok := u.mailboxes[name]; ok {
+		return errors.New("Mailbox already exists")
+	}
+
+	u.mailboxes[name] = &Mailbox{name: name, user: u}
+	return nil
+}
+
+func (u *User) DeleteMailbox(name string) error {
+	if name == "INBOX" {
+		return errors.New("Cannot delete INBOX")
+	}
+	if _, ok := u.mailboxes[name]; !ok {
+		return errors.New("No such mailbox")
+	}
+
+	delete(u.mailboxes, name)
+	return nil
+}
+
+func (u *User) RenameMailbox(existingName, newName string) error {
+	mbox, ok := u.mailboxes[existingName]
+	if !ok {
+		return errors.New("No such mailbox")
+	}
+
+	u.mailboxes[newName] = &Mailbox{
+		name:     newName,
+		Messages: mbox.Messages,
+		user:     u,
+	}
+
+	mbox.Messages = nil
+
+	if existingName != "INBOX" {
+		delete(u.mailboxes, existingName)
+	}
+
+	return nil
+}
+
+func (u *User) Logout() error {
+	return nil
+}

backend/move.go

@@ -0,0 +1,19 @@
+package backend
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// MoveMailbox is a mailbox that supports moving messages.
+type MoveMailbox interface {
+	Mailbox
+
+	// Move the specified message(s) to the end of the specified destination
+	// mailbox. This means that a new message is created in the target mailbox
+	// with a new UID, the original message is removed from the source mailbox,
+	// and it appears to the client as a single action.
+	//
+	// If the destination mailbox does not exist, a server SHOULD return an error.
+	// It SHOULD NOT automatically create the mailbox.
+	MoveMessages(uid bool, seqset *imap.SeqSet, dest string) error
+}

backend/updates.go

@@ -0,0 +1,98 @@
+package backend
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// Update contains user and mailbox information about an unilateral backend
+// update.
+type Update interface {
+	// The user targeted by this update. If empty, all connected users will
+	// be notified.
+	Username() string
+	// The mailbox targeted by this update. If empty, the update targets all
+	// mailboxes.
+	Mailbox() string
+	// Done returns a channel that is closed when the update has been broadcast to
+	// all clients.
+	Done() chan struct{}
+}
+
+// NewUpdate creates a new update.
+func NewUpdate(username, mailbox string) Update {
+	return &update{
+		username: username,
+		mailbox:  mailbox,
+	}
+}
+
+type update struct {
+	username string
+	mailbox  string
+	done     chan struct{}
+}
+
+func (u *update) Username() string {
+	return u.username
+}
+
+func (u *update) Mailbox() string {
+	return u.mailbox
+}
+
+func (u *update) Done() chan struct{} {
+	if u.done == nil {
+		u.done = make(chan struct{})
+	}
+	return u.done
+}
+
+// StatusUpdate is a status update. See RFC 3501 section 7.1 for a list of
+// status responses.
+type StatusUpdate struct {
+	Update
+	*imap.StatusResp
+}
+
+// MailboxUpdate is a mailbox update.
+type MailboxUpdate struct {
+	Update
+	*imap.MailboxStatus
+}
+
+// MailboxInfoUpdate is a maiblox info update.
+type MailboxInfoUpdate struct {
+	Update
+	*imap.MailboxInfo
+}
+
+// MessageUpdate is a message update.
+type MessageUpdate struct {
+	Update
+	*imap.Message
+}
+
+// ExpungeUpdate is an expunge update.
+type ExpungeUpdate struct {
+	Update
+	SeqNum uint32
+}
+
+// BackendUpdater is a Backend that implements Updater is able to send
+// unilateral backend updates. Backends not implementing this interface don't
+// correctly send unilateral updates, for instance if a user logs in from two
+// connections and deletes a message from one of them, the over is not aware
+// that such a mesage has been deleted. More importantly, backends implementing
+// Updater can notify the user for external updates such as new message
+// notifications.
+type BackendUpdater interface {
+	// Updates returns a set of channels where updates are sent to.
+	Updates() <-chan Update
+}
+
+// MailboxPoller is a Mailbox that is able to poll updates for new messages or
+// message status updates during a period of inactivity.
+type MailboxPoller interface {
+	// Poll requests mailbox updates.
+	Poll() error
+}

backend/user.go

@@ -0,0 +1,92 @@
+package backend
+
+import "errors"
+
+var (
+	// ErrNoSuchMailbox is returned by User.GetMailbox, User.DeleteMailbox and
+	// User.RenameMailbox when retrieving, deleting or renaming a mailbox that
+	// doesn't exist.
+	ErrNoSuchMailbox = errors.New("No such mailbox")
+	// ErrMailboxAlreadyExists is returned by User.CreateMailbox and
+	// User.RenameMailbox when creating or renaming mailbox that already exists.
+	ErrMailboxAlreadyExists = errors.New("Mailbox already exists")
+)
+
+// User represents a user in the mail storage system. A user operation always
+// deals with mailboxes.
+type User interface {
+	// Username returns this user's username.
+	Username() string
+
+	// ListMailboxes returns a list of mailboxes belonging to this user. If
+	// subscribed is set to true, only returns subscribed mailboxes.
+	ListMailboxes(subscribed bool) ([]Mailbox, error)
+
+	// GetMailbox returns a mailbox. If it doesn't exist, it returns
+	// ErrNoSuchMailbox.
+	GetMailbox(name string) (Mailbox, error)
+
+	// CreateMailbox creates a new mailbox.
+	//
+	// If the mailbox already exists, an error must be returned. If the mailbox
+	// name is suffixed with the server's hierarchy separator character, this is a
+	// declaration that the client intends to create mailbox names under this name
+	// in the hierarchy.
+	//
+	// If the server's hierarchy separator character appears elsewhere in the
+	// name, the server SHOULD create any superior hierarchical names that are
+	// needed for the CREATE command to be successfully completed.  In other
+	// words, an attempt to create "foo/bar/zap" on a server in which "/" is the
+	// hierarchy separator character SHOULD create foo/ and foo/bar/ if they do
+	// not already exist.
+	//
+	// If a new mailbox is created with the same name as a mailbox which was
+	// deleted, its unique identifiers MUST be greater than any unique identifiers
+	// used in the previous incarnation of the mailbox UNLESS the new incarnation
+	// has a different unique identifier validity value.
+	CreateMailbox(name string) error
+
+	// DeleteMailbox permanently remove the mailbox with the given name. It is an
+	// error to // attempt to delete INBOX or a mailbox name that does not exist.
+	//
+	// The DELETE command MUST NOT remove inferior hierarchical names. For
+	// example, if a mailbox "foo" has an inferior "foo.bar" (assuming "." is the
+	// hierarchy delimiter character), removing "foo" MUST NOT remove "foo.bar".
+	//
+	// The value of the highest-used unique identifier of the deleted mailbox MUST
+	// be preserved so that a new mailbox created with the same name will not
+	// reuse the identifiers of the former incarnation, UNLESS the new incarnation
+	// has a different unique identifier validity value.
+	DeleteMailbox(name string) error
+
+	// RenameMailbox changes the name of a mailbox. It is an error to attempt to
+	// rename from a mailbox name that does not exist or to a mailbox name that
+	// already exists.
+	//
+	// If the name has inferior hierarchical names, then the inferior hierarchical
+	// names MUST also be renamed.  For example, a rename of "foo" to "zap" will
+	// rename "foo/bar" (assuming "/" is the hierarchy delimiter character) to
+	// "zap/bar".
+	//
+	// If the server's hierarchy separator character appears in the name, the
+	// server SHOULD create any superior hierarchical names that are needed for
+	// the RENAME command to complete successfully.  In other words, an attempt to
+	// rename "foo/bar/zap" to baz/rag/zowie on a server in which "/" is the
+	// hierarchy separator character SHOULD create baz/ and baz/rag/ if they do
+	// not already exist.
+	//
+	// The value of the highest-used unique identifier of the old mailbox name
+	// MUST be preserved so that a new mailbox created with the same name will not
+	// reuse the identifiers of the former incarnation, UNLESS the new incarnation
+	// has a different unique identifier validity value.
+	//
+	// Renaming INBOX is permitted, and has special behavior.  It moves all
+	// messages in INBOX to a new mailbox with the given name, leaving INBOX
+	// empty.  If the server implementation supports inferior hierarchical names
+	// of INBOX, these are unaffected by a rename of INBOX.
+	RenameMailbox(existingName, newName string) error
+
+	// Logout is called when this User will no longer be used, likely because the
+	// client closed the connection.
+	Logout() error
+}

client/client.go

@@ -0,0 +1,695 @@
+// Package client provides an IMAP client.
+//
+// It is not safe to use the same Client from multiple goroutines. In general,
+// the IMAP protocol doesn't make it possible to send multiple independent
+// IMAP commands on the same connection.
+package client
+
+import (
+	"crypto/tls"
+	"fmt"
+	"io"
+	"log"
+	"net"
+	"os"
+	"sync"
+	"time"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/commands"
+	"github.com/emersion/go-imap/responses"
+)
+
+// errClosed is used when a connection is closed while waiting for a command
+// response.
+var errClosed = fmt.Errorf("imap: connection closed")
+
+// errUnregisterHandler is returned by a response handler to unregister itself.
+var errUnregisterHandler = fmt.Errorf("imap: unregister handler")
+
+// Update is an unilateral server update.
+type Update interface {
+	update()
+}
+
+// StatusUpdate is delivered when a status update is received.
+type StatusUpdate struct {
+	Status *imap.StatusResp
+}
+
+func (u *StatusUpdate) update() {}
+
+// MailboxUpdate is delivered when a mailbox status changes.
+type MailboxUpdate struct {
+	Mailbox *imap.MailboxStatus
+}
+
+func (u *MailboxUpdate) update() {}
+
+// ExpungeUpdate is delivered when a message is deleted.
+type ExpungeUpdate struct {
+	SeqNum uint32
+}
+
+func (u *ExpungeUpdate) update() {}
+
+// MessageUpdate is delivered when a message attribute changes.
+type MessageUpdate struct {
+	Message *imap.Message
+}
+
+func (u *MessageUpdate) update() {}
+
+// Client is an IMAP client.
+type Client struct {
+	conn       *imap.Conn
+	isTLS      bool
+	serverName string
+
+	loggedOut chan struct{}
+	continues chan<- bool
+	upgrading bool
+
+	handlers       []responses.Handler
+	handlersLocker sync.Mutex
+
+	// The current connection state.
+	state imap.ConnState
+	// The selected mailbox, if there is one.
+	mailbox *imap.MailboxStatus
+	// The cached server capabilities.
+	caps map[string]bool
+	// state, mailbox and caps may be accessed in different goroutines. Protect
+	// access.
+	locker sync.Mutex
+
+	// This flag is set when the first search query fails with a BADCHARSET
+	// error. Subsequent queries will be performed with the US-ASCII
+	// charset. According to RFC 3501, SEARCH must only support US-ASCII;
+	// other charsets are optional.
+	utf8SearchUnsupported bool
+
+	// A channel to which unilateral updates from the server will be sent. An
+	// update can be one of: *StatusUpdate, *MailboxUpdate, *MessageUpdate,
+	// *ExpungeUpdate. Note that blocking this channel blocks the whole client,
+	// so it's recommended to use a separate goroutine and a buffered channel to
+	// prevent deadlocks.
+	Updates chan<- Update
+
+	// ErrorLog specifies an optional logger for errors accepting connections and
+	// unexpected behavior from handlers. By default, logging goes to os.Stderr
+	// via the log package's standard logger. The logger must be safe to use
+	// simultaneously from multiple goroutines.
+	ErrorLog imap.Logger
+
+	// Timeout specifies a maximum amount of time to wait on a command.
+	//
+	// A Timeout of zero means no timeout. This is the default.
+	Timeout time.Duration
+}
+
+func (c *Client) registerHandler(h responses.Handler) {
+	if h == nil {
+		return
+	}
+
+	c.handlersLocker.Lock()
+	c.handlers = append(c.handlers, h)
+	c.handlersLocker.Unlock()
+}
+
+func (c *Client) handle(resp imap.Resp) error {
+	c.handlersLocker.Lock()
+	for i := len(c.handlers) - 1; i >= 0; i-- {
+		if err := c.handlers[i].Handle(resp); err != responses.ErrUnhandled {
+			if err == errUnregisterHandler {
+				c.handlers = append(c.handlers[:i], c.handlers[i+1:]...)
+				err = nil
+			}
+			c.handlersLocker.Unlock()
+			return err
+		}
+	}
+	c.handlersLocker.Unlock()
+	return responses.ErrUnhandled
+}
+
+func (c *Client) reader() {
+	defer close(c.loggedOut)
+	// Loop while connected.
+	for {
+		connected, err := c.readOnce()
+		if err != nil {
+			c.ErrorLog.Println("error reading response:", err)
+		}
+		if !connected {
+			return
+		}
+	}
+}
+
+func (c *Client) readOnce() (bool, error) {
+	if c.State() == imap.LogoutState {
+		return false, nil
+	}
+
+	resp, err := imap.ReadResp(c.conn.Reader)
+	if err == io.EOF || c.State() == imap.LogoutState {
+		return false, nil
+	} else if err != nil {
+		if imap.IsParseError(err) {
+			return true, err
+		} else {
+			return false, err
+		}
+	}
+
+	if err := c.handle(resp); err != nil && err != responses.ErrUnhandled {
+		c.ErrorLog.Println("cannot handle response ", resp, err)
+	}
+	return true, nil
+}
+
+func (c *Client) writeReply(reply []byte) error {
+	if _, err := c.conn.Writer.Write(reply); err != nil {
+		return err
+	}
+	// Flush reply
+	return c.conn.Writer.Flush()
+}
+
+type handleResult struct {
+	status *imap.StatusResp
+	err    error
+}
+
+func (c *Client) execute(cmdr imap.Commander, h responses.Handler) (*imap.StatusResp, error) {
+	cmd := cmdr.Command()
+	cmd.Tag = generateTag()
+
+	var replies <-chan []byte
+	if replier, ok := h.(responses.Replier); ok {
+		replies = replier.Replies()
+	}
+
+	if c.Timeout > 0 {
+		err := c.conn.SetDeadline(time.Now().Add(c.Timeout))
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		// It's possible the client had a timeout set from a previous command, but no
+		// longer does. Ensure we respect that. The zero time means no deadline.
+		if err := c.conn.SetDeadline(time.Time{}); err != nil {
+			return nil, err
+		}
+	}
+
+	// Check if we are upgrading.
+	upgrading := c.upgrading
+
+	// Add handler before sending command, to be sure to get the response in time
+	// (in tests, the response is sent right after our command is received, so
+	// sometimes the response was received before the setup of this handler)
+	doneHandle := make(chan handleResult, 1)
+	unregister := make(chan struct{})
+	c.registerHandler(responses.HandlerFunc(func(resp imap.Resp) error {
+		select {
+		case <-unregister:
+			// If an error occured while sending the command, abort
+			return errUnregisterHandler
+		default:
+		}
+
+		if s, ok := resp.(*imap.StatusResp); ok && s.Tag == cmd.Tag {
+			// This is the command's status response, we're done
+			doneHandle <- handleResult{s, nil}
+			// Special handling of connection upgrading.
+			if upgrading {
+				c.upgrading = false
+				// Wait for upgrade to finish.
+				c.conn.Wait()
+			}
+			// Cancel any pending literal write
+			select {
+			case c.continues <- false:
+			default:
+			}
+			return errUnregisterHandler
+		}
+
+		if h != nil {
+			// Pass the response to the response handler
+			if err := h.Handle(resp); err != nil && err != responses.ErrUnhandled {
+				// If the response handler returns an error, abort
+				doneHandle <- handleResult{nil, err}
+				return errUnregisterHandler
+			} else {
+				return err
+			}
+		}
+		return responses.ErrUnhandled
+	}))
+
+	// Send the command to the server
+	if err := cmd.WriteTo(c.conn.Writer); err != nil {
+		// Error while sending the command
+		close(unregister)
+
+		if err, ok := err.(imap.LiteralLengthErr); ok {
+			// Expected > Actual
+			//  The server is waiting for us to write
+			//  more bytes, we don't have them. Run.
+			// Expected < Actual
+			//  We are about to send a potentially truncated message, we don't
+			//  want this (ths terminating CRLF is not sent at this point).
+			c.conn.Close()
+			return nil, err
+		}
+
+		return nil, err
+	}
+	// Flush writer if we are upgrading
+	if upgrading {
+		if err := c.conn.Writer.Flush(); err != nil {
+			// Error while sending the command
+			close(unregister)
+			return nil, err
+		}
+	}
+
+	for {
+		select {
+		case reply := <-replies:
+			// Response handler needs to send a reply (Used for AUTHENTICATE)
+			if err := c.writeReply(reply); err != nil {
+				close(unregister)
+				return nil, err
+			}
+		case <-c.loggedOut:
+			// If the connection is closed (such as from an I/O error), ensure we
+			// realize this and don't block waiting on a response that will never
+			// come. loggedOut is a channel that closes when the reader goroutine
+			// ends.
+			close(unregister)
+			return nil, errClosed
+		case result := <-doneHandle:
+			return result.status, result.err
+		}
+	}
+}
+
+// State returns the current connection state.
+func (c *Client) State() imap.ConnState {
+	c.locker.Lock()
+	state := c.state
+	c.locker.Unlock()
+	return state
+}
+
+// Mailbox returns the selected mailbox. It returns nil if there isn't one.
+func (c *Client) Mailbox() *imap.MailboxStatus {
+	// c.Mailbox fields are not supposed to change, so we can return the pointer.
+	c.locker.Lock()
+	mbox := c.mailbox
+	c.locker.Unlock()
+	return mbox
+}
+
+// SetState sets this connection's internal state.
+//
+// This function should not be called directly, it must only be used by
+// libraries implementing extensions of the IMAP protocol.
+func (c *Client) SetState(state imap.ConnState, mailbox *imap.MailboxStatus) {
+	c.locker.Lock()
+	c.state = state
+	c.mailbox = mailbox
+	c.locker.Unlock()
+}
+
+// Execute executes a generic command. cmdr is a value that can be converted to
+// a raw command and h is a response handler. The function returns when the
+// command has completed or failed, in this case err is nil. A non-nil err value
+// indicates a network error.
+//
+// This function should not be called directly, it must only be used by
+// libraries implementing extensions of the IMAP protocol.
+func (c *Client) Execute(cmdr imap.Commander, h responses.Handler) (*imap.StatusResp, error) {
+	return c.execute(cmdr, h)
+}
+
+func (c *Client) handleContinuationReqs() {
+	c.registerHandler(responses.HandlerFunc(func(resp imap.Resp) error {
+		if _, ok := resp.(*imap.ContinuationReq); ok {
+			go func() {
+				c.continues <- true
+			}()
+			return nil
+		}
+		return responses.ErrUnhandled
+	}))
+}
+
+func (c *Client) gotStatusCaps(args []interface{}) {
+	c.locker.Lock()
+
+	c.caps = make(map[string]bool)
+	for _, cap := range args {
+		if cap, ok := cap.(string); ok {
+			c.caps[cap] = true
+		}
+	}
+
+	c.locker.Unlock()
+}
+
+// The server can send unilateral data. This function handles it.
+func (c *Client) handleUnilateral() {
+	c.registerHandler(responses.HandlerFunc(func(resp imap.Resp) error {
+		switch resp := resp.(type) {
+		case *imap.StatusResp:
+			if resp.Tag != "*" {
+				return responses.ErrUnhandled
+			}
+
+			switch resp.Type {
+			case imap.StatusRespOk, imap.StatusRespNo, imap.StatusRespBad:
+				if c.Updates != nil {
+					c.Updates <- &StatusUpdate{resp}
+				}
+			case imap.StatusRespBye:
+				c.locker.Lock()
+				c.state = imap.LogoutState
+				c.mailbox = nil
+				c.locker.Unlock()
+
+				c.conn.Close()
+
+				if c.Updates != nil {
+					c.Updates <- &StatusUpdate{resp}
+				}
+			default:
+				return responses.ErrUnhandled
+			}
+		case *imap.DataResp:
+			name, fields, ok := imap.ParseNamedResp(resp)
+			if !ok {
+				return responses.ErrUnhandled
+			}
+
+			switch name {
+			case "CAPABILITY":
+				c.gotStatusCaps(fields)
+			case "EXISTS":
+				if c.Mailbox() == nil {
+					break
+				}
+
+				if messages, err := imap.ParseNumber(fields[0]); err == nil {
+					c.locker.Lock()
+					c.mailbox.Messages = messages
+					c.locker.Unlock()
+
+					c.mailbox.ItemsLocker.Lock()
+					c.mailbox.Items[imap.StatusMessages] = nil
+					c.mailbox.ItemsLocker.Unlock()
+				}
+
+				if c.Updates != nil {
+					c.Updates <- &MailboxUpdate{c.Mailbox()}
+				}
+			case "RECENT":
+				if c.Mailbox() == nil {
+					break
+				}
+
+				if recent, err := imap.ParseNumber(fields[0]); err == nil {
+					c.locker.Lock()
+					c.mailbox.Recent = recent
+					c.locker.Unlock()
+
+					c.mailbox.ItemsLocker.Lock()
+					c.mailbox.Items[imap.StatusRecent] = nil
+					c.mailbox.ItemsLocker.Unlock()
+				}
+
+				if c.Updates != nil {
+					c.Updates <- &MailboxUpdate{c.Mailbox()}
+				}
+			case "EXPUNGE":
+				seqNum, _ := imap.ParseNumber(fields[0])
+
+				if c.Updates != nil {
+					c.Updates <- &ExpungeUpdate{seqNum}
+				}
+			case "FETCH":
+				seqNum, _ := imap.ParseNumber(fields[0])
+				fields, _ := fields[1].([]interface{})
+
+				msg := &imap.Message{SeqNum: seqNum}
+				if err := msg.Parse(fields); err != nil {
+					break
+				}
+
+				if c.Updates != nil {
+					c.Updates <- &MessageUpdate{msg}
+				}
+			default:
+				return responses.ErrUnhandled
+			}
+		default:
+			return responses.ErrUnhandled
+		}
+		return nil
+	}))
+}
+
+func (c *Client) handleGreetAndStartReading() error {
+	var greetErr error
+	gotGreet := false
+
+	c.registerHandler(responses.HandlerFunc(func(resp imap.Resp) error {
+		status, ok := resp.(*imap.StatusResp)
+		if !ok {
+			greetErr = fmt.Errorf("invalid greeting received from server: not a status response")
+			return errUnregisterHandler
+		}
+
+		c.locker.Lock()
+		switch status.Type {
+		case imap.StatusRespPreauth:
+			c.state = imap.AuthenticatedState
+		case imap.StatusRespBye:
+			c.state = imap.LogoutState
+		case imap.StatusRespOk:
+			c.state = imap.NotAuthenticatedState
+		default:
+			c.state = imap.LogoutState
+			c.locker.Unlock()
+			greetErr = fmt.Errorf("invalid greeting received from server: %v", status.Type)
+			return errUnregisterHandler
+		}
+		c.locker.Unlock()
+
+		if status.Code == imap.CodeCapability {
+			c.gotStatusCaps(status.Arguments)
+		}
+
+		gotGreet = true
+		return errUnregisterHandler
+	}))
+
+	// call `readOnce` until we get the greeting or an error
+	for !gotGreet {
+		connected, err := c.readOnce()
+		// Check for read errors
+		if err != nil {
+			// return read errors
+			return err
+		}
+		// Check for invalid greet
+		if greetErr != nil {
+			// return read errors
+			return greetErr
+		}
+		// Check if connection was closed.
+		if !connected {
+			// connection closed.
+			return io.EOF
+		}
+	}
+
+	// We got the greeting, now start the reader goroutine.
+	go c.reader()
+
+	return nil
+}
+
+// Upgrade a connection, e.g. wrap an unencrypted connection with an encrypted
+// tunnel.
+//
+// This function should not be called directly, it must only be used by
+// libraries implementing extensions of the IMAP protocol.
+func (c *Client) Upgrade(upgrader imap.ConnUpgrader) error {
+	return c.conn.Upgrade(upgrader)
+}
+
+// Writer returns the imap.Writer for this client's connection.
+//
+// This function should not be called directly, it must only be used by
+// libraries implementing extensions of the IMAP protocol.
+func (c *Client) Writer() *imap.Writer {
+	return c.conn.Writer
+}
+
+// IsTLS checks if this client's connection has TLS enabled.
+func (c *Client) IsTLS() bool {
+	return c.isTLS
+}
+
+// LoggedOut returns a channel which is closed when the connection to the server
+// is closed.
+func (c *Client) LoggedOut() <-chan struct{} {
+	return c.loggedOut
+}
+
+// SetDebug defines an io.Writer to which all network activity will be logged.
+// If nil is provided, network activity will not be logged.
+func (c *Client) SetDebug(w io.Writer) {
+	// Need to send a command to unblock the reader goroutine.
+	cmd := new(commands.Noop)
+	err := c.Upgrade(func(conn net.Conn) (net.Conn, error) {
+		// Flag connection as in upgrading
+		c.upgrading = true
+		if status, err := c.execute(cmd, nil); err != nil {
+			return nil, err
+		} else if err := status.Err(); err != nil {
+			return nil, err
+		}
+
+		// Wait for reader to block.
+		c.conn.WaitReady()
+
+		c.conn.SetDebug(w)
+		return conn, nil
+	})
+	if err != nil {
+		log.Println("SetDebug:", err)
+	}
+
+}
+
+// New creates a new client from an existing connection.
+func New(conn net.Conn) (*Client, error) {
+	continues := make(chan bool)
+	w := imap.NewClientWriter(nil, continues)
+	r := imap.NewReader(nil)
+
+	c := &Client{
+		conn:      imap.NewConn(conn, r, w),
+		loggedOut: make(chan struct{}),
+		continues: continues,
+		state:     imap.ConnectingState,
+		ErrorLog:  log.New(os.Stderr, "imap/client: ", log.LstdFlags),
+	}
+
+	c.handleContinuationReqs()
+	c.handleUnilateral()
+	if err := c.handleGreetAndStartReading(); err != nil {
+		return c, err
+	}
+
+	plusOk, _ := c.Support("LITERAL+")
+	minusOk, _ := c.Support("LITERAL-")
+	// We don't use non-sync literal if it is bigger than 4096 bytes, so
+	// LITERAL- is fine too.
+	c.conn.AllowAsyncLiterals = plusOk || minusOk
+
+	return c, nil
+}
+
+// Dial connects to an IMAP server using an unencrypted connection.
+func Dial(addr string) (*Client, error) {
+	return DialWithDialer(new(net.Dialer), addr)
+}
+
+type Dialer interface {
+	// Dial connects to the given address.
+	Dial(network, addr string) (net.Conn, error)
+}
+
+// DialWithDialer connects to an IMAP server using an unencrypted connection
+// using dialer.Dial.
+//
+// Among other uses, this allows to apply a dial timeout.
+func DialWithDialer(dialer Dialer, addr string) (*Client, error) {
+	conn, err := dialer.Dial("tcp", addr)
+	if err != nil {
+		return nil, err
+	}
+
+	// We don't return to the caller until we try to receive a greeting. As such,
+	// there is no way to set the client's Timeout for that action. As a
+	// workaround, if the dialer has a timeout set, use that for the connection's
+	// deadline.
+	if netDialer, ok := dialer.(*net.Dialer); ok && netDialer.Timeout > 0 {
+		err := conn.SetDeadline(time.Now().Add(netDialer.Timeout))
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	c, err := New(conn)
+	if err != nil {
+		return nil, err
+	}
+
+	c.serverName, _, _ = net.SplitHostPort(addr)
+	return c, nil
+}
+
+// DialTLS connects to an IMAP server using an encrypted connection.
+func DialTLS(addr string, tlsConfig *tls.Config) (*Client, error) {
+	return DialWithDialerTLS(new(net.Dialer), addr, tlsConfig)
+}
+
+// DialWithDialerTLS connects to an IMAP server using an encrypted connection
+// using dialer.Dial.
+//
+// Among other uses, this allows to apply a dial timeout.
+func DialWithDialerTLS(dialer Dialer, addr string, tlsConfig *tls.Config) (*Client, error) {
+	conn, err := dialer.Dial("tcp", addr)
+	if err != nil {
+		return nil, err
+	}
+
+	serverName, _, _ := net.SplitHostPort(addr)
+	if tlsConfig == nil {
+		tlsConfig = &tls.Config{}
+	}
+	if tlsConfig.ServerName == "" {
+		tlsConfig = tlsConfig.Clone()
+		tlsConfig.ServerName = serverName
+	}
+	tlsConn := tls.Client(conn, tlsConfig)
+
+	// We don't return to the caller until we try to receive a greeting. As such,
+	// there is no way to set the client's Timeout for that action. As a
+	// workaround, if the dialer has a timeout set, use that for the connection's
+	// deadline.
+	if netDialer, ok := dialer.(*net.Dialer); ok && netDialer.Timeout > 0 {
+		err := tlsConn.SetDeadline(time.Now().Add(netDialer.Timeout))
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	c, err := New(tlsConn)
+	if err != nil {
+		return nil, err
+	}
+
+	c.isTLS = true
+	c.serverName = serverName
+	return c, nil
+}

client/client_test.go

@@ -0,0 +1,187 @@
+package client
+
+import (
+	"bufio"
+	"bytes"
+	"io"
+	"net"
+	"strings"
+	"testing"
+
+	"github.com/emersion/go-imap"
+)
+
+type cmdScanner struct {
+	scanner *bufio.Scanner
+}
+
+func (s *cmdScanner) ScanLine() string {
+	s.scanner.Scan()
+	return s.scanner.Text()
+}
+
+func (s *cmdScanner) ScanCmd() (tag string, cmd string) {
+	parts := strings.SplitN(s.ScanLine(), " ", 2)
+	return parts[0], parts[1]
+}
+
+func newCmdScanner(r io.Reader) *cmdScanner {
+	return &cmdScanner{
+		scanner: bufio.NewScanner(r),
+	}
+}
+
+type serverConn struct {
+	*cmdScanner
+	net.Conn
+	net.Listener
+}
+
+func (c *serverConn) Close() error {
+	if err := c.Conn.Close(); err != nil {
+		return err
+	}
+	return c.Listener.Close()
+}
+
+func (c *serverConn) WriteString(s string) (n int, err error) {
+	return io.WriteString(c.Conn, s)
+}
+
+func newTestClient(t *testing.T) (c *Client, s *serverConn) {
+	return newTestClientWithGreeting(t, "* OK [CAPABILITY IMAP4rev1 STARTTLS AUTH=PLAIN UNSELECT] Server ready.\r\n")
+}
+
+func newTestClientWithGreeting(t *testing.T, greeting string) (c *Client, s *serverConn) {
+	l, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	done := make(chan struct{})
+	go func() {
+		conn, err := l.Accept()
+		if err != nil {
+			panic(err)
+		}
+
+		if _, err := io.WriteString(conn, greeting); err != nil {
+			panic(err)
+		}
+
+		s = &serverConn{newCmdScanner(conn), conn, l}
+		close(done)
+	}()
+
+	c, err = Dial(l.Addr().String())
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	<-done
+	return
+}
+
+func setClientState(c *Client, state imap.ConnState, mailbox *imap.MailboxStatus) {
+	c.locker.Lock()
+	c.state = state
+	c.mailbox = mailbox
+	c.locker.Unlock()
+}
+
+func TestClient(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	if ok, err := c.Support("IMAP4rev1"); err != nil {
+		t.Fatal("c.Support(IMAP4rev1) =", err)
+	} else if !ok {
+		t.Fatal("c.Support(IMAP4rev1) = false, want true")
+	}
+}
+
+func TestClient_SetDebug(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	var b bytes.Buffer
+	done := make(chan error)
+
+	go func() {
+		c.SetDebug(&b)
+		done <- nil
+	}()
+	if tag, cmd := s.ScanCmd(); cmd != "NOOP" {
+		t.Fatal("Bad command:", cmd)
+	} else {
+		s.WriteString(tag + " OK NOOP completed.\r\n")
+	}
+	// wait for SetDebug to finish.
+	<-done
+
+	go func() {
+		_, err := c.Capability()
+		done <- err
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "CAPABILITY" {
+		t.Fatal("Bad command:", cmd)
+	}
+
+	s.WriteString("* CAPABILITY IMAP4rev1\r\n")
+	s.WriteString(tag + " OK CAPABILITY completed.\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatal("c.Capability() =", err)
+	}
+
+	if b.Len() == 0 {
+		t.Error("empty debug buffer")
+	}
+}
+
+func TestClient_unilateral(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, imap.NewMailboxStatus("INBOX", nil))
+
+	updates := make(chan Update, 1)
+	c.Updates = updates
+
+	s.WriteString("* 42 EXISTS\r\n")
+	if update, ok := (<-updates).(*MailboxUpdate); !ok || update.Mailbox.Messages != 42 {
+		t.Errorf("Invalid messages count: expected %v but got %v", 42, update.Mailbox.Messages)
+	}
+
+	s.WriteString("* 587 RECENT\r\n")
+	if update, ok := (<-updates).(*MailboxUpdate); !ok || update.Mailbox.Recent != 587 {
+		t.Errorf("Invalid recent count: expected %v but got %v", 587, update.Mailbox.Recent)
+	}
+
+	s.WriteString("* 65535 EXPUNGE\r\n")
+	if update, ok := (<-updates).(*ExpungeUpdate); !ok || update.SeqNum != 65535 {
+		t.Errorf("Invalid expunged sequence number: expected %v but got %v", 65535, update.SeqNum)
+	}
+
+	s.WriteString("* 431 FETCH (FLAGS (\\Seen))\r\n")
+	if update, ok := (<-updates).(*MessageUpdate); !ok || update.Message.SeqNum != 431 {
+		t.Errorf("Invalid expunged sequence number: expected %v but got %v", 431, update.Message.SeqNum)
+	}
+
+	s.WriteString("* OK Reticulating splines...\r\n")
+	if update, ok := (<-updates).(*StatusUpdate); !ok || update.Status.Info != "Reticulating splines..." {
+		t.Errorf("Invalid info: got %v", update.Status.Info)
+	}
+
+	s.WriteString("* NO Kansai band competition is in 30 seconds !\r\n")
+	if update, ok := (<-updates).(*StatusUpdate); !ok || update.Status.Info != "Kansai band competition is in 30 seconds !" {
+		t.Errorf("Invalid warning: got %v", update.Status.Info)
+	}
+
+	s.WriteString("* BAD Battery level too low, shutting down.\r\n")
+	if update, ok := (<-updates).(*StatusUpdate); !ok || update.Status.Info != "Battery level too low, shutting down." {
+		t.Errorf("Invalid error: got %v", update.Status.Info)
+	}
+}

client/cmd_any.go

@@ -0,0 +1,88 @@
+package client
+
+import (
+	"errors"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/commands"
+)
+
+// ErrAlreadyLoggedOut is returned if Logout is called when the client is
+// already logged out.
+var ErrAlreadyLoggedOut = errors.New("Already logged out")
+
+// Capability requests a listing of capabilities that the server supports.
+// Capabilities are often returned by the server with the greeting or with the
+// STARTTLS and LOGIN responses, so usually explicitly requesting capabilities
+// isn't needed.
+//
+// Most of the time, Support should be used instead.
+func (c *Client) Capability() (map[string]bool, error) {
+	cmd := &commands.Capability{}
+
+	if status, err := c.execute(cmd, nil); err != nil {
+		return nil, err
+	} else if err := status.Err(); err != nil {
+		return nil, err
+	}
+
+	c.locker.Lock()
+	caps := c.caps
+	c.locker.Unlock()
+	return caps, nil
+}
+
+// Support checks if cap is a capability supported by the server. If the server
+// hasn't sent its capabilities yet, Support requests them.
+func (c *Client) Support(cap string) (bool, error) {
+	c.locker.Lock()
+	ok := c.caps != nil
+	c.locker.Unlock()
+
+	// If capabilities are not cached, request them
+	if !ok {
+		if _, err := c.Capability(); err != nil {
+			return false, err
+		}
+	}
+
+	c.locker.Lock()
+	supported := c.caps[cap]
+	c.locker.Unlock()
+
+	return supported, nil
+}
+
+// Noop always succeeds and does nothing.
+//
+// It can be used as a periodic poll for new messages or message status updates
+// during a period of inactivity. It can also be used to reset any inactivity
+// autologout timer on the server.
+func (c *Client) Noop() error {
+	cmd := new(commands.Noop)
+
+	status, err := c.execute(cmd, nil)
+	if err != nil {
+		return err
+	}
+	return status.Err()
+}
+
+// Logout gracefully closes the connection.
+func (c *Client) Logout() error {
+	if c.State() == imap.LogoutState {
+		return ErrAlreadyLoggedOut
+	}
+
+	cmd := new(commands.Logout)
+
+	if status, err := c.execute(cmd, nil); err == errClosed {
+		// Server closed connection, that's what we want anyway
+		return nil
+	} else if err != nil {
+		return err
+	} else if status != nil {
+		return status.Err()
+	}
+	return nil
+}

client/cmd_any_test.go

@@ -0,0 +1,80 @@
+package client
+
+import (
+	"testing"
+
+	"github.com/emersion/go-imap"
+)
+
+func TestClient_Capability(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	var caps map[string]bool
+	done := make(chan error, 1)
+	go func() {
+		var err error
+		caps, err = c.Capability()
+		done <- err
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "CAPABILITY" {
+		t.Fatalf("client sent command %v, want CAPABILITY", cmd)
+	}
+	s.WriteString("* CAPABILITY IMAP4rev1 XTEST\r\n")
+	s.WriteString(tag + " OK CAPABILITY completed.\r\n")
+
+	if err := <-done; err != nil {
+		t.Error("c.Capability() = ", err)
+	}
+
+	if !caps["XTEST"] {
+		t.Error("XTEST capability missing")
+	}
+}
+
+func TestClient_Noop(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Noop()
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "NOOP" {
+		t.Fatalf("client sent command %v, want NOOP", cmd)
+	}
+	s.WriteString(tag + " OK NOOP completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Error("c.Noop() = ", err)
+	}
+}
+
+func TestClient_Logout(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Logout()
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "LOGOUT" {
+		t.Fatalf("client sent command %v, want LOGOUT", cmd)
+	}
+	s.WriteString("* BYE Client asked to close the connection.\r\n")
+	s.WriteString(tag + " OK LOGOUT completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Error("c.Logout() =", err)
+	}
+
+	if state := c.State(); state != imap.LogoutState {
+		t.Errorf("c.State() = %v, want %v", state, imap.LogoutState)
+	}
+}

client/cmd_auth.go

@@ -0,0 +1,380 @@
+package client
+
+import (
+	"errors"
+	"time"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/commands"
+	"github.com/emersion/go-imap/responses"
+)
+
+// ErrNotLoggedIn is returned if a function that requires the client to be
+// logged in is called then the client isn't.
+var ErrNotLoggedIn = errors.New("Not logged in")
+
+func (c *Client) ensureAuthenticated() error {
+	state := c.State()
+	if state != imap.AuthenticatedState && state != imap.SelectedState {
+		return ErrNotLoggedIn
+	}
+	return nil
+}
+
+// Select selects a mailbox so that messages in the mailbox can be accessed. Any
+// currently selected mailbox is deselected before attempting the new selection.
+// Even if the readOnly parameter is set to false, the server can decide to open
+// the mailbox in read-only mode.
+func (c *Client) Select(name string, readOnly bool) (*imap.MailboxStatus, error) {
+	if err := c.ensureAuthenticated(); err != nil {
+		return nil, err
+	}
+
+	cmd := &commands.Select{
+		Mailbox:  name,
+		ReadOnly: readOnly,
+	}
+
+	mbox := &imap.MailboxStatus{Name: name, Items: make(map[imap.StatusItem]interface{})}
+	res := &responses.Select{
+		Mailbox: mbox,
+	}
+	c.locker.Lock()
+	c.mailbox = mbox
+	c.locker.Unlock()
+
+	status, err := c.execute(cmd, res)
+	if err != nil {
+		c.locker.Lock()
+		c.mailbox = nil
+		c.locker.Unlock()
+		return nil, err
+	}
+	if err := status.Err(); err != nil {
+		c.locker.Lock()
+		c.mailbox = nil
+		c.locker.Unlock()
+		return nil, err
+	}
+
+	c.locker.Lock()
+	mbox.ReadOnly = (status.Code == imap.CodeReadOnly)
+	c.state = imap.SelectedState
+	c.locker.Unlock()
+	return mbox, nil
+}
+
+// Create creates a mailbox with the given name.
+func (c *Client) Create(name string) error {
+	if err := c.ensureAuthenticated(); err != nil {
+		return err
+	}
+
+	cmd := &commands.Create{
+		Mailbox: name,
+	}
+
+	status, err := c.execute(cmd, nil)
+	if err != nil {
+		return err
+	}
+	return status.Err()
+}
+
+// Delete permanently removes the mailbox with the given name.
+func (c *Client) Delete(name string) error {
+	if err := c.ensureAuthenticated(); err != nil {
+		return err
+	}
+
+	cmd := &commands.Delete{
+		Mailbox: name,
+	}
+
+	status, err := c.execute(cmd, nil)
+	if err != nil {
+		return err
+	}
+	return status.Err()
+}
+
+// Rename changes the name of a mailbox.
+func (c *Client) Rename(existingName, newName string) error {
+	if err := c.ensureAuthenticated(); err != nil {
+		return err
+	}
+
+	cmd := &commands.Rename{
+		Existing: existingName,
+		New:      newName,
+	}
+
+	status, err := c.execute(cmd, nil)
+	if err != nil {
+		return err
+	}
+	return status.Err()
+}
+
+// Subscribe adds the specified mailbox name to the server's set of "active" or
+// "subscribed" mailboxes.
+func (c *Client) Subscribe(name string) error {
+	if err := c.ensureAuthenticated(); err != nil {
+		return err
+	}
+
+	cmd := &commands.Subscribe{
+		Mailbox: name,
+	}
+
+	status, err := c.execute(cmd, nil)
+	if err != nil {
+		return err
+	}
+	return status.Err()
+}
+
+// Unsubscribe removes the specified mailbox name from the server's set of
+// "active" or "subscribed" mailboxes.
+func (c *Client) Unsubscribe(name string) error {
+	if err := c.ensureAuthenticated(); err != nil {
+		return err
+	}
+
+	cmd := &commands.Unsubscribe{
+		Mailbox: name,
+	}
+
+	status, err := c.execute(cmd, nil)
+	if err != nil {
+		return err
+	}
+	return status.Err()
+}
+
+// List returns a subset of names from the complete set of all names available
+// to the client.
+//
+// An empty name argument is a special request to return the hierarchy delimiter
+// and the root name of the name given in the reference. The character "*" is a
+// wildcard, and matches zero or more characters at this position. The
+// character "%" is similar to "*", but it does not match a hierarchy delimiter.
+func (c *Client) List(ref, name string, ch chan *imap.MailboxInfo) error {
+	defer close(ch)
+
+	if err := c.ensureAuthenticated(); err != nil {
+		return err
+	}
+
+	cmd := &commands.List{
+		Reference: ref,
+		Mailbox:   name,
+	}
+	res := &responses.List{Mailboxes: ch}
+
+	status, err := c.execute(cmd, res)
+	if err != nil {
+		return err
+	}
+	return status.Err()
+}
+
+// Lsub returns a subset of names from the set of names that the user has
+// declared as being "active" or "subscribed".
+func (c *Client) Lsub(ref, name string, ch chan *imap.MailboxInfo) error {
+	defer close(ch)
+
+	if err := c.ensureAuthenticated(); err != nil {
+		return err
+	}
+
+	cmd := &commands.List{
+		Reference:  ref,
+		Mailbox:    name,
+		Subscribed: true,
+	}
+	res := &responses.List{
+		Mailboxes:  ch,
+		Subscribed: true,
+	}
+
+	status, err := c.execute(cmd, res)
+	if err != nil {
+		return err
+	}
+	return status.Err()
+}
+
+// Status requests the status of the indicated mailbox. It does not change the
+// currently selected mailbox, nor does it affect the state of any messages in
+// the queried mailbox.
+//
+// See RFC 3501 section 6.3.10 for a list of items that can be requested.
+func (c *Client) Status(name string, items []imap.StatusItem) (*imap.MailboxStatus, error) {
+	if err := c.ensureAuthenticated(); err != nil {
+		return nil, err
+	}
+
+	cmd := &commands.Status{
+		Mailbox: name,
+		Items:   items,
+	}
+	res := &responses.Status{
+		Mailbox: new(imap.MailboxStatus),
+	}
+
+	status, err := c.execute(cmd, res)
+	if err != nil {
+		return nil, err
+	}
+	return res.Mailbox, status.Err()
+}
+
+// Append appends the literal argument as a new message to the end of the
+// specified destination mailbox. This argument SHOULD be in the format of an
+// RFC 2822 message. flags and date are optional arguments and can be set to
+// nil and the empty struct.
+func (c *Client) Append(mbox string, flags []string, date time.Time, msg imap.Literal) error {
+	if err := c.ensureAuthenticated(); err != nil {
+		return err
+	}
+
+	cmd := &commands.Append{
+		Mailbox: mbox,
+		Flags:   flags,
+		Date:    date,
+		Message: msg,
+	}
+
+	status, err := c.execute(cmd, nil)
+	if err != nil {
+		return err
+	}
+	return status.Err()
+}
+
+// Enable requests the server to enable the named extensions. The extensions
+// which were successfully enabled are returned.
+//
+// See RFC 5161 section 3.1.
+func (c *Client) Enable(caps []string) ([]string, error) {
+	if ok, err := c.Support("ENABLE"); !ok || err != nil {
+		return nil, ErrExtensionUnsupported
+	}
+
+	// ENABLE is invalid if a mailbox has been selected.
+	if c.State() != imap.AuthenticatedState {
+		return nil, ErrNotLoggedIn
+	}
+
+	cmd := &commands.Enable{Caps: caps}
+	res := &responses.Enabled{}
+
+	if status, err := c.Execute(cmd, res); err != nil {
+		return nil, err
+	} else {
+		return res.Caps, status.Err()
+	}
+}
+
+func (c *Client) idle(stop <-chan struct{}) error {
+	cmd := &commands.Idle{}
+
+	res := &responses.Idle{
+		Stop:      stop,
+		RepliesCh: make(chan []byte, 10),
+	}
+
+	if status, err := c.Execute(cmd, res); err != nil {
+		return err
+	} else {
+		return status.Err()
+	}
+}
+
+// IdleOptions holds options for Client.Idle.
+type IdleOptions struct {
+	// LogoutTimeout is used to avoid being logged out by the server when
+	// idling. Each LogoutTimeout, the IDLE command is restarted. If set to
+	// zero, a default is used. If negative, this behavior is disabled.
+	LogoutTimeout time.Duration
+	// Poll interval when the server doesn't support IDLE. If zero, a default
+	// is used. If negative, polling is always disabled.
+	PollInterval time.Duration
+}
+
+// Idle indicates to the server that the client is ready to receive unsolicited
+// mailbox update messages. When the client wants to send commands again, it
+// must first close stop.
+//
+// If the server doesn't support IDLE, go-imap falls back to polling.
+func (c *Client) Idle(stop <-chan struct{}, opts *IdleOptions) error {
+	if ok, err := c.Support("IDLE"); err != nil {
+		return err
+	} else if !ok {
+		return c.idleFallback(stop, opts)
+	}
+
+	logoutTimeout := 25 * time.Minute
+	if opts != nil {
+		if opts.LogoutTimeout > 0 {
+			logoutTimeout = opts.LogoutTimeout
+		} else if opts.LogoutTimeout < 0 {
+			return c.idle(stop)
+		}
+	}
+
+	t := time.NewTicker(logoutTimeout)
+	defer t.Stop()
+
+	for {
+		stopOrRestart := make(chan struct{})
+		done := make(chan error, 1)
+		go func() {
+			done <- c.idle(stopOrRestart)
+		}()
+
+		select {
+		case <-t.C:
+			close(stopOrRestart)
+			if err := <-done; err != nil {
+				return err
+			}
+		case <-stop:
+			close(stopOrRestart)
+			return <-done
+		case err := <-done:
+			close(stopOrRestart)
+			if err != nil {
+				return err
+			}
+		}
+	}
+}
+
+func (c *Client) idleFallback(stop <-chan struct{}, opts *IdleOptions) error {
+	pollInterval := time.Minute
+	if opts != nil {
+		if opts.PollInterval > 0 {
+			pollInterval = opts.PollInterval
+		} else if opts.PollInterval < 0 {
+			return ErrExtensionUnsupported
+		}
+	}
+
+	t := time.NewTicker(pollInterval)
+	defer t.Stop()
+
+	for {
+		select {
+		case <-t.C:
+			if err := c.Noop(); err != nil {
+				return err
+			}
+		case <-stop:
+			return nil
+		case <-c.LoggedOut():
+			return errors.New("disconnected while idling")
+		}
+	}
+}

client/cmd_auth_test.go

@@ -0,0 +1,499 @@
+package client
+
+import (
+	"bytes"
+	"io"
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/emersion/go-imap"
+)
+
+func TestClient_Select(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.AuthenticatedState, nil)
+
+	var mbox *imap.MailboxStatus
+	done := make(chan error, 1)
+	go func() {
+		var err error
+		mbox, err = c.Select("INBOX", false)
+		done <- err
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "SELECT INBOX" {
+		t.Fatalf("client sent command %v, want SELECT \"INBOX\"", cmd)
+	}
+
+	s.WriteString("* 172 EXISTS\r\n")
+	s.WriteString("* 1 RECENT\r\n")
+	s.WriteString("* OK [UNSEEN 12] Message 12 is first unseen\r\n")
+	s.WriteString("* OK [UIDVALIDITY 3857529045] UIDs valid\r\n")
+	s.WriteString("* OK [UIDNEXT 4392] Predicted next UID\r\n")
+	s.WriteString("* FLAGS (\\Answered \\Flagged \\Deleted \\Seen \\Draft)\r\n")
+	s.WriteString("* OK [PERMANENTFLAGS (\\Deleted \\Seen \\*)] Limited\r\n")
+	s.WriteString(tag + " OK SELECT completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Select() = %v", err)
+	}
+
+	want := &imap.MailboxStatus{
+		Name:           "INBOX",
+		ReadOnly:       false,
+		Flags:          []string{imap.AnsweredFlag, imap.FlaggedFlag, imap.DeletedFlag, imap.SeenFlag, imap.DraftFlag},
+		PermanentFlags: []string{imap.DeletedFlag, imap.SeenFlag, "\\*"},
+		UnseenSeqNum:   12,
+		Messages:       172,
+		Recent:         1,
+		UidNext:        4392,
+		UidValidity:    3857529045,
+	}
+	mbox.Items = nil
+	if !reflect.DeepEqual(mbox, want) {
+		t.Errorf("c.Select() = \n%+v\n want \n%+v", mbox, want)
+	}
+}
+
+func TestClient_Select_ReadOnly(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.AuthenticatedState, nil)
+
+	var mbox *imap.MailboxStatus
+	done := make(chan error, 1)
+	go func() {
+		var err error
+		mbox, err = c.Select("INBOX", true)
+		done <- err
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "EXAMINE INBOX" {
+		t.Fatalf("client sent command %v, want EXAMINE \"INBOX\"", cmd)
+	}
+
+	s.WriteString(tag + " OK [READ-ONLY] EXAMINE completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Select() = %v", err)
+	}
+
+	if !mbox.ReadOnly {
+		t.Errorf("c.Select().ReadOnly = false, want true")
+	}
+}
+
+func TestClient_Create(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.AuthenticatedState, nil)
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Create("New Mailbox")
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "CREATE \"New Mailbox\"" {
+		t.Fatalf("client sent command %v, want %v", cmd, "CREATE \"New Mailbox\"")
+	}
+
+	s.WriteString(tag + " OK CREATE completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Create() = %v", err)
+	}
+}
+
+func TestClient_Delete(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.AuthenticatedState, nil)
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Delete("Old Mailbox")
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "DELETE \"Old Mailbox\"" {
+		t.Fatalf("client sent command %v, want %v", cmd, "DELETE \"Old Mailbox\"")
+	}
+
+	s.WriteString(tag + " OK DELETE completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Delete() = %v", err)
+	}
+}
+
+func TestClient_Rename(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.AuthenticatedState, nil)
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Rename("Old Mailbox", "New Mailbox")
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "RENAME \"Old Mailbox\" \"New Mailbox\"" {
+		t.Fatalf("client sent command %v, want %v", cmd, "RENAME \"Old Mailbox\" \"New Mailbox\"")
+	}
+
+	s.WriteString(tag + " OK RENAME completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Rename() = %v", err)
+	}
+}
+
+func TestClient_Subscribe(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.AuthenticatedState, nil)
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Subscribe("Mailbox")
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "SUBSCRIBE \"Mailbox\"" {
+		t.Fatalf("client sent command %v, want %v", cmd, "SUBSCRIBE \"Mailbox\"")
+	}
+
+	s.WriteString(tag + " OK SUBSCRIBE completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Subscribe() = %v", err)
+	}
+}
+
+func TestClient_Unsubscribe(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.AuthenticatedState, nil)
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Unsubscribe("Mailbox")
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "UNSUBSCRIBE \"Mailbox\"" {
+		t.Fatalf("client sent command %v, want %v", cmd, "UNSUBSCRIBE \"Mailbox\"")
+	}
+
+	s.WriteString(tag + " OK UNSUBSCRIBE completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Unsubscribe() = %v", err)
+	}
+}
+
+func TestClient_List(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.AuthenticatedState, nil)
+
+	done := make(chan error, 1)
+	mailboxes := make(chan *imap.MailboxInfo, 3)
+	go func() {
+		done <- c.List("", "%", mailboxes)
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "LIST \"\" \"%\"" {
+		t.Fatalf("client sent command %v, want %v", cmd, "LIST \"\" \"%\"")
+	}
+
+	s.WriteString("* LIST (flag1) \"/\" INBOX\r\n")
+	s.WriteString("* LIST (flag2 flag3) \"/\" Drafts\r\n")
+	s.WriteString("* LIST () \"/\" Sent\r\n")
+	s.WriteString(tag + " OK LIST completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.List() = %v", err)
+	}
+
+	want := []struct {
+		name       string
+		attributes []string
+	}{
+		{"INBOX", []string{"flag1"}},
+		{"Drafts", []string{"flag2", "flag3"}},
+		{"Sent", []string{}},
+	}
+
+	i := 0
+	for mbox := range mailboxes {
+		if mbox.Name != want[i].name {
+			t.Errorf("Bad mailbox name for %v: %v, want %v", i, mbox.Name, want[i].name)
+		}
+
+		if !reflect.DeepEqual(mbox.Attributes, want[i].attributes) {
+			t.Errorf("Bad mailbox attributes for %v: %v, want %v", i, mbox.Attributes, want[i].attributes)
+		}
+
+		i++
+	}
+}
+
+func TestClient_Lsub(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.AuthenticatedState, nil)
+
+	done := make(chan error, 1)
+	mailboxes := make(chan *imap.MailboxInfo, 1)
+	go func() {
+		done <- c.Lsub("", "%", mailboxes)
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "LSUB \"\" \"%\"" {
+		t.Fatalf("client sent command %v, want %v", cmd, "LSUB \"\" \"%\"")
+	}
+
+	s.WriteString("* LSUB () \"/\" INBOX\r\n")
+	s.WriteString(tag + " OK LSUB completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Lsub() = %v", err)
+	}
+
+	mbox := <-mailboxes
+	if mbox.Name != "INBOX" {
+		t.Errorf("Bad mailbox name: %v", mbox.Name)
+	}
+	if len(mbox.Attributes) != 0 {
+		t.Errorf("Bad mailbox flags: %v", mbox.Attributes)
+	}
+}
+
+func TestClient_Status(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.AuthenticatedState, nil)
+
+	done := make(chan error, 1)
+	var mbox *imap.MailboxStatus
+	go func() {
+		var err error
+		mbox, err = c.Status("INBOX", []imap.StatusItem{imap.StatusMessages, imap.StatusRecent})
+		done <- err
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "STATUS INBOX (MESSAGES RECENT)" {
+		t.Fatalf("client sent command %v, want %v", cmd, "STATUS \"INBOX\" (MESSAGES RECENT)")
+	}
+
+	s.WriteString("* STATUS INBOX (MESSAGES 42 RECENT 1)\r\n")
+	s.WriteString(tag + " OK STATUS completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Status() = %v", err)
+	}
+
+	if mbox.Messages != 42 {
+		t.Errorf("Bad mailbox messages: %v", mbox.Messages)
+	}
+	if mbox.Recent != 1 {
+		t.Errorf("Bad mailbox recent: %v", mbox.Recent)
+	}
+}
+
+type literalWrap struct {
+	io.Reader
+	L int
+}
+
+func (lw literalWrap) Len() int {
+	return lw.L
+}
+
+func TestClient_Append_SmallerLiteral(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.AuthenticatedState, nil)
+
+	msg := "Hello World!\r\nHello Gophers!\r\n"
+	date := time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC)
+	flags := []string{imap.SeenFlag, imap.DraftFlag}
+
+	r := bytes.NewBufferString(msg)
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Append("INBOX", flags, date, literalWrap{r, 35})
+
+		// The buffer is not flushed on error, force it so io.ReadFull can
+		// continue.
+		c.conn.Flush()
+	}()
+
+	tag, _ := s.ScanCmd()
+	s.WriteString("+ send literal\r\n")
+
+	b := make([]byte, 30)
+	// The client will close connection.
+	if _, err := io.ReadFull(s, b); err != io.EOF {
+		t.Error("Expected EOF, got", err)
+	}
+
+	s.WriteString(tag + " OK APPEND completed\r\n")
+
+	err, ok := (<-done).(imap.LiteralLengthErr)
+	if !ok {
+		t.Fatalf("c.Append() = %v", err)
+	}
+	if err.Expected != 35 {
+		t.Fatalf("err.Expected = %v", err.Expected)
+	}
+	if err.Actual != 30 {
+		t.Fatalf("err.Actual = %v", err.Actual)
+	}
+}
+
+func TestClient_Append_BiggerLiteral(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.AuthenticatedState, nil)
+
+	msg := "Hello World!\r\nHello Gophers!\r\n"
+	date := time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC)
+	flags := []string{imap.SeenFlag, imap.DraftFlag}
+
+	r := bytes.NewBufferString(msg)
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Append("INBOX", flags, date, literalWrap{r, 25})
+
+		// The buffer is not flushed on error, force it so io.ReadFull can
+		// continue.
+		c.conn.Flush()
+	}()
+
+	tag, _ := s.ScanCmd()
+	s.WriteString("+ send literal\r\n")
+
+	// The client will close connection.
+	b := make([]byte, 25)
+	if _, err := io.ReadFull(s, b); err != io.EOF {
+		t.Error("Expected EOF, got", err)
+	}
+
+	s.WriteString(tag + " OK APPEND completed\r\n")
+
+	err, ok := (<-done).(imap.LiteralLengthErr)
+	if !ok {
+		t.Fatalf("c.Append() = %v", err)
+	}
+	if err.Expected != 25 {
+		t.Fatalf("err.Expected = %v", err.Expected)
+	}
+	if err.Actual != 30 {
+		t.Fatalf("err.Actual = %v", err.Actual)
+	}
+}
+
+func TestClient_Append(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.AuthenticatedState, nil)
+
+	msg := "Hello World!\r\nHello Gophers!\r\n"
+	date := time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC)
+	flags := []string{imap.SeenFlag, imap.DraftFlag}
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Append("INBOX", flags, date, bytes.NewBufferString(msg))
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "APPEND INBOX (\\Seen \\Draft) \"10-Nov-2009 23:00:00 +0000\" {30}" {
+		t.Fatalf("client sent command %v, want %v", cmd, "APPEND \"INBOX\" (\\Seen \\Draft) \"10-Nov-2009 23:00:00 +0000\" {30}")
+	}
+
+	s.WriteString("+ send literal\r\n")
+
+	b := make([]byte, 30)
+	if _, err := io.ReadFull(s, b); err != nil {
+		t.Fatal(err)
+	} else if string(b) != msg {
+		t.Fatal("Bad literal:", string(b))
+	}
+
+	s.WriteString(tag + " OK APPEND completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Append() = %v", err)
+	}
+}
+
+func TestClient_Append_failed(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.AuthenticatedState, nil)
+
+	// First the server refuses
+
+	msg := "First try"
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Append("INBOX", nil, time.Time{}, bytes.NewBufferString(msg))
+	}()
+
+	tag, _ := s.ScanCmd()
+	s.WriteString(tag + " BAD APPEND failed\r\n")
+
+	if err := <-done; err == nil {
+		t.Fatal("c.Append() = nil, want an error from the server")
+	}
+
+	// Try a second time, the server accepts
+
+	msg = "Second try"
+	go func() {
+		done <- c.Append("INBOX", nil, time.Time{}, bytes.NewBufferString(msg))
+	}()
+
+	tag, _ = s.ScanCmd()
+	s.WriteString("+ send literal\r\n")
+
+	b := make([]byte, len(msg))
+	if _, err := io.ReadFull(s, b); err != nil {
+		t.Fatal(err)
+	} else if string(b) != msg {
+		t.Fatal("Bad literal:", string(b))
+	}
+
+	s.WriteString(tag + " OK APPEND completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Append() = %v", err)
+	}
+}

client/cmd_noauth.go

@@ -0,0 +1,174 @@
+package client
+
+import (
+	"crypto/tls"
+	"errors"
+	"net"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/commands"
+	"github.com/emersion/go-imap/responses"
+	"github.com/emersion/go-sasl"
+)
+
+var (
+	// ErrAlreadyLoggedIn is returned if Login or Authenticate is called when the
+	// client is already logged in.
+	ErrAlreadyLoggedIn = errors.New("Already logged in")
+	// ErrTLSAlreadyEnabled is returned if StartTLS is called when TLS is already
+	// enabled.
+	ErrTLSAlreadyEnabled = errors.New("TLS is already enabled")
+	// ErrLoginDisabled is returned if Login or Authenticate is called when the
+	// server has disabled authentication. Most of the time, calling enabling TLS
+	// solves the problem.
+	ErrLoginDisabled = errors.New("Login is disabled in current state")
+)
+
+// SupportStartTLS checks if the server supports STARTTLS.
+func (c *Client) SupportStartTLS() (bool, error) {
+	return c.Support("STARTTLS")
+}
+
+// StartTLS starts TLS negotiation.
+func (c *Client) StartTLS(tlsConfig *tls.Config) error {
+	if c.isTLS {
+		return ErrTLSAlreadyEnabled
+	}
+
+	if tlsConfig == nil {
+		tlsConfig = new(tls.Config)
+	}
+	if tlsConfig.ServerName == "" {
+		tlsConfig = tlsConfig.Clone()
+		tlsConfig.ServerName = c.serverName
+	}
+
+	cmd := new(commands.StartTLS)
+
+	err := c.Upgrade(func(conn net.Conn) (net.Conn, error) {
+		// Flag connection as in upgrading
+		c.upgrading = true
+		if status, err := c.execute(cmd, nil); err != nil {
+			return nil, err
+		} else if err := status.Err(); err != nil {
+			return nil, err
+		}
+
+		// Wait for reader to block.
+		c.conn.WaitReady()
+		tlsConn := tls.Client(conn, tlsConfig)
+		if err := tlsConn.Handshake(); err != nil {
+			return nil, err
+		}
+
+		// Capabilities change when TLS is enabled
+		c.locker.Lock()
+		c.caps = nil
+		c.locker.Unlock()
+
+		return tlsConn, nil
+	})
+	if err != nil {
+		return err
+	}
+
+	c.isTLS = true
+	return nil
+}
+
+// SupportAuth checks if the server supports a given authentication mechanism.
+func (c *Client) SupportAuth(mech string) (bool, error) {
+	return c.Support("AUTH=" + mech)
+}
+
+// Authenticate indicates a SASL authentication mechanism to the server. If the
+// server supports the requested authentication mechanism, it performs an
+// authentication protocol exchange to authenticate and identify the client.
+func (c *Client) Authenticate(auth sasl.Client) error {
+	if c.State() != imap.NotAuthenticatedState {
+		return ErrAlreadyLoggedIn
+	}
+
+	mech, ir, err := auth.Start()
+	if err != nil {
+		return err
+	}
+
+	cmd := &commands.Authenticate{
+		Mechanism: mech,
+	}
+
+	irOk, err := c.Support("SASL-IR")
+	if err != nil {
+		return err
+	}
+	if irOk {
+		cmd.InitialResponse = ir
+	}
+
+	res := &responses.Authenticate{
+		Mechanism:       auth,
+		InitialResponse: ir,
+		RepliesCh:       make(chan []byte, 10),
+	}
+	if irOk {
+		res.InitialResponse = nil
+	}
+
+	status, err := c.execute(cmd, res)
+	if err != nil {
+		return err
+	}
+	if err = status.Err(); err != nil {
+		return err
+	}
+
+	c.locker.Lock()
+	c.state = imap.AuthenticatedState
+	c.caps = nil // Capabilities change when user is logged in
+	c.locker.Unlock()
+
+	if status.Code == "CAPABILITY" {
+		c.gotStatusCaps(status.Arguments)
+	}
+
+	return nil
+}
+
+// Login identifies the client to the server and carries the plaintext password
+// authenticating this user.
+func (c *Client) Login(username, password string) error {
+	if state := c.State(); state == imap.AuthenticatedState || state == imap.SelectedState {
+		return ErrAlreadyLoggedIn
+	}
+
+	c.locker.Lock()
+	loginDisabled := c.caps != nil && c.caps["LOGINDISABLED"]
+	c.locker.Unlock()
+	if loginDisabled {
+		return ErrLoginDisabled
+	}
+
+	cmd := &commands.Login{
+		Username: username,
+		Password: password,
+	}
+
+	status, err := c.execute(cmd, nil)
+	if err != nil {
+		return err
+	}
+	if err = status.Err(); err != nil {
+		return err
+	}
+
+	c.locker.Lock()
+	c.state = imap.AuthenticatedState
+	c.caps = nil // Capabilities change when user is logged in
+	c.locker.Unlock()
+
+	if status.Code == "CAPABILITY" {
+		c.gotStatusCaps(status.Arguments)
+	}
+	return nil
+}

client/cmd_noauth_test.go

@@ -0,0 +1,299 @@
+package client
+
+import (
+	"crypto/tls"
+	"io"
+	"testing"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/internal"
+	"github.com/emersion/go-sasl"
+)
+
+func TestClient_StartTLS(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	cert, err := tls.X509KeyPair(internal.LocalhostCert, internal.LocalhostKey)
+	if err != nil {
+		t.Fatal("cannot load test certificate:", err)
+	}
+
+	tlsConfig := &tls.Config{
+		InsecureSkipVerify: true,
+		Certificates:       []tls.Certificate{cert},
+	}
+
+	if c.IsTLS() {
+		t.Fatal("Client has TLS enabled before STARTTLS")
+	}
+
+	if ok, err := c.SupportStartTLS(); err != nil {
+		t.Fatalf("c.SupportStartTLS() = %v", err)
+	} else if !ok {
+		t.Fatalf("c.SupportStartTLS() = %v, want true", ok)
+	}
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.StartTLS(tlsConfig)
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "STARTTLS" {
+		t.Fatalf("client sent command %v, want STARTTLS", cmd)
+	}
+	s.WriteString(tag + " OK Begin TLS negotiation now\r\n")
+
+	ss := tls.Server(s.Conn, tlsConfig)
+	if err := ss.Handshake(); err != nil {
+		t.Fatal("cannot perform TLS handshake:", err)
+	}
+
+	if err := <-done; err != nil {
+		t.Error("c.StartTLS() =", err)
+	}
+
+	if !c.IsTLS() {
+		t.Errorf("Client has not TLS enabled after STARTTLS")
+	}
+
+	go func() {
+		_, err := c.Capability()
+		done <- err
+	}()
+
+	tag, cmd = newCmdScanner(ss).ScanCmd()
+	if cmd != "CAPABILITY" {
+		t.Fatalf("client sent command %v, want CAPABILITY", cmd)
+	}
+	io.WriteString(ss, "* CAPABILITY IMAP4rev1 AUTH=PLAIN\r\n")
+	io.WriteString(ss, tag+" OK CAPABILITY completed.\r\n")
+}
+
+func TestClient_Authenticate(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	if ok, err := c.SupportAuth(sasl.Plain); err != nil {
+		t.Fatalf("c.SupportAuth(sasl.Plain) = %v", err)
+	} else if !ok {
+		t.Fatalf("c.SupportAuth(sasl.Plain) = %v, want true", ok)
+	}
+
+	sasl := sasl.NewPlainClient("", "username", "password")
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Authenticate(sasl)
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "AUTHENTICATE PLAIN" {
+		t.Fatalf("client sent command %v, want AUTHENTICATE PLAIN", cmd)
+	}
+
+	s.WriteString("+ \r\n")
+
+	wantLine := "AHVzZXJuYW1lAHBhc3N3b3Jk"
+	if line := s.ScanLine(); line != wantLine {
+		t.Fatalf("client sent auth %v, want %v", line, wantLine)
+	}
+
+	s.WriteString(tag + " OK AUTHENTICATE completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Authenticate() = %v", err)
+	}
+
+	if state := c.State(); state != imap.AuthenticatedState {
+		t.Errorf("c.State() = %v, want %v", state, imap.AuthenticatedState)
+	}
+}
+
+func TestClient_Authenticate_InitialResponse(t *testing.T) {
+	c, s := newTestClientWithGreeting(t, "* OK [CAPABILITY IMAP4rev1 SASL-IR STARTTLS AUTH=PLAIN] Server ready.\r\n")
+	defer s.Close()
+
+	if ok, err := c.SupportAuth(sasl.Plain); err != nil {
+		t.Fatalf("c.SupportAuth(sasl.Plain) = %v", err)
+	} else if !ok {
+		t.Fatalf("c.SupportAuth(sasl.Plain) = %v, want true", ok)
+	}
+
+	sasl := sasl.NewPlainClient("", "username", "password")
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Authenticate(sasl)
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "AUTHENTICATE PLAIN AHVzZXJuYW1lAHBhc3N3b3Jk" {
+		t.Fatalf("client sent command %v, want AUTHENTICATE PLAIN AHVzZXJuYW1lAHBhc3N3b3Jk", cmd)
+	}
+
+	s.WriteString(tag + " OK AUTHENTICATE completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Authenticate() = %v", err)
+	}
+
+	if state := c.State(); state != imap.AuthenticatedState {
+		t.Errorf("c.State() = %v, want %v", state, imap.AuthenticatedState)
+	}
+}
+
+func TestClient_Login_Success(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Login("username", "password")
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "LOGIN \"username\" \"password\"" {
+		t.Fatalf("client sent command %v, want LOGIN username password", cmd)
+	}
+	s.WriteString(tag + " OK LOGIN completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Login() = %v", err)
+	}
+
+	if state := c.State(); state != imap.AuthenticatedState {
+		t.Errorf("c.State() = %v, want %v", state, imap.AuthenticatedState)
+	}
+}
+
+func TestClient_Login_8bitSync(t *testing.T) {
+	c, s := newTestClientWithGreeting(t, "* OK [CAPABILITY IMAP4rev1 SASL-IR STARTTLS AUTH=PLAIN] Server ready.\r\n")
+	defer s.Close()
+
+	// Use of UTF-8 will force go-imap to send password in literal.
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Login("username", "пароль")
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "LOGIN \"username\" {12}" {
+		t.Fatalf("client sent command %v, want LOGIN \"username\" {12}", cmd)
+	}
+	s.WriteString("+ send literal\r\n")
+	pass := s.ScanLine()
+	if pass != "пароль" {
+		t.Fatalf("client sent %v, want {12}'пароль' literal", pass)
+	}
+	s.WriteString(tag + " OK LOGIN completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Login() = %v", err)
+	}
+
+	if state := c.State(); state != imap.AuthenticatedState {
+		t.Errorf("c.State() = %v, want %v", state, imap.AuthenticatedState)
+	}
+}
+
+func TestClient_Login_8bitNonSync(t *testing.T) {
+	c, s := newTestClientWithGreeting(t, "* OK [CAPABILITY IMAP4rev1 LITERAL- SASL-IR STARTTLS AUTH=PLAIN] Server ready.\r\n")
+	defer s.Close()
+
+	// Use of UTF-8 will force go-imap to send password in literal.
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Login("username", "пароль")
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "LOGIN \"username\" {12+}" {
+		t.Fatalf("client sent command %v, want LOGIN \"username\" {12+}", cmd)
+	}
+	pass := s.ScanLine()
+	if pass != "пароль" {
+		t.Fatalf("client sent %v, want {12+}'пароль' literal", pass)
+	}
+	s.WriteString(tag + " OK LOGIN completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Login() = %v", err)
+	}
+
+	if state := c.State(); state != imap.AuthenticatedState {
+		t.Errorf("c.State() = %v, want %v", state, imap.AuthenticatedState)
+	}
+}
+
+func TestClient_Login_Error(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Login("username", "password")
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "LOGIN \"username\" \"password\"" {
+		t.Fatalf("client sent command %v, want LOGIN username password", cmd)
+	}
+	s.WriteString(tag + " NO LOGIN incorrect\r\n")
+
+	if err := <-done; err == nil {
+		t.Fatal("c.Login() = nil, want LOGIN incorrect")
+	}
+
+	if state := c.State(); state != imap.NotAuthenticatedState {
+		t.Errorf("c.State() = %v, want %v", state, imap.NotAuthenticatedState)
+	}
+}
+
+func TestClient_Login_State_Allowed(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Login("username", "password")
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "LOGIN \"username\" \"password\"" {
+		t.Fatalf("client sent command %v, want LOGIN \"username\" \"password\"", cmd)
+	}
+	s.WriteString(tag + " OK LOGIN completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Login() = %v", err)
+	}
+
+	if state := c.State(); state != imap.AuthenticatedState {
+		t.Errorf("c.State() = %v, want %v", state, imap.AuthenticatedState)
+	}
+
+	go func() {
+		done <- c.Login("username", "password")
+	}()
+	if err := <-done; err != ErrAlreadyLoggedIn {
+		t.Fatalf("c.Login() = %v, want %v", err, ErrAlreadyLoggedIn)
+	}
+
+	go func() {
+		done <- c.Logout()
+	}()
+
+	s.ScanCmd()
+	s.WriteString("* BYE Client asked to close the connection.\r\n")
+	s.WriteString(tag + " OK LOGOUT completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Logout() = %v", err)
+	}
+
+	if err := c.Login("username", "password"); err == ErrAlreadyLoggedIn {
+		t.Errorf("Client is logout, login must not give %v", ErrAlreadyLoggedIn)
+	}
+}

client/cmd_selected.go

@@ -0,0 +1,372 @@
+package client
+
+import (
+	"errors"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/commands"
+	"github.com/emersion/go-imap/responses"
+)
+
+var (
+	// ErrNoMailboxSelected is returned if a command that requires a mailbox to be
+	// selected is called when there isn't.
+	ErrNoMailboxSelected = errors.New("No mailbox selected")
+
+	// ErrExtensionUnsupported is returned if a command uses a extension that
+	// is not supported by the server.
+	ErrExtensionUnsupported = errors.New("The required extension is not supported by the server")
+)
+
+// Check requests a checkpoint of the currently selected mailbox. A checkpoint
+// refers to any implementation-dependent housekeeping associated with the
+// mailbox that is not normally executed as part of each command.
+func (c *Client) Check() error {
+	if c.State() != imap.SelectedState {
+		return ErrNoMailboxSelected
+	}
+
+	cmd := new(commands.Check)
+
+	status, err := c.execute(cmd, nil)
+	if err != nil {
+		return err
+	}
+
+	return status.Err()
+}
+
+// Close permanently removes all messages that have the \Deleted flag set from
+// the currently selected mailbox, and returns to the authenticated state from
+// the selected state.
+func (c *Client) Close() error {
+	if c.State() != imap.SelectedState {
+		return ErrNoMailboxSelected
+	}
+
+	cmd := new(commands.Close)
+
+	status, err := c.execute(cmd, nil)
+	if err != nil {
+		return err
+	} else if err := status.Err(); err != nil {
+		return err
+	}
+
+	c.locker.Lock()
+	c.state = imap.AuthenticatedState
+	c.mailbox = nil
+	c.locker.Unlock()
+	return nil
+}
+
+// Terminate closes the tcp connection
+func (c *Client) Terminate() error {
+	return c.conn.Close()
+}
+
+// Expunge permanently removes all messages that have the \Deleted flag set from
+// the currently selected mailbox. If ch is not nil, sends sequence IDs of each
+// deleted message to this channel.
+func (c *Client) Expunge(ch chan uint32) error {
+	if ch != nil {
+		defer close(ch)
+	}
+
+	if c.State() != imap.SelectedState {
+		return ErrNoMailboxSelected
+	}
+
+	cmd := new(commands.Expunge)
+
+	var h responses.Handler
+	if ch != nil {
+		h = &responses.Expunge{SeqNums: ch}
+	}
+
+	status, err := c.execute(cmd, h)
+	if err != nil {
+		return err
+	}
+	return status.Err()
+}
+
+func (c *Client) executeSearch(uid bool, criteria *imap.SearchCriteria, charset string) (ids []uint32, status *imap.StatusResp, err error) {
+	if c.State() != imap.SelectedState {
+		err = ErrNoMailboxSelected
+		return
+	}
+
+	var cmd imap.Commander = &commands.Search{
+		Charset:  charset,
+		Criteria: criteria,
+	}
+	if uid {
+		cmd = &commands.Uid{Cmd: cmd}
+	}
+
+	res := new(responses.Search)
+
+	status, err = c.execute(cmd, res)
+	if err != nil {
+		return
+	}
+
+	err, ids = status.Err(), res.Ids
+	return
+}
+
+func (c *Client) search(uid bool, criteria *imap.SearchCriteria) (ids []uint32, err error) {
+	charset := "UTF-8"
+	if c.utf8SearchUnsupported {
+		charset = "US-ASCII"
+	}
+	ids, status, err := c.executeSearch(uid, criteria, charset)
+	if status != nil && status.Code == imap.CodeBadCharset {
+		// Some servers don't support UTF-8
+		ids, _, err = c.executeSearch(uid, criteria, "US-ASCII")
+		c.utf8SearchUnsupported = true
+	}
+	return
+}
+
+// Search searches the mailbox for messages that match the given searching
+// criteria. Searching criteria consist of one or more search keys. The response
+// contains a list of message sequence IDs corresponding to those messages that
+// match the searching criteria. When multiple keys are specified, the result is
+// the intersection (AND function) of all the messages that match those keys.
+// Criteria must be UTF-8 encoded. See RFC 3501 section 6.4.4 for a list of
+// searching criteria. When no criteria has been set, all messages in the mailbox
+// will be searched using ALL criteria.
+func (c *Client) Search(criteria *imap.SearchCriteria) (seqNums []uint32, err error) {
+	return c.search(false, criteria)
+}
+
+// UidSearch is identical to Search, but UIDs are returned instead of message
+// sequence numbers.
+func (c *Client) UidSearch(criteria *imap.SearchCriteria) (uids []uint32, err error) {
+	return c.search(true, criteria)
+}
+
+func (c *Client) fetch(uid bool, seqset *imap.SeqSet, items []imap.FetchItem, ch chan *imap.Message) error {
+	defer close(ch)
+
+	if c.State() != imap.SelectedState {
+		return ErrNoMailboxSelected
+	}
+
+	var cmd imap.Commander = &commands.Fetch{
+		SeqSet: seqset,
+		Items:  items,
+	}
+	if uid {
+		cmd = &commands.Uid{Cmd: cmd}
+	}
+
+	res := &responses.Fetch{Messages: ch, SeqSet: seqset, Uid: uid}
+
+	status, err := c.execute(cmd, res)
+	if err != nil {
+		return err
+	}
+	return status.Err()
+}
+
+// Fetch retrieves data associated with a message in the mailbox. See RFC 3501
+// section 6.4.5 for a list of items that can be requested.
+func (c *Client) Fetch(seqset *imap.SeqSet, items []imap.FetchItem, ch chan *imap.Message) error {
+	return c.fetch(false, seqset, items, ch)
+}
+
+// UidFetch is identical to Fetch, but seqset is interpreted as containing
+// unique identifiers instead of message sequence numbers.
+func (c *Client) UidFetch(seqset *imap.SeqSet, items []imap.FetchItem, ch chan *imap.Message) error {
+	return c.fetch(true, seqset, items, ch)
+}
+
+func (c *Client) store(uid bool, seqset *imap.SeqSet, item imap.StoreItem, value interface{}, ch chan *imap.Message) error {
+	if ch != nil {
+		defer close(ch)
+	}
+
+	if c.State() != imap.SelectedState {
+		return ErrNoMailboxSelected
+	}
+
+	// TODO: this could break extensions (this only works when item is FLAGS)
+	if fields, ok := value.([]interface{}); ok {
+		for i, field := range fields {
+			if s, ok := field.(string); ok {
+				fields[i] = imap.RawString(s)
+			}
+		}
+	}
+
+	// If ch is nil, the updated values are data which will be lost, so don't
+	// retrieve it.
+	if ch == nil {
+		op, _, err := imap.ParseFlagsOp(item)
+		if err == nil {
+			item = imap.FormatFlagsOp(op, true)
+		}
+	}
+
+	var cmd imap.Commander = &commands.Store{
+		SeqSet: seqset,
+		Item:   item,
+		Value:  value,
+	}
+	if uid {
+		cmd = &commands.Uid{Cmd: cmd}
+	}
+
+	var h responses.Handler
+	if ch != nil {
+		h = &responses.Fetch{Messages: ch, SeqSet: seqset, Uid: uid}
+	}
+
+	status, err := c.execute(cmd, h)
+	if err != nil {
+		return err
+	}
+	return status.Err()
+}
+
+// Store alters data associated with a message in the mailbox. If ch is not nil,
+// the updated value of the data will be sent to this channel. See RFC 3501
+// section 6.4.6 for a list of items that can be updated.
+func (c *Client) Store(seqset *imap.SeqSet, item imap.StoreItem, value interface{}, ch chan *imap.Message) error {
+	return c.store(false, seqset, item, value, ch)
+}
+
+// UidStore is identical to Store, but seqset is interpreted as containing
+// unique identifiers instead of message sequence numbers.
+func (c *Client) UidStore(seqset *imap.SeqSet, item imap.StoreItem, value interface{}, ch chan *imap.Message) error {
+	return c.store(true, seqset, item, value, ch)
+}
+
+func (c *Client) copy(uid bool, seqset *imap.SeqSet, dest string) error {
+	if c.State() != imap.SelectedState {
+		return ErrNoMailboxSelected
+	}
+
+	var cmd imap.Commander = &commands.Copy{
+		SeqSet:  seqset,
+		Mailbox: dest,
+	}
+	if uid {
+		cmd = &commands.Uid{Cmd: cmd}
+	}
+
+	status, err := c.execute(cmd, nil)
+	if err != nil {
+		return err
+	}
+	return status.Err()
+}
+
+// Copy copies the specified message(s) to the end of the specified destination
+// mailbox.
+func (c *Client) Copy(seqset *imap.SeqSet, dest string) error {
+	return c.copy(false, seqset, dest)
+}
+
+// UidCopy is identical to Copy, but seqset is interpreted as containing unique
+// identifiers instead of message sequence numbers.
+func (c *Client) UidCopy(seqset *imap.SeqSet, dest string) error {
+	return c.copy(true, seqset, dest)
+}
+
+func (c *Client) move(uid bool, seqset *imap.SeqSet, dest string) error {
+	if c.State() != imap.SelectedState {
+		return ErrNoMailboxSelected
+	}
+
+	if ok, err := c.Support("MOVE"); err != nil {
+		return err
+	} else if !ok {
+		return c.moveFallback(uid, seqset, dest)
+	}
+
+	var cmd imap.Commander = &commands.Move{
+		SeqSet:  seqset,
+		Mailbox: dest,
+	}
+	if uid {
+		cmd = &commands.Uid{Cmd: cmd}
+	}
+
+	if status, err := c.Execute(cmd, nil); err != nil {
+		return err
+	} else {
+		return status.Err()
+	}
+}
+
+// moveFallback uses COPY, STORE and EXPUNGE for servers which don't support
+// MOVE.
+func (c *Client) moveFallback(uid bool, seqset *imap.SeqSet, dest string) error {
+	item := imap.FormatFlagsOp(imap.AddFlags, true)
+	flags := []interface{}{imap.DeletedFlag}
+	if uid {
+		if err := c.UidCopy(seqset, dest); err != nil {
+			return err
+		}
+
+		if err := c.UidStore(seqset, item, flags, nil); err != nil {
+			return err
+		}
+	} else {
+		if err := c.Copy(seqset, dest); err != nil {
+			return err
+		}
+
+		if err := c.Store(seqset, item, flags, nil); err != nil {
+			return err
+		}
+	}
+
+	return c.Expunge(nil)
+}
+
+// Move moves the specified message(s) to the end of the specified destination
+// mailbox.
+//
+// If the server doesn't support the MOVE extension defined in RFC 6851,
+// go-imap will fallback to copy, store and expunge.
+func (c *Client) Move(seqset *imap.SeqSet, dest string) error {
+	return c.move(false, seqset, dest)
+}
+
+// UidMove is identical to Move, but seqset is interpreted as containing unique
+// identifiers instead of message sequence numbers.
+func (c *Client) UidMove(seqset *imap.SeqSet, dest string) error {
+	return c.move(true, seqset, dest)
+}
+
+// Unselect frees server's resources associated with the selected mailbox and
+// returns the server to the authenticated state. This command performs the same
+// actions as Close, except that no messages are permanently removed from the
+// currently selected mailbox.
+//
+// If client does not support the UNSELECT extension, ErrExtensionUnsupported
+// is returned.
+func (c *Client) Unselect() error {
+	if ok, err := c.Support("UNSELECT"); !ok || err != nil {
+		return ErrExtensionUnsupported
+	}
+
+	if c.State() != imap.SelectedState {
+		return ErrNoMailboxSelected
+	}
+
+	cmd := &commands.Unselect{}
+	if status, err := c.Execute(cmd, nil); err != nil {
+		return err
+	} else if err := status.Err(); err != nil {
+		return err
+	}
+
+	c.SetState(imap.AuthenticatedState, nil)
+	return nil
+}

client/cmd_selected_test.go

@@ -0,0 +1,816 @@
+package client
+
+import (
+	"io/ioutil"
+	"net/textproto"
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/emersion/go-imap"
+)
+
+func TestClient_Check(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Check()
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "CHECK" {
+		t.Fatalf("client sent command %v, want %v", cmd, "CHECK")
+	}
+
+	s.WriteString(tag + " OK CHECK completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Check() = %v", err)
+	}
+}
+
+func TestClient_Close(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, &imap.MailboxStatus{Name: "INBOX"})
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Close()
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "CLOSE" {
+		t.Fatalf("client sent command %v, want %v", cmd, "CLOSE")
+	}
+
+	s.WriteString(tag + " OK CLOSE completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Check() = %v", err)
+	}
+
+	if state := c.State(); state != imap.AuthenticatedState {
+		t.Errorf("Bad state: %v", state)
+	}
+	if mailbox := c.Mailbox(); mailbox != nil {
+		t.Errorf("Client selected mailbox is not nil: %v", mailbox)
+	}
+}
+
+func TestClient_Expunge(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	done := make(chan error, 1)
+	expunged := make(chan uint32, 4)
+	go func() {
+		done <- c.Expunge(expunged)
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "EXPUNGE" {
+		t.Fatalf("client sent command %v, want %v", cmd, "EXPUNGE")
+	}
+
+	s.WriteString("* 3 EXPUNGE\r\n")
+	s.WriteString("* 3 EXPUNGE\r\n")
+	s.WriteString("* 5 EXPUNGE\r\n")
+	s.WriteString("* 8 EXPUNGE\r\n")
+	s.WriteString(tag + " OK EXPUNGE completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Expunge() = %v", err)
+	}
+
+	expected := []uint32{3, 3, 5, 8}
+
+	i := 0
+	for id := range expunged {
+		if id != expected[i] {
+			t.Errorf("Bad expunged sequence number: got %v instead of %v", id, expected[i])
+		}
+		i++
+	}
+}
+
+func TestClient_Search(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	date, _ := time.Parse(imap.DateLayout, "1-Feb-1994")
+	criteria := &imap.SearchCriteria{
+		WithFlags: []string{imap.DeletedFlag},
+		Header:    textproto.MIMEHeader{"From": {"Smith"}},
+		Since:     date,
+		Not: []*imap.SearchCriteria{{
+			Header: textproto.MIMEHeader{"To": {"Pauline"}},
+		}},
+	}
+
+	done := make(chan error, 1)
+	var results []uint32
+	go func() {
+		var err error
+		results, err = c.Search(criteria)
+		done <- err
+	}()
+
+	wantCmd := `SEARCH CHARSET UTF-8 SINCE "1-Feb-1994" FROM "Smith" DELETED NOT (TO "Pauline")`
+	tag, cmd := s.ScanCmd()
+	if cmd != wantCmd {
+		t.Fatalf("client sent command %v, want %v", cmd, wantCmd)
+	}
+
+	s.WriteString("* SEARCH 2 84 882\r\n")
+	s.WriteString(tag + " OK SEARCH completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Search() = %v", err)
+	}
+
+	want := []uint32{2, 84, 882}
+	if !reflect.DeepEqual(results, want) {
+		t.Errorf("c.Search() = %v, want %v", results, want)
+	}
+}
+
+func TestClient_Search_Badcharset(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	date, _ := time.Parse(imap.DateLayout, "1-Feb-1994")
+	criteria := &imap.SearchCriteria{
+		WithFlags: []string{imap.DeletedFlag},
+		Header:    textproto.MIMEHeader{"From": {"Smith"}},
+		Since:     date,
+		Not: []*imap.SearchCriteria{{
+			Header: textproto.MIMEHeader{"To": {"Pauline"}},
+		}},
+	}
+
+	done := make(chan error, 1)
+	var results []uint32
+	go func() {
+		var err error
+		results, err = c.Search(criteria)
+		done <- err
+	}()
+
+	// first search call with default UTF-8 charset (assume server does not support UTF-8)
+	wantCmd := `SEARCH CHARSET UTF-8 SINCE "1-Feb-1994" FROM "Smith" DELETED NOT (TO "Pauline")`
+	tag, cmd := s.ScanCmd()
+	if cmd != wantCmd {
+		t.Fatalf("client sent command %v, want %v", cmd, wantCmd)
+	}
+
+	s.WriteString(tag + " NO [BADCHARSET (US-ASCII)]\r\n")
+
+	// internal fall-back to US-ASCII which sets utf8SearchUnsupported = true
+	wantCmd = `SEARCH CHARSET US-ASCII SINCE "1-Feb-1994" FROM "Smith" DELETED NOT (TO "Pauline")`
+	tag, cmd = s.ScanCmd()
+	if cmd != wantCmd {
+		t.Fatalf("client sent command %v, want %v", cmd, wantCmd)
+	}
+
+	s.WriteString("* SEARCH 2 84 882\r\n")
+	s.WriteString(tag + " OK SEARCH completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	want := []uint32{2, 84, 882}
+	if !reflect.DeepEqual(results, want) {
+		t.Errorf("c.Search() = %v, want %v", results, want)
+	}
+
+	if !c.utf8SearchUnsupported {
+		t.Fatal("client should have utf8SearchUnsupported set to true")
+	}
+
+	// second call to search (with utf8SearchUnsupported=true)
+	go func() {
+		var err error
+		results, err = c.Search(criteria)
+		done <- err
+	}()
+
+	tag, cmd = s.ScanCmd()
+	if cmd != wantCmd {
+		t.Fatalf("client sent command %v, want %v", cmd, wantCmd)
+	}
+
+	s.WriteString("* SEARCH 2 84 882\r\n")
+	s.WriteString(tag + " OK SEARCH completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Search() = %v", err)
+	}
+
+	if !reflect.DeepEqual(results, want) {
+		t.Errorf("c.Search() = %v, want %v", results, want)
+	}
+}
+
+func TestClient_Search_Uid(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	criteria := &imap.SearchCriteria{
+		WithoutFlags: []string{imap.DeletedFlag},
+	}
+
+	done := make(chan error, 1)
+	var results []uint32
+	go func() {
+		var err error
+		results, err = c.UidSearch(criteria)
+		done <- err
+	}()
+
+	wantCmd := "UID SEARCH CHARSET UTF-8 UNDELETED"
+	tag, cmd := s.ScanCmd()
+	if cmd != wantCmd {
+		t.Fatalf("client sent command %v, want %v", cmd, wantCmd)
+	}
+
+	s.WriteString("* SEARCH 1 78 2010\r\n")
+	s.WriteString(tag + " OK UID SEARCH completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Search() = %v", err)
+	}
+
+	want := []uint32{1, 78, 2010}
+	if !reflect.DeepEqual(results, want) {
+		t.Errorf("c.Search() = %v, want %v", results, want)
+	}
+}
+
+func TestClient_Search_Uid_Badcharset(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	criteria := &imap.SearchCriteria{
+		WithoutFlags: []string{imap.DeletedFlag},
+	}
+
+	done := make(chan error, 1)
+	var results []uint32
+	go func() {
+		var err error
+		results, err = c.UidSearch(criteria)
+		done <- err
+	}()
+
+	// first search call with default UTF-8 charset (assume server does not support UTF-8)
+	wantCmd := "UID SEARCH CHARSET UTF-8 UNDELETED"
+	tag, cmd := s.ScanCmd()
+	if cmd != wantCmd {
+		t.Fatalf("client sent command %v, want %v", cmd, wantCmd)
+	}
+
+	s.WriteString(tag + " NO [BADCHARSET (US-ASCII)]\r\n")
+
+	// internal fall-back to US-ASCII which sets utf8SearchUnsupported = true
+	wantCmd = "UID SEARCH CHARSET US-ASCII UNDELETED"
+	tag, cmd = s.ScanCmd()
+	if cmd != wantCmd {
+		t.Fatalf("client sent command %v, want %v", cmd, wantCmd)
+	}
+
+	s.WriteString("* SEARCH 1 78 2010\r\n")
+	s.WriteString(tag + " OK UID SEARCH completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.UidSearch() = %v", err)
+	}
+
+	want := []uint32{1, 78, 2010}
+	if !reflect.DeepEqual(results, want) {
+		t.Errorf("c.UidSearch() = %v, want %v", results, want)
+	}
+
+	if !c.utf8SearchUnsupported {
+		t.Fatal("client should have utf8SearchUnsupported set to true")
+	}
+
+	// second call to search (with utf8SearchUnsupported=true)
+	go func() {
+		var err error
+		results, err = c.UidSearch(criteria)
+		done <- err
+	}()
+
+	tag, cmd = s.ScanCmd()
+	if cmd != wantCmd {
+		t.Fatalf("client sent command %v, want %v", cmd, wantCmd)
+	}
+
+	s.WriteString("* SEARCH 1 78 2010\r\n")
+	s.WriteString(tag + " OK UID SEARCH completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.UidSearch() = %v", err)
+	}
+
+	if !reflect.DeepEqual(results, want) {
+		t.Errorf("c.UidSearch() = %v, want %v", results, want)
+	}
+
+}
+
+func TestClient_Fetch(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	seqset, _ := imap.ParseSeqSet("2:3")
+	fields := []imap.FetchItem{imap.FetchUid, imap.FetchItem("BODY[]")}
+
+	done := make(chan error, 1)
+	messages := make(chan *imap.Message, 2)
+	go func() {
+		done <- c.Fetch(seqset, fields, messages)
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "FETCH 2:3 (UID BODY[])" {
+		t.Fatalf("client sent command %v, want %v", cmd, "FETCH 2:3 (UID BODY[])")
+	}
+
+	s.WriteString("* 2 FETCH (UID 42 BODY[] {16}\r\n")
+	s.WriteString("I love potatoes.")
+	s.WriteString(")\r\n")
+
+	s.WriteString("* 3 FETCH (UID 28 BODY[] {12}\r\n")
+	s.WriteString("Hello World!")
+	s.WriteString(")\r\n")
+
+	s.WriteString(tag + " OK FETCH completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Fetch() = %v", err)
+	}
+
+	section, _ := imap.ParseBodySectionName("BODY[]")
+
+	msg := <-messages
+	if msg.SeqNum != 2 {
+		t.Errorf("First message has bad sequence number: %v", msg.SeqNum)
+	}
+	if msg.Uid != 42 {
+		t.Errorf("First message has bad UID: %v", msg.Uid)
+	}
+	if body, _ := ioutil.ReadAll(msg.GetBody(section)); string(body) != "I love potatoes." {
+		t.Errorf("First message has bad body: %q", body)
+	}
+
+	msg = <-messages
+	if msg.SeqNum != 3 {
+		t.Errorf("First message has bad sequence number: %v", msg.SeqNum)
+	}
+	if msg.Uid != 28 {
+		t.Errorf("Second message has bad UID: %v", msg.Uid)
+	}
+	if body, _ := ioutil.ReadAll(msg.GetBody(section)); string(body) != "Hello World!" {
+		t.Errorf("Second message has bad body: %q", body)
+	}
+}
+
+func TestClient_Fetch_ClosedState(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.AuthenticatedState, nil)
+
+	seqset, _ := imap.ParseSeqSet("2:3")
+	fields := []imap.FetchItem{imap.FetchUid, imap.FetchItem("BODY[]")}
+
+	done := make(chan error, 1)
+	messages := make(chan *imap.Message, 2)
+	go func() {
+		done <- c.Fetch(seqset, fields, messages)
+	}()
+
+	_, more := <-messages
+
+	if more {
+		t.Fatalf("Messages channel has more messages, but it must be closed with no messages sent")
+	}
+
+	err := <-done
+
+	if err != ErrNoMailboxSelected {
+		t.Fatalf("Expected error to be IMAP Client ErrNoMailboxSelected")
+	}
+}
+
+func TestClient_Fetch_Partial(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	seqset, _ := imap.ParseSeqSet("1")
+	fields := []imap.FetchItem{imap.FetchItem("BODY.PEEK[]<0.10>")}
+
+	done := make(chan error, 1)
+	messages := make(chan *imap.Message, 1)
+	go func() {
+		done <- c.Fetch(seqset, fields, messages)
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "FETCH 1 (BODY.PEEK[]<0.10>)" {
+		t.Fatalf("client sent command %v, want %v", cmd, "FETCH 1 (BODY.PEEK[]<0.10>)")
+	}
+
+	s.WriteString("* 1 FETCH (BODY[]<0> {10}\r\n")
+	s.WriteString("I love pot")
+	s.WriteString(")\r\n")
+
+	s.WriteString(tag + " OK FETCH completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Fetch() = %v", err)
+	}
+
+	section, _ := imap.ParseBodySectionName("BODY.PEEK[]<0.10>")
+
+	msg := <-messages
+	if body, _ := ioutil.ReadAll(msg.GetBody(section)); string(body) != "I love pot" {
+		t.Errorf("Message has bad body: %q", body)
+	}
+}
+
+func TestClient_Fetch_part(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	seqset, _ := imap.ParseSeqSet("1")
+	fields := []imap.FetchItem{imap.FetchItem("BODY.PEEK[1]")}
+
+	done := make(chan error, 1)
+	messages := make(chan *imap.Message, 1)
+	go func() {
+		done <- c.Fetch(seqset, fields, messages)
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "FETCH 1 (BODY.PEEK[1])" {
+		t.Fatalf("client sent command %v, want %v", cmd, "FETCH 1 (BODY.PEEK[1])")
+	}
+
+	s.WriteString("* 1 FETCH (BODY[1] {3}\r\n")
+	s.WriteString("Hey")
+	s.WriteString(")\r\n")
+
+	s.WriteString(tag + " OK FETCH completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Fetch() = %v", err)
+	}
+
+	<-messages
+}
+
+func TestClient_Fetch_Uid(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	seqset, _ := imap.ParseSeqSet("1:867")
+	fields := []imap.FetchItem{imap.FetchFlags}
+
+	done := make(chan error, 1)
+	messages := make(chan *imap.Message, 1)
+	go func() {
+		done <- c.UidFetch(seqset, fields, messages)
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "UID FETCH 1:867 (FLAGS)" {
+		t.Fatalf("client sent command %v, want %v", cmd, "UID FETCH 1:867 (FLAGS)")
+	}
+
+	s.WriteString("* 23 FETCH (UID 42 FLAGS (\\Seen))\r\n")
+	s.WriteString(tag + " OK UID FETCH completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.UidFetch() = %v", err)
+	}
+
+	msg := <-messages
+	if msg.SeqNum != 23 {
+		t.Errorf("First message has bad sequence number: %v", msg.SeqNum)
+	}
+	if msg.Uid != 42 {
+		t.Errorf("Message has bad UID: %v", msg.Uid)
+	}
+	if len(msg.Flags) != 1 || msg.Flags[0] != "\\Seen" {
+		t.Errorf("Message has bad flags: %v", msg.Flags)
+	}
+}
+
+func TestClient_Fetch_Unilateral(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	seqset, _ := imap.ParseSeqSet("1:4")
+	fields := []imap.FetchItem{imap.FetchFlags}
+
+	done := make(chan error, 1)
+	messages := make(chan *imap.Message, 3)
+	go func() {
+		done <- c.Fetch(seqset, fields, messages)
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "FETCH 1:4 (FLAGS)" {
+		t.Fatalf("client sent command %v, want %v", cmd, "FETCH 1:4 (FLAGS)")
+	}
+
+	s.WriteString("* 2 FETCH (FLAGS (\\Seen))\r\n")
+	s.WriteString("* 123 FETCH (FLAGS (\\Deleted))\r\n")
+	s.WriteString("* 4 FETCH (FLAGS (\\Seen))\r\n")
+	s.WriteString(tag + " OK FETCH completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Fetch() = %v", err)
+	}
+
+	msg := <-messages
+	if msg.SeqNum != 2 {
+		t.Errorf("First message has bad sequence number: %v", msg.SeqNum)
+	}
+	msg = <-messages
+	if msg.SeqNum != 4 {
+		t.Errorf("Second message has bad sequence number: %v", msg.SeqNum)
+	}
+
+	_, ok := <-messages
+	if ok {
+		t.Errorf("More than two messages")
+	}
+}
+
+func TestClient_Fetch_Unilateral_Uid(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	seqset, _ := imap.ParseSeqSet("1:4")
+	fields := []imap.FetchItem{imap.FetchFlags}
+
+	done := make(chan error, 1)
+	messages := make(chan *imap.Message, 3)
+	go func() {
+		done <- c.UidFetch(seqset, fields, messages)
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "UID FETCH 1:4 (FLAGS)" {
+		t.Fatalf("client sent command %v, want %v", cmd, "UID FETCH 1:4 (FLAGS)")
+	}
+
+	s.WriteString("* 23 FETCH (UID 2 FLAGS (\\Seen))\r\n")
+	s.WriteString("* 123 FETCH (FLAGS (\\Deleted))\r\n")
+	s.WriteString("* 49 FETCH (UID 4 FLAGS (\\Seen))\r\n")
+	s.WriteString(tag + " OK FETCH completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Fetch() = %v", err)
+	}
+
+	msg := <-messages
+	if msg.Uid != 2 {
+		t.Errorf("First message has bad UID: %v", msg.Uid)
+	}
+	msg = <-messages
+	if msg.Uid != 4 {
+		t.Errorf("Second message has bad UID: %v", msg.Uid)
+	}
+
+	_, ok := <-messages
+	if ok {
+		t.Errorf("More than two messages")
+	}
+}
+
+func TestClient_Fetch_Uid_Dynamic(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	seqset, _ := imap.ParseSeqSet("4:*")
+	fields := []imap.FetchItem{imap.FetchFlags}
+
+	done := make(chan error, 1)
+	messages := make(chan *imap.Message, 1)
+	go func() {
+		done <- c.UidFetch(seqset, fields, messages)
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "UID FETCH 4:* (FLAGS)" {
+		t.Fatalf("client sent command %v, want %v", cmd, "UID FETCH 4:* (FLAGS)")
+	}
+
+	s.WriteString("* 23 FETCH (UID 2 FLAGS (\\Seen))\r\n")
+	s.WriteString(tag + " OK FETCH completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Fetch() = %v", err)
+	}
+
+	msg, ok := <-messages
+	if !ok {
+		t.Errorf("No message supplied")
+	} else if msg.Uid != 2 {
+		t.Errorf("First message has bad UID: %v", msg.Uid)
+	}
+}
+
+func TestClient_Store(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	seqset, _ := imap.ParseSeqSet("2")
+
+	done := make(chan error, 1)
+	updates := make(chan *imap.Message, 1)
+	go func() {
+		done <- c.Store(seqset, imap.AddFlags, []interface{}{imap.SeenFlag, "foobar"}, updates)
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "STORE 2 +FLAGS (\\Seen foobar)" {
+		t.Fatalf("client sent command %v, want %v", cmd, "STORE 2 +FLAGS (\\Seen foobar)")
+	}
+
+	s.WriteString("* 2 FETCH (FLAGS (\\Seen foobar))\r\n")
+	s.WriteString(tag + " OK STORE completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Store() = %v", err)
+	}
+
+	msg := <-updates
+	if len(msg.Flags) != 2 || msg.Flags[0] != "\\Seen" || msg.Flags[1] != "foobar" {
+		t.Errorf("Bad message flags: %v", msg.Flags)
+	}
+}
+
+func TestClient_Store_Silent(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	seqset, _ := imap.ParseSeqSet("2:3")
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Store(seqset, imap.AddFlags, []interface{}{imap.SeenFlag, "foobar"}, nil)
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "STORE 2:3 +FLAGS.SILENT (\\Seen foobar)" {
+		t.Fatalf("client sent command %v, want %v", cmd, "STORE 2:3 +FLAGS.SILENT (\\Seen foobar)")
+	}
+
+	s.WriteString(tag + " OK STORE completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Store() = %v", err)
+	}
+}
+
+func TestClient_Store_Uid(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	seqset, _ := imap.ParseSeqSet("27:901")
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.UidStore(seqset, imap.AddFlags, []interface{}{imap.DeletedFlag, "foobar"}, nil)
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "UID STORE 27:901 +FLAGS.SILENT (\\Deleted foobar)" {
+		t.Fatalf("client sent command %v, want %v", cmd, "UID STORE 27:901 +FLAGS.SILENT (\\Deleted foobar)")
+	}
+
+	s.WriteString(tag + " OK STORE completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.UidStore() = %v", err)
+	}
+}
+
+func TestClient_Copy(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	seqset, _ := imap.ParseSeqSet("2:4")
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Copy(seqset, "Sent")
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "COPY 2:4 \"Sent\"" {
+		t.Fatalf("client sent command %v, want %v", cmd, "COPY 2:4 \"Sent\"")
+	}
+
+	s.WriteString(tag + " OK COPY completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Copy() = %v", err)
+	}
+}
+
+func TestClient_Copy_Uid(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	seqset, _ := imap.ParseSeqSet("78:102")
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.UidCopy(seqset, "Drafts")
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "UID COPY 78:102 \"Drafts\"" {
+		t.Fatalf("client sent command %v, want %v", cmd, "UID COPY 78:102 \"Drafts\"")
+	}
+
+	s.WriteString(tag + " OK UID COPY completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.UidCopy() = %v", err)
+	}
+}
+
+func TestClient_Unselect(t *testing.T) {
+	c, s := newTestClient(t)
+	defer s.Close()
+
+	setClientState(c, imap.SelectedState, nil)
+
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Unselect()
+	}()
+
+	tag, cmd := s.ScanCmd()
+	if cmd != "UNSELECT" {
+		t.Fatalf("client sent command %v, want %v", cmd, "UNSELECT")
+	}
+
+	s.WriteString(tag + " OK UNSELECT completed\r\n")
+
+	if err := <-done; err != nil {
+		t.Fatalf("c.Unselect() = %v", err)
+	}
+
+	if c.State() != imap.AuthenticatedState {
+		t.Fatal("Client is not Authenticated after UNSELECT")
+	}
+}

client/example_test.go

@@ -0,0 +1,323 @@
+package client_test
+
+import (
+	"bytes"
+	"crypto/tls"
+	"io/ioutil"
+	"log"
+	"net/mail"
+	"time"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/client"
+)
+
+func ExampleClient() {
+	log.Println("Connecting to server...")
+
+	// Connect to server
+	c, err := client.DialTLS("mail.example.org:993", nil)
+	if err != nil {
+		log.Fatal(err)
+	}
+	log.Println("Connected")
+
+	// Don't forget to logout
+	defer c.Logout()
+
+	// Login
+	if err := c.Login("username", "password"); err != nil {
+		log.Fatal(err)
+	}
+	log.Println("Logged in")
+
+	// List mailboxes
+	mailboxes := make(chan *imap.MailboxInfo, 10)
+	done := make(chan error, 1)
+	go func() {
+		done <- c.List("", "*", mailboxes)
+	}()
+
+	log.Println("Mailboxes:")
+	for m := range mailboxes {
+		log.Println("* " + m.Name)
+	}
+
+	if err := <-done; err != nil {
+		log.Fatal(err)
+	}
+
+	// Select INBOX
+	mbox, err := c.Select("INBOX", false)
+	if err != nil {
+		log.Fatal(err)
+	}
+	log.Println("Flags for INBOX:", mbox.Flags)
+
+	// Get the last 4 messages
+	from := uint32(1)
+	to := mbox.Messages
+	if mbox.Messages > 3 {
+		// We're using unsigned integers here, only substract if the result is > 0
+		from = mbox.Messages - 3
+	}
+	seqset := new(imap.SeqSet)
+	seqset.AddRange(from, to)
+	items := []imap.FetchItem{imap.FetchEnvelope}
+
+	messages := make(chan *imap.Message, 10)
+	done = make(chan error, 1)
+	go func() {
+		done <- c.Fetch(seqset, items, messages)
+	}()
+
+	log.Println("Last 4 messages:")
+	for msg := range messages {
+		log.Println("* " + msg.Envelope.Subject)
+	}
+
+	if err := <-done; err != nil {
+		log.Fatal(err)
+	}
+
+	log.Println("Done!")
+}
+
+func ExampleClient_Fetch() {
+	// Let's assume c is a client
+	var c *client.Client
+
+	// Select INBOX
+	mbox, err := c.Select("INBOX", false)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Get the last message
+	if mbox.Messages == 0 {
+		log.Fatal("No message in mailbox")
+	}
+	seqset := new(imap.SeqSet)
+	seqset.AddRange(mbox.Messages, mbox.Messages)
+
+	// Get the whole message body
+	section := &imap.BodySectionName{}
+	items := []imap.FetchItem{section.FetchItem()}
+
+	messages := make(chan *imap.Message, 1)
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Fetch(seqset, items, messages)
+	}()
+
+	log.Println("Last message:")
+	msg := <-messages
+	r := msg.GetBody(section)
+	if r == nil {
+		log.Fatal("Server didn't returned message body")
+	}
+
+	if err := <-done; err != nil {
+		log.Fatal(err)
+	}
+
+	m, err := mail.ReadMessage(r)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	header := m.Header
+	log.Println("Date:", header.Get("Date"))
+	log.Println("From:", header.Get("From"))
+	log.Println("To:", header.Get("To"))
+	log.Println("Subject:", header.Get("Subject"))
+
+	body, err := ioutil.ReadAll(m.Body)
+	if err != nil {
+		log.Fatal(err)
+	}
+	log.Println(body)
+}
+
+func ExampleClient_Append() {
+	// Let's assume c is a client
+	var c *client.Client
+
+	// Write the message to a buffer
+	var b bytes.Buffer
+	b.WriteString("From: <root@nsa.gov>\r\n")
+	b.WriteString("To: <root@gchq.gov.uk>\r\n")
+	b.WriteString("Subject: Hey there\r\n")
+	b.WriteString("\r\n")
+	b.WriteString("Hey <3")
+
+	// Append it to INBOX, with two flags
+	flags := []string{imap.FlaggedFlag, "foobar"}
+	if err := c.Append("INBOX", flags, time.Now(), &b); err != nil {
+		log.Fatal(err)
+	}
+}
+
+func ExampleClient_Expunge() {
+	// Let's assume c is a client
+	var c *client.Client
+
+	// Select INBOX
+	mbox, err := c.Select("INBOX", false)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// We will delete the last message
+	if mbox.Messages == 0 {
+		log.Fatal("No message in mailbox")
+	}
+	seqset := new(imap.SeqSet)
+	seqset.AddNum(mbox.Messages)
+
+	// First mark the message as deleted
+	item := imap.FormatFlagsOp(imap.AddFlags, true)
+	flags := []interface{}{imap.DeletedFlag}
+	if err := c.Store(seqset, item, flags, nil); err != nil {
+		log.Fatal(err)
+	}
+
+	// Then delete it
+	if err := c.Expunge(nil); err != nil {
+		log.Fatal(err)
+	}
+
+	log.Println("Last message has been deleted")
+}
+
+func ExampleClient_StartTLS() {
+	log.Println("Connecting to server...")
+
+	// Connect to server
+	c, err := client.Dial("mail.example.org:143")
+	if err != nil {
+		log.Fatal(err)
+	}
+	log.Println("Connected")
+
+	// Don't forget to logout
+	defer c.Logout()
+
+	// Start a TLS session
+	tlsConfig := &tls.Config{ServerName: "mail.example.org"}
+	if err := c.StartTLS(tlsConfig); err != nil {
+		log.Fatal(err)
+	}
+	log.Println("TLS started")
+
+	// Now we can login
+	if err := c.Login("username", "password"); err != nil {
+		log.Fatal(err)
+	}
+	log.Println("Logged in")
+}
+
+func ExampleClient_Store() {
+	// Let's assume c is a client
+	var c *client.Client
+
+	// Select INBOX
+	_, err := c.Select("INBOX", false)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Mark message 42 as seen
+	seqSet := new(imap.SeqSet)
+	seqSet.AddNum(42)
+	item := imap.FormatFlagsOp(imap.AddFlags, true)
+	flags := []interface{}{imap.SeenFlag}
+	err = c.Store(seqSet, item, flags, nil)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	log.Println("Message has been marked as seen")
+}
+
+func ExampleClient_Search() {
+	// Let's assume c is a client
+	var c *client.Client
+
+	// Select INBOX
+	_, err := c.Select("INBOX", false)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Set search criteria
+	criteria := imap.NewSearchCriteria()
+	criteria.WithoutFlags = []string{imap.SeenFlag}
+	ids, err := c.Search(criteria)
+	if err != nil {
+		log.Fatal(err)
+	}
+	log.Println("IDs found:", ids)
+
+	if len(ids) > 0 {
+		seqset := new(imap.SeqSet)
+		seqset.AddNum(ids...)
+
+		messages := make(chan *imap.Message, 10)
+		done := make(chan error, 1)
+		go func() {
+			done <- c.Fetch(seqset, []imap.FetchItem{imap.FetchEnvelope}, messages)
+		}()
+
+		log.Println("Unseen messages:")
+		for msg := range messages {
+			log.Println("* " + msg.Envelope.Subject)
+		}
+
+		if err := <-done; err != nil {
+			log.Fatal(err)
+		}
+	}
+
+	log.Println("Done!")
+}
+
+func ExampleClient_Idle() {
+	// Let's assume c is a client
+	var c *client.Client
+
+	// Select a mailbox
+	if _, err := c.Select("INBOX", false); err != nil {
+		log.Fatal(err)
+	}
+
+	// Create a channel to receive mailbox updates
+	updates := make(chan client.Update)
+	c.Updates = updates
+
+	// Start idling
+	stopped := false
+	stop := make(chan struct{})
+	done := make(chan error, 1)
+	go func() {
+		done <- c.Idle(stop, nil)
+	}()
+
+	// Listen for updates
+	for {
+		select {
+		case update := <-updates:
+			log.Println("New update:", update)
+			if !stopped {
+				close(stop)
+				stopped = true
+			}
+		case err := <-done:
+			if err != nil {
+				log.Fatal(err)
+			}
+			log.Println("Not idling anymore")
+			return
+		}
+	}
+}

client/tag.go

@@ -0,0 +1,24 @@
+package client
+
+import (
+	"crypto/rand"
+	"encoding/base64"
+)
+
+func randomString(n int) (string, error) {
+	b := make([]byte, n)
+	_, err := rand.Read(b)
+	if err != nil {
+		return "", err
+	}
+
+	return base64.RawURLEncoding.EncodeToString(b), nil
+}
+
+func generateTag() string {
+	tag, err := randomString(4)
+	if err != nil {
+		panic(err)
+	}
+	return tag
+}

command.go

@@ -0,0 +1,57 @@
+package imap
+
+import (
+	"errors"
+	"strings"
+)
+
+// A value that can be converted to a command.
+type Commander interface {
+	Command() *Command
+}
+
+// A command.
+type Command struct {
+	// The command tag. It acts as a unique identifier for this command. If empty,
+	// the command is untagged.
+	Tag string
+	// The command name.
+	Name string
+	// The command arguments.
+	Arguments []interface{}
+}
+
+// Implements the Commander interface.
+func (cmd *Command) Command() *Command {
+	return cmd
+}
+
+func (cmd *Command) WriteTo(w *Writer) error {
+	tag := cmd.Tag
+	if tag == "" {
+		tag = "*"
+	}
+
+	fields := []interface{}{RawString(tag), RawString(cmd.Name)}
+	fields = append(fields, cmd.Arguments...)
+	return w.writeLine(fields...)
+}
+
+// Parse a command from fields.
+func (cmd *Command) Parse(fields []interface{}) error {
+	if len(fields) < 2 {
+		return errors.New("imap: cannot parse command: no enough fields")
+	}
+
+	var ok bool
+	if cmd.Tag, ok = fields[0].(string); !ok {
+		return errors.New("imap: cannot parse command: invalid tag")
+	}
+	if cmd.Name, ok = fields[1].(string); !ok {
+		return errors.New("imap: cannot parse command: invalid name")
+	}
+	cmd.Name = strings.ToUpper(cmd.Name) // Command names are case-insensitive
+
+	cmd.Arguments = fields[2:]
+	return nil
+}

command_test.go

@@ -0,0 +1,98 @@
+package imap_test
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/emersion/go-imap"
+)
+
+func TestCommand_Command(t *testing.T) {
+	cmd := &imap.Command{
+		Tag:  "A001",
+		Name: "NOOP",
+	}
+
+	if cmd.Command() != cmd {
+		t.Error("Command should return itself")
+	}
+}
+
+func TestCommand_WriteTo_NoArgs(t *testing.T) {
+	var b bytes.Buffer
+	w := imap.NewWriter(&b)
+
+	cmd := &imap.Command{
+		Tag:  "A001",
+		Name: "NOOP",
+	}
+
+	if err := cmd.WriteTo(w); err != nil {
+		t.Fatal(err)
+	}
+	if b.String() != "A001 NOOP\r\n" {
+		t.Fatal("Not the expected command: ", b.String())
+	}
+}
+
+func TestCommand_WriteTo_WithArgs(t *testing.T) {
+	var b bytes.Buffer
+	w := imap.NewWriter(&b)
+
+	cmd := &imap.Command{
+		Tag:       "A002",
+		Name:      "LOGIN",
+		Arguments: []interface{}{"username", "password"},
+	}
+
+	if err := cmd.WriteTo(w); err != nil {
+		t.Fatal(err)
+	}
+	if b.String() != "A002 LOGIN \"username\" \"password\"\r\n" {
+		t.Fatal("Not the expected command: ", b.String())
+	}
+}
+
+func TestCommand_Parse_NoArgs(t *testing.T) {
+	fields := []interface{}{"a", "NOOP"}
+
+	cmd := &imap.Command{}
+
+	if err := cmd.Parse(fields); err != nil {
+		t.Fatal(err)
+	}
+	if cmd.Tag != "a" {
+		t.Error("Invalid tag:", cmd.Tag)
+	}
+	if cmd.Name != "NOOP" {
+		t.Error("Invalid name:", cmd.Name)
+	}
+	if len(cmd.Arguments) != 0 {
+		t.Error("Invalid arguments:", cmd.Arguments)
+	}
+}
+
+func TestCommand_Parse_WithArgs(t *testing.T) {
+	fields := []interface{}{"a", "LOGIN", "username", "password"}
+
+	cmd := &imap.Command{}
+
+	if err := cmd.Parse(fields); err != nil {
+		t.Fatal(err)
+	}
+	if cmd.Tag != "a" {
+		t.Error("Invalid tag:", cmd.Tag)
+	}
+	if cmd.Name != "LOGIN" {
+		t.Error("Invalid name:", cmd.Name)
+	}
+	if len(cmd.Arguments) != 2 {
+		t.Error("Invalid arguments:", cmd.Arguments)
+	}
+	if username, ok := cmd.Arguments[0].(string); !ok || username != "username" {
+		t.Error("Invalid first argument:", cmd.Arguments[0])
+	}
+	if password, ok := cmd.Arguments[1].(string); !ok || password != "password" {
+		t.Error("Invalid second argument:", cmd.Arguments[1])
+	}
+}

commands/append.go

@@ -0,0 +1,93 @@
+package commands
+
+import (
+	"errors"
+	"time"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/utf7"
+)
+
+// Append is an APPEND command, as defined in RFC 3501 section 6.3.11.
+type Append struct {
+	Mailbox string
+	Flags   []string
+	Date    time.Time
+	Message imap.Literal
+}
+
+func (cmd *Append) Command() *imap.Command {
+	var args []interface{}
+
+	mailbox, _ := utf7.Encoding.NewEncoder().String(cmd.Mailbox)
+	args = append(args, imap.FormatMailboxName(mailbox))
+
+	if cmd.Flags != nil {
+		flags := make([]interface{}, len(cmd.Flags))
+		for i, flag := range cmd.Flags {
+			flags[i] = imap.RawString(flag)
+		}
+		args = append(args, flags)
+	}
+
+	if !cmd.Date.IsZero() {
+		args = append(args, cmd.Date)
+	}
+
+	args = append(args, cmd.Message)
+
+	return &imap.Command{
+		Name:      "APPEND",
+		Arguments: args,
+	}
+}
+
+func (cmd *Append) Parse(fields []interface{}) (err error) {
+	if len(fields) < 2 {
+		return errors.New("No enough arguments")
+	}
+
+	// Parse mailbox name
+	if mailbox, err := imap.ParseString(fields[0]); err != nil {
+		return err
+	} else if mailbox, err = utf7.Encoding.NewDecoder().String(mailbox); err != nil {
+		return err
+	} else {
+		cmd.Mailbox = imap.CanonicalMailboxName(mailbox)
+	}
+
+	// Parse message literal
+	litIndex := len(fields) - 1
+	var ok bool
+	if cmd.Message, ok = fields[litIndex].(imap.Literal); !ok {
+		return errors.New("Message must be a literal")
+	}
+
+	// Remaining fields a optional
+	fields = fields[1:litIndex]
+	if len(fields) > 0 {
+		// Parse flags list
+		if flags, ok := fields[0].([]interface{}); ok {
+			if cmd.Flags, err = imap.ParseStringList(flags); err != nil {
+				return err
+			}
+
+			for i, flag := range cmd.Flags {
+				cmd.Flags[i] = imap.CanonicalFlag(flag)
+			}
+
+			fields = fields[1:]
+		}
+
+		// Parse date
+		if len(fields) > 0 {
+			if date, ok := fields[0].(string); !ok {
+				return errors.New("Date must be a string")
+			} else if cmd.Date, err = time.Parse(imap.DateTimeLayout, date); err != nil {
+				return err
+			}
+		}
+	}
+
+	return
+}

commands/authenticate.go

@@ -0,0 +1,124 @@
+package commands
+
+import (
+	"bufio"
+	"encoding/base64"
+	"errors"
+	"io"
+	"strings"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-sasl"
+)
+
+// AuthenticateConn is a connection that supports IMAP authentication.
+type AuthenticateConn interface {
+	io.Reader
+
+	// WriteResp writes an IMAP response to this connection.
+	WriteResp(res imap.WriterTo) error
+}
+
+// Authenticate is an AUTHENTICATE command, as defined in RFC 3501 section
+// 6.2.2.
+type Authenticate struct {
+	Mechanism       string
+	InitialResponse []byte
+}
+
+func (cmd *Authenticate) Command() *imap.Command {
+	args := []interface{}{imap.RawString(cmd.Mechanism)}
+	if cmd.InitialResponse != nil {
+		var encodedResponse string
+		if len(cmd.InitialResponse) == 0 {
+			// Empty initial response should be encoded as "=", not empty
+			// string.
+			encodedResponse = "="
+		} else {
+			encodedResponse = base64.StdEncoding.EncodeToString(cmd.InitialResponse)
+		}
+
+		args = append(args, imap.RawString(encodedResponse))
+	}
+	return &imap.Command{
+		Name:      "AUTHENTICATE",
+		Arguments: args,
+	}
+}
+
+func (cmd *Authenticate) Parse(fields []interface{}) error {
+	if len(fields) < 1 {
+		return errors.New("Not enough arguments")
+	}
+
+	var ok bool
+	if cmd.Mechanism, ok = fields[0].(string); !ok {
+		return errors.New("Mechanism must be a string")
+	}
+	cmd.Mechanism = strings.ToUpper(cmd.Mechanism)
+
+	if len(fields) != 2 {
+		return nil
+	}
+
+	encodedResponse, ok := fields[1].(string)
+	if !ok {
+		return errors.New("Initial response must be a string")
+	}
+	if encodedResponse == "=" {
+		cmd.InitialResponse = []byte{}
+		return nil
+	}
+
+	var err error
+	cmd.InitialResponse, err = base64.StdEncoding.DecodeString(encodedResponse)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (cmd *Authenticate) Handle(mechanisms map[string]sasl.Server, conn AuthenticateConn) error {
+	sasl, ok := mechanisms[cmd.Mechanism]
+	if !ok {
+		return errors.New("Unsupported mechanism")
+	}
+
+	scanner := bufio.NewScanner(conn)
+
+	response := cmd.InitialResponse
+	for {
+		challenge, done, err := sasl.Next(response)
+		if err != nil || done {
+			return err
+		}
+
+		encoded := base64.StdEncoding.EncodeToString(challenge)
+		cont := &imap.ContinuationReq{Info: encoded}
+		if err := conn.WriteResp(cont); err != nil {
+			return err
+		}
+
+		if !scanner.Scan() {
+			if err := scanner.Err(); err != nil {
+				return err
+			}
+			return errors.New("unexpected EOF")
+		}
+
+		encoded = scanner.Text()
+		if encoded != "" {
+			if encoded == "*" {
+				return &imap.ErrStatusResp{Resp: &imap.StatusResp{
+					Type: imap.StatusRespBad,
+					Info: "negotiation cancelled",
+				}}
+			}
+			response, err = base64.StdEncoding.DecodeString(encoded)
+			if err != nil {
+				return err
+			}
+		}
+	}
+}

commands/capability.go

@@ -0,0 +1,18 @@
+package commands
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// Capability is a CAPABILITY command, as defined in RFC 3501 section 6.1.1.
+type Capability struct{}
+
+func (c *Capability) Command() *imap.Command {
+	return &imap.Command{
+		Name: "CAPABILITY",
+	}
+}
+
+func (c *Capability) Parse(fields []interface{}) error {
+	return nil
+}

commands/check.go

@@ -0,0 +1,18 @@
+package commands
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// Check is a CHECK command, as defined in RFC 3501 section 6.4.1.
+type Check struct{}
+
+func (cmd *Check) Command() *imap.Command {
+	return &imap.Command{
+		Name: "CHECK",
+	}
+}
+
+func (cmd *Check) Parse(fields []interface{}) error {
+	return nil
+}

commands/close.go

@@ -0,0 +1,18 @@
+package commands
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// Close is a CLOSE command, as defined in RFC 3501 section 6.4.2.
+type Close struct{}
+
+func (cmd *Close) Command() *imap.Command {
+	return &imap.Command{
+		Name: "CLOSE",
+	}
+}
+
+func (cmd *Close) Parse(fields []interface{}) error {
+	return nil
+}

commands/commands.go

@@ -0,0 +1,2 @@
+// Package commands implements IMAP commands defined in RFC 3501.
+package commands

commands/copy.go

@@ -0,0 +1,47 @@
+package commands
+
+import (
+	"errors"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/utf7"
+)
+
+// Copy is a COPY command, as defined in RFC 3501 section 6.4.7.
+type Copy struct {
+	SeqSet  *imap.SeqSet
+	Mailbox string
+}
+
+func (cmd *Copy) Command() *imap.Command {
+	mailbox, _ := utf7.Encoding.NewEncoder().String(cmd.Mailbox)
+
+	return &imap.Command{
+		Name:      "COPY",
+		Arguments: []interface{}{cmd.SeqSet, imap.FormatMailboxName(mailbox)},
+	}
+}
+
+func (cmd *Copy) Parse(fields []interface{}) error {
+	if len(fields) < 2 {
+		return errors.New("No enough arguments")
+	}
+
+	if seqSet, ok := fields[0].(string); !ok {
+		return errors.New("Invalid sequence set")
+	} else if seqSet, err := imap.ParseSeqSet(seqSet); err != nil {
+		return err
+	} else {
+		cmd.SeqSet = seqSet
+	}
+
+	if mailbox, err := imap.ParseString(fields[1]); err != nil {
+		return err
+	} else if mailbox, err := utf7.Encoding.NewDecoder().String(mailbox); err != nil {
+		return err
+	} else {
+		cmd.Mailbox = imap.CanonicalMailboxName(mailbox)
+	}
+
+	return nil
+}

commands/create.go

@@ -0,0 +1,38 @@
+package commands
+
+import (
+	"errors"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/utf7"
+)
+
+// Create is a CREATE command, as defined in RFC 3501 section 6.3.3.
+type Create struct {
+	Mailbox string
+}
+
+func (cmd *Create) Command() *imap.Command {
+	mailbox, _ := utf7.Encoding.NewEncoder().String(cmd.Mailbox)
+
+	return &imap.Command{
+		Name:      "CREATE",
+		Arguments: []interface{}{mailbox},
+	}
+}
+
+func (cmd *Create) Parse(fields []interface{}) error {
+	if len(fields) < 1 {
+		return errors.New("No enough arguments")
+	}
+
+	if mailbox, err := imap.ParseString(fields[0]); err != nil {
+		return err
+	} else if mailbox, err := utf7.Encoding.NewDecoder().String(mailbox); err != nil {
+		return err
+	} else {
+		cmd.Mailbox = imap.CanonicalMailboxName(mailbox)
+	}
+
+	return nil
+}

commands/delete.go

@@ -0,0 +1,38 @@
+package commands
+
+import (
+	"errors"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/utf7"
+)
+
+// Delete is a DELETE command, as defined in RFC 3501 section 6.3.3.
+type Delete struct {
+	Mailbox string
+}
+
+func (cmd *Delete) Command() *imap.Command {
+	mailbox, _ := utf7.Encoding.NewEncoder().String(cmd.Mailbox)
+
+	return &imap.Command{
+		Name:      "DELETE",
+		Arguments: []interface{}{imap.FormatMailboxName(mailbox)},
+	}
+}
+
+func (cmd *Delete) Parse(fields []interface{}) error {
+	if len(fields) < 1 {
+		return errors.New("No enough arguments")
+	}
+
+	if mailbox, err := imap.ParseString(fields[0]); err != nil {
+		return err
+	} else if mailbox, err := utf7.Encoding.NewDecoder().String(mailbox); err != nil {
+		return err
+	} else {
+		cmd.Mailbox = imap.CanonicalMailboxName(mailbox)
+	}
+
+	return nil
+}

commands/enable.go

@@ -0,0 +1,28 @@
+package commands
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// An ENABLE command, defined in RFC 5161 section 3.1.
+type Enable struct {
+	Caps []string
+}
+
+func (cmd *Enable) Command() *imap.Command {
+	args := make([]interface{}, len(cmd.Caps))
+	for i, c := range cmd.Caps {
+		args[i] = imap.RawString(c)
+	}
+
+	return &imap.Command{
+		Name:      "ENABLE",
+		Arguments: args,
+	}
+}
+
+func (cmd *Enable) Parse(fields []interface{}) error {
+	var err error
+	cmd.Caps, err = imap.ParseStringList(fields)
+	return err
+}

commands/expunge.go

@@ -0,0 +1,16 @@
+package commands
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// Expunge is an EXPUNGE command, as defined in RFC 3501 section 6.4.3.
+type Expunge struct{}
+
+func (cmd *Expunge) Command() *imap.Command {
+	return &imap.Command{Name: "EXPUNGE"}
+}
+
+func (cmd *Expunge) Parse(fields []interface{}) error {
+	return nil
+}

commands/fetch.go

@@ -0,0 +1,63 @@
+package commands
+
+import (
+	"errors"
+	"strings"
+
+	"github.com/emersion/go-imap"
+)
+
+// Fetch is a FETCH command, as defined in RFC 3501 section 6.4.5.
+type Fetch struct {
+	SeqSet *imap.SeqSet
+	Items  []imap.FetchItem
+}
+
+func (cmd *Fetch) Command() *imap.Command {
+	// Handle FETCH macros separately as they should not be serialized within parentheses
+	if len(cmd.Items) == 1 && (cmd.Items[0] == imap.FetchAll || cmd.Items[0] == imap.FetchFast || cmd.Items[0] == imap.FetchFull) {
+		return &imap.Command{
+			Name:      "FETCH",
+			Arguments: []interface{}{cmd.SeqSet, imap.RawString(cmd.Items[0])},
+		}
+	} else {
+		items := make([]interface{}, len(cmd.Items))
+		for i, item := range cmd.Items {
+			items[i] = imap.RawString(item)
+		}
+
+		return &imap.Command{
+			Name:      "FETCH",
+			Arguments: []interface{}{cmd.SeqSet, items},
+		}
+	}
+}
+
+func (cmd *Fetch) Parse(fields []interface{}) error {
+	if len(fields) < 2 {
+		return errors.New("No enough arguments")
+	}
+
+	var err error
+	if seqset, ok := fields[0].(string); !ok {
+		return errors.New("Sequence set must be an atom")
+	} else if cmd.SeqSet, err = imap.ParseSeqSet(seqset); err != nil {
+		return err
+	}
+
+	switch items := fields[1].(type) {
+	case string: // A macro or a single item
+		cmd.Items = imap.FetchItem(strings.ToUpper(items)).Expand()
+	case []interface{}: // A list of items
+		cmd.Items = make([]imap.FetchItem, 0, len(items))
+		for _, v := range items {
+			itemStr, _ := v.(string)
+			item := imap.FetchItem(strings.ToUpper(itemStr))
+			cmd.Items = append(cmd.Items, item.Expand()...)
+		}
+	default:
+		return errors.New("Items must be either a string or a list")
+	}
+
+	return nil
+}

commands/idle.go

@@ -0,0 +1,17 @@
+package commands
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// An IDLE command.
+// Se RFC 2177 section 3.
+type Idle struct{}
+
+func (cmd *Idle) Command() *imap.Command {
+	return &imap.Command{Name: "IDLE"}
+}
+
+func (cmd *Idle) Parse(fields []interface{}) error {
+	return nil
+}

commands/list.go

@@ -0,0 +1,60 @@
+package commands
+
+import (
+	"errors"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/utf7"
+)
+
+// List is a LIST command, as defined in RFC 3501 section 6.3.8. If Subscribed
+// is set to true, LSUB will be used instead.
+type List struct {
+	Reference string
+	Mailbox   string
+
+	Subscribed bool
+}
+
+func (cmd *List) Command() *imap.Command {
+	name := "LIST"
+	if cmd.Subscribed {
+		name = "LSUB"
+	}
+
+	enc := utf7.Encoding.NewEncoder()
+	ref, _ := enc.String(cmd.Reference)
+	mailbox, _ := enc.String(cmd.Mailbox)
+
+	return &imap.Command{
+		Name:      name,
+		Arguments: []interface{}{ref, mailbox},
+	}
+}
+
+func (cmd *List) Parse(fields []interface{}) error {
+	if len(fields) < 2 {
+		return errors.New("No enough arguments")
+	}
+
+	dec := utf7.Encoding.NewDecoder()
+
+	if mailbox, err := imap.ParseString(fields[0]); err != nil {
+		return err
+	} else if mailbox, err := dec.String(mailbox); err != nil {
+		return err
+	} else {
+		// TODO: canonical mailbox path
+		cmd.Reference = imap.CanonicalMailboxName(mailbox)
+	}
+
+	if mailbox, err := imap.ParseString(fields[1]); err != nil {
+		return err
+	} else if mailbox, err := dec.String(mailbox); err != nil {
+		return err
+	} else {
+		cmd.Mailbox = imap.CanonicalMailboxName(mailbox)
+	}
+
+	return nil
+}

commands/login.go

@@ -0,0 +1,36 @@
+package commands
+
+import (
+	"errors"
+
+	"github.com/emersion/go-imap"
+)
+
+// Login is a LOGIN command, as defined in RFC 3501 section 6.2.2.
+type Login struct {
+	Username string
+	Password string
+}
+
+func (cmd *Login) Command() *imap.Command {
+	return &imap.Command{
+		Name:      "LOGIN",
+		Arguments: []interface{}{cmd.Username, cmd.Password},
+	}
+}
+
+func (cmd *Login) Parse(fields []interface{}) error {
+	if len(fields) < 2 {
+		return errors.New("Not enough arguments")
+	}
+
+	var err error
+	if cmd.Username, err = imap.ParseString(fields[0]); err != nil {
+		return err
+	}
+	if cmd.Password, err = imap.ParseString(fields[1]); err != nil {
+		return err
+	}
+
+	return nil
+}

commands/logout.go

@@ -0,0 +1,18 @@
+package commands
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// Logout is a LOGOUT command, as defined in RFC 3501 section 6.1.3.
+type Logout struct{}
+
+func (c *Logout) Command() *imap.Command {
+	return &imap.Command{
+		Name: "LOGOUT",
+	}
+}
+
+func (c *Logout) Parse(fields []interface{}) error {
+	return nil
+}

commands/move.go

@@ -0,0 +1,48 @@
+package commands
+
+import (
+	"errors"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/utf7"
+)
+
+// A MOVE command.
+// See RFC 6851 section 3.1.
+type Move struct {
+	SeqSet  *imap.SeqSet
+	Mailbox string
+}
+
+func (cmd *Move) Command() *imap.Command {
+	mailbox, _ := utf7.Encoding.NewEncoder().String(cmd.Mailbox)
+
+	return &imap.Command{
+		Name:      "MOVE",
+		Arguments: []interface{}{cmd.SeqSet, mailbox},
+	}
+}
+
+func (cmd *Move) Parse(fields []interface{}) (err error) {
+	if len(fields) < 2 {
+		return errors.New("No enough arguments")
+	}
+
+	seqset, ok := fields[0].(string)
+	if !ok {
+		return errors.New("Invalid sequence set")
+	}
+	if cmd.SeqSet, err = imap.ParseSeqSet(seqset); err != nil {
+		return err
+	}
+
+	mailbox, ok := fields[1].(string)
+	if !ok {
+		return errors.New("Mailbox name must be a string")
+	}
+	if cmd.Mailbox, err = utf7.Encoding.NewDecoder().String(mailbox); err != nil {
+		return err
+	}
+
+	return
+}

commands/noop.go

@@ -0,0 +1,18 @@
+package commands
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// Noop is a NOOP command, as defined in RFC 3501 section 6.1.2.
+type Noop struct{}
+
+func (c *Noop) Command() *imap.Command {
+	return &imap.Command{
+		Name: "NOOP",
+	}
+}
+
+func (c *Noop) Parse(fields []interface{}) error {
+	return nil
+}

commands/rename.go

@@ -0,0 +1,51 @@
+package commands
+
+import (
+	"errors"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/utf7"
+)
+
+// Rename is a RENAME command, as defined in RFC 3501 section 6.3.5.
+type Rename struct {
+	Existing string
+	New      string
+}
+
+func (cmd *Rename) Command() *imap.Command {
+	enc := utf7.Encoding.NewEncoder()
+	existingName, _ := enc.String(cmd.Existing)
+	newName, _ := enc.String(cmd.New)
+
+	return &imap.Command{
+		Name:      "RENAME",
+		Arguments: []interface{}{imap.FormatMailboxName(existingName), imap.FormatMailboxName(newName)},
+	}
+}
+
+func (cmd *Rename) Parse(fields []interface{}) error {
+	if len(fields) < 2 {
+		return errors.New("No enough arguments")
+	}
+
+	dec := utf7.Encoding.NewDecoder()
+
+	if existingName, err := imap.ParseString(fields[0]); err != nil {
+		return err
+	} else if existingName, err := dec.String(existingName); err != nil {
+		return err
+	} else {
+		cmd.Existing = imap.CanonicalMailboxName(existingName)
+	}
+
+	if newName, err := imap.ParseString(fields[1]); err != nil {
+		return err
+	} else if newName, err := dec.String(newName); err != nil {
+		return err
+	} else {
+		cmd.New = imap.CanonicalMailboxName(newName)
+	}
+
+	return nil
+}

commands/search.go

@@ -0,0 +1,57 @@
+package commands
+
+import (
+	"errors"
+	"io"
+	"strings"
+
+	"github.com/emersion/go-imap"
+)
+
+// Search is a SEARCH command, as defined in RFC 3501 section 6.4.4.
+type Search struct {
+	Charset  string
+	Criteria *imap.SearchCriteria
+}
+
+func (cmd *Search) Command() *imap.Command {
+	var args []interface{}
+	if cmd.Charset != "" {
+		args = append(args, imap.RawString("CHARSET"), imap.RawString(cmd.Charset))
+	}
+	args = append(args, cmd.Criteria.Format()...)
+
+	return &imap.Command{
+		Name:      "SEARCH",
+		Arguments: args,
+	}
+}
+
+func (cmd *Search) Parse(fields []interface{}) error {
+	if len(fields) == 0 {
+		return errors.New("Missing search criteria")
+	}
+
+	// Parse charset
+	if f, ok := fields[0].(string); ok && strings.EqualFold(f, "CHARSET") {
+		if len(fields) < 2 {
+			return errors.New("Missing CHARSET value")
+		}
+		if cmd.Charset, ok = fields[1].(string); !ok {
+			return errors.New("Charset must be a string")
+		}
+		fields = fields[2:]
+	}
+
+	var charsetReader func(io.Reader) io.Reader
+	charset := strings.ToLower(cmd.Charset)
+	if charset != "utf-8" && charset != "us-ascii" && charset != "" {
+		charsetReader = func(r io.Reader) io.Reader {
+			r, _ = imap.CharsetReader(charset, r)
+			return r
+		}
+	}
+
+	cmd.Criteria = new(imap.SearchCriteria)
+	return cmd.Criteria.ParseWithCharset(fields, charsetReader)
+}

commands/select.go

@@ -0,0 +1,45 @@
+package commands
+
+import (
+	"errors"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/utf7"
+)
+
+// Select is a SELECT command, as defined in RFC 3501 section 6.3.1. If ReadOnly
+// is set to true, the EXAMINE command will be used instead.
+type Select struct {
+	Mailbox  string
+	ReadOnly bool
+}
+
+func (cmd *Select) Command() *imap.Command {
+	name := "SELECT"
+	if cmd.ReadOnly {
+		name = "EXAMINE"
+	}
+
+	mailbox, _ := utf7.Encoding.NewEncoder().String(cmd.Mailbox)
+
+	return &imap.Command{
+		Name:      name,
+		Arguments: []interface{}{imap.FormatMailboxName(mailbox)},
+	}
+}
+
+func (cmd *Select) Parse(fields []interface{}) error {
+	if len(fields) < 1 {
+		return errors.New("No enough arguments")
+	}
+
+	if mailbox, err := imap.ParseString(fields[0]); err != nil {
+		return err
+	} else if mailbox, err := utf7.Encoding.NewDecoder().String(mailbox); err != nil {
+		return err
+	} else {
+		cmd.Mailbox = imap.CanonicalMailboxName(mailbox)
+	}
+
+	return nil
+}

commands/starttls.go

@@ -0,0 +1,18 @@
+package commands
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// StartTLS is a STARTTLS command, as defined in RFC 3501 section 6.2.1.
+type StartTLS struct{}
+
+func (cmd *StartTLS) Command() *imap.Command {
+	return &imap.Command{
+		Name: "STARTTLS",
+	}
+}
+
+func (cmd *StartTLS) Parse(fields []interface{}) error {
+	return nil
+}

commands/status.go

@@ -0,0 +1,58 @@
+package commands
+
+import (
+	"errors"
+	"strings"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/utf7"
+)
+
+// Status is a STATUS command, as defined in RFC 3501 section 6.3.10.
+type Status struct {
+	Mailbox string
+	Items   []imap.StatusItem
+}
+
+func (cmd *Status) Command() *imap.Command {
+	mailbox, _ := utf7.Encoding.NewEncoder().String(cmd.Mailbox)
+
+	items := make([]interface{}, len(cmd.Items))
+	for i, item := range cmd.Items {
+		items[i] = imap.RawString(item)
+	}
+
+	return &imap.Command{
+		Name:      "STATUS",
+		Arguments: []interface{}{imap.FormatMailboxName(mailbox), items},
+	}
+}
+
+func (cmd *Status) Parse(fields []interface{}) error {
+	if len(fields) < 2 {
+		return errors.New("No enough arguments")
+	}
+
+	if mailbox, err := imap.ParseString(fields[0]); err != nil {
+		return err
+	} else if mailbox, err := utf7.Encoding.NewDecoder().String(mailbox); err != nil {
+		return err
+	} else {
+		cmd.Mailbox = imap.CanonicalMailboxName(mailbox)
+	}
+
+	items, ok := fields[1].([]interface{})
+	if !ok {
+		return errors.New("STATUS command parameter is not a list")
+	}
+	cmd.Items = make([]imap.StatusItem, len(items))
+	for i, f := range items {
+		if s, ok := f.(string); !ok {
+			return errors.New("Got a non-string field in a STATUS command parameter")
+		} else {
+			cmd.Items[i] = imap.StatusItem(strings.ToUpper(s))
+		}
+	}
+
+	return nil
+}

commands/store.go

@@ -0,0 +1,50 @@
+package commands
+
+import (
+	"errors"
+	"strings"
+
+	"github.com/emersion/go-imap"
+)
+
+// Store is a STORE command, as defined in RFC 3501 section 6.4.6.
+type Store struct {
+	SeqSet *imap.SeqSet
+	Item   imap.StoreItem
+	Value  interface{}
+}
+
+func (cmd *Store) Command() *imap.Command {
+	return &imap.Command{
+		Name:      "STORE",
+		Arguments: []interface{}{cmd.SeqSet, imap.RawString(cmd.Item), cmd.Value},
+	}
+}
+
+func (cmd *Store) Parse(fields []interface{}) error {
+	if len(fields) < 3 {
+		return errors.New("No enough arguments")
+	}
+
+	seqset, ok := fields[0].(string)
+	if !ok {
+		return errors.New("Invalid sequence set")
+	}
+	var err error
+	if cmd.SeqSet, err = imap.ParseSeqSet(seqset); err != nil {
+		return err
+	}
+
+	if item, ok := fields[1].(string); !ok {
+		return errors.New("Item name must be a string")
+	} else {
+		cmd.Item = imap.StoreItem(strings.ToUpper(item))
+	}
+
+	if len(fields[2:]) == 1 {
+		cmd.Value = fields[2]
+	} else {
+		cmd.Value = fields[2:]
+	}
+	return nil
+}

commands/subscribe.go

@@ -0,0 +1,63 @@
+package commands
+
+import (
+	"errors"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/utf7"
+)
+
+// Subscribe is a SUBSCRIBE command, as defined in RFC 3501 section 6.3.6.
+type Subscribe struct {
+	Mailbox string
+}
+
+func (cmd *Subscribe) Command() *imap.Command {
+	mailbox, _ := utf7.Encoding.NewEncoder().String(cmd.Mailbox)
+
+	return &imap.Command{
+		Name:      "SUBSCRIBE",
+		Arguments: []interface{}{imap.FormatMailboxName(mailbox)},
+	}
+}
+
+func (cmd *Subscribe) Parse(fields []interface{}) error {
+	if len(fields) < 1 {
+		return errors.New("No enough arguments")
+	}
+
+	if mailbox, err := imap.ParseString(fields[0]); err != nil {
+		return err
+	} else if cmd.Mailbox, err = utf7.Encoding.NewDecoder().String(mailbox); err != nil {
+		return err
+	}
+	return nil
+}
+
+// An UNSUBSCRIBE command.
+// See RFC 3501 section 6.3.7
+type Unsubscribe struct {
+	Mailbox string
+}
+
+func (cmd *Unsubscribe) Command() *imap.Command {
+	mailbox, _ := utf7.Encoding.NewEncoder().String(cmd.Mailbox)
+
+	return &imap.Command{
+		Name:      "UNSUBSCRIBE",
+		Arguments: []interface{}{imap.FormatMailboxName(mailbox)},
+	}
+}
+
+func (cmd *Unsubscribe) Parse(fields []interface{}) error {
+	if len(fields) < 1 {
+		return errors.New("No enogh arguments")
+	}
+
+	if mailbox, err := imap.ParseString(fields[0]); err != nil {
+		return err
+	} else if cmd.Mailbox, err = utf7.Encoding.NewDecoder().String(mailbox); err != nil {
+		return err
+	}
+	return nil
+}

commands/uid.go

@@ -0,0 +1,44 @@
+package commands
+
+import (
+	"errors"
+	"strings"
+
+	"github.com/emersion/go-imap"
+)
+
+// Uid is a UID command, as defined in RFC 3501 section 6.4.8. It wraps another
+// command (e.g. wrapping a Fetch command will result in a UID FETCH).
+type Uid struct {
+	Cmd imap.Commander
+}
+
+func (cmd *Uid) Command() *imap.Command {
+	inner := cmd.Cmd.Command()
+
+	args := []interface{}{imap.RawString(inner.Name)}
+	args = append(args, inner.Arguments...)
+
+	return &imap.Command{
+		Name:      "UID",
+		Arguments: args,
+	}
+}
+
+func (cmd *Uid) Parse(fields []interface{}) error {
+	if len(fields) < 1 {
+		return errors.New("No command name specified")
+	}
+
+	name, ok := fields[0].(string)
+	if !ok {
+		return errors.New("Command name must be a string")
+	}
+
+	cmd.Cmd = &imap.Command{
+		Name:      strings.ToUpper(name), // Command names are case-insensitive
+		Arguments: fields[1:],
+	}
+
+	return nil
+}

commands/unselect.go

@@ -0,0 +1,17 @@
+package commands
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// An UNSELECT command.
+// See RFC 3691 section 2.
+type Unselect struct{}
+
+func (cmd *Unselect) Command() *imap.Command {
+	return &imap.Command{Name: "UNSELECT"}
+}
+
+func (cmd *Unselect) Parse(fields []interface{}) error {
+	return nil
+}

conn.go

@@ -0,0 +1,284 @@
+package imap
+
+import (
+	"bufio"
+	"crypto/tls"
+	"io"
+	"net"
+	"sync"
+)
+
+// A connection state.
+// See RFC 3501 section 3.
+type ConnState int
+
+const (
+	// In the connecting state, the server has not yet sent a greeting and no
+	// command can be issued.
+	ConnectingState = 0
+
+	// In the not authenticated state, the client MUST supply
+	// authentication credentials before most commands will be
+	// permitted.  This state is entered when a connection starts
+	// unless the connection has been pre-authenticated.
+	NotAuthenticatedState ConnState = 1 << 0
+
+	// In the authenticated state, the client is authenticated and MUST
+	// select a mailbox to access before commands that affect messages
+	// will be permitted.  This state is entered when a
+	// pre-authenticated connection starts, when acceptable
+	// authentication credentials have been provided, after an error in
+	// selecting a mailbox, or after a successful CLOSE command.
+	AuthenticatedState = 1 << 1
+
+	// In a selected state, a mailbox has been selected to access.
+	// This state is entered when a mailbox has been successfully
+	// selected.
+	SelectedState = AuthenticatedState + 1<<2
+
+	// In the logout state, the connection is being terminated. This
+	// state can be entered as a result of a client request (via the
+	// LOGOUT command) or by unilateral action on the part of either
+	// the client or server.
+	LogoutState = 1 << 3
+
+	// ConnectedState is either NotAuthenticatedState, AuthenticatedState or
+	// SelectedState.
+	ConnectedState = NotAuthenticatedState | AuthenticatedState | SelectedState
+)
+
+// A function that upgrades a connection.
+//
+// This should only be used by libraries implementing an IMAP extension (e.g.
+// COMPRESS).
+type ConnUpgrader func(conn net.Conn) (net.Conn, error)
+
+type Waiter struct {
+	start    sync.WaitGroup
+	end      sync.WaitGroup
+	finished bool
+}
+
+func NewWaiter() *Waiter {
+	w := &Waiter{finished: false}
+	w.start.Add(1)
+	w.end.Add(1)
+	return w
+}
+
+func (w *Waiter) Wait() {
+	if !w.finished {
+		// Signal that we are ready for upgrade to continue.
+		w.start.Done()
+		// Wait for upgrade to finish.
+		w.end.Wait()
+		w.finished = true
+	}
+}
+
+func (w *Waiter) WaitReady() {
+	if !w.finished {
+		// Wait for reader/writer goroutine to be ready for upgrade.
+		w.start.Wait()
+	}
+}
+
+func (w *Waiter) Close() {
+	if !w.finished {
+		// Upgrade is finished, close chanel to release reader/writer
+		w.end.Done()
+	}
+}
+
+type LockedWriter struct {
+	lock   sync.Mutex
+	writer io.Writer
+}
+
+// NewLockedWriter - goroutine safe writer.
+func NewLockedWriter(w io.Writer) io.Writer {
+	return &LockedWriter{writer: w}
+}
+
+func (w *LockedWriter) Write(b []byte) (int, error) {
+	w.lock.Lock()
+	defer w.lock.Unlock()
+	return w.writer.Write(b)
+}
+
+type debugWriter struct {
+	io.Writer
+
+	local  io.Writer
+	remote io.Writer
+}
+
+// NewDebugWriter creates a new io.Writer that will write local network activity
+// to local and remote network activity to remote.
+func NewDebugWriter(local, remote io.Writer) io.Writer {
+	return &debugWriter{Writer: local, local: local, remote: remote}
+}
+
+type multiFlusher struct {
+	flushers []flusher
+}
+
+func (mf *multiFlusher) Flush() error {
+	for _, f := range mf.flushers {
+		if err := f.Flush(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func newMultiFlusher(flushers ...flusher) flusher {
+	return &multiFlusher{flushers}
+}
+
+// Underlying connection state information.
+type ConnInfo struct {
+	RemoteAddr net.Addr
+	LocalAddr  net.Addr
+
+	// nil if connection is not using TLS.
+	TLS *tls.ConnectionState
+}
+
+// An IMAP connection.
+type Conn struct {
+	net.Conn
+	*Reader
+	*Writer
+
+	br *bufio.Reader
+	bw *bufio.Writer
+
+	waiter *Waiter
+
+	// Print all commands and responses to this io.Writer.
+	debug io.Writer
+}
+
+// NewConn creates a new IMAP connection.
+func NewConn(conn net.Conn, r *Reader, w *Writer) *Conn {
+	c := &Conn{Conn: conn, Reader: r, Writer: w}
+
+	c.init()
+	return c
+}
+
+func (c *Conn) createWaiter() *Waiter {
+	// create new waiter each time.
+	w := NewWaiter()
+	c.waiter = w
+	return w
+}
+
+func (c *Conn) init() {
+	r := io.Reader(c.Conn)
+	w := io.Writer(c.Conn)
+
+	if c.debug != nil {
+		localDebug, remoteDebug := c.debug, c.debug
+		if debug, ok := c.debug.(*debugWriter); ok {
+			localDebug, remoteDebug = debug.local, debug.remote
+		}
+		// If local and remote are the same, then we need a LockedWriter.
+		if localDebug == remoteDebug {
+			localDebug = NewLockedWriter(localDebug)
+			remoteDebug = localDebug
+		}
+
+		if localDebug != nil {
+			w = io.MultiWriter(c.Conn, localDebug)
+		}
+		if remoteDebug != nil {
+			r = io.TeeReader(c.Conn, remoteDebug)
+		}
+	}
+
+	if c.br == nil {
+		c.br = bufio.NewReader(r)
+		c.Reader.reader = c.br
+	} else {
+		c.br.Reset(r)
+	}
+
+	if c.bw == nil {
+		c.bw = bufio.NewWriter(w)
+		c.Writer.Writer = c.bw
+	} else {
+		c.bw.Reset(w)
+	}
+
+	if f, ok := c.Conn.(flusher); ok {
+		c.Writer.Writer = struct {
+			io.Writer
+			flusher
+		}{
+			c.bw,
+			newMultiFlusher(c.bw, f),
+		}
+	}
+}
+
+func (c *Conn) Info() *ConnInfo {
+	info := &ConnInfo{
+		RemoteAddr: c.RemoteAddr(),
+		LocalAddr:  c.LocalAddr(),
+	}
+
+	tlsConn, ok := c.Conn.(*tls.Conn)
+	if ok {
+		state := tlsConn.ConnectionState()
+		info.TLS = &state
+	}
+
+	return info
+}
+
+// Write implements io.Writer.
+func (c *Conn) Write(b []byte) (n int, err error) {
+	return c.Writer.Write(b)
+}
+
+// Flush writes any buffered data to the underlying connection.
+func (c *Conn) Flush() error {
+	return c.Writer.Flush()
+}
+
+// Upgrade a connection, e.g. wrap an unencrypted connection with an encrypted
+// tunnel.
+func (c *Conn) Upgrade(upgrader ConnUpgrader) error {
+	// Block reads and writes during the upgrading process
+	w := c.createWaiter()
+	defer w.Close()
+
+	upgraded, err := upgrader(c.Conn)
+	if err != nil {
+		return err
+	}
+
+	c.Conn = upgraded
+	c.init()
+	return nil
+}
+
+// Called by reader/writer goroutines to wait for Upgrade to finish
+func (c *Conn) Wait() {
+	c.waiter.Wait()
+}
+
+// Called by Upgrader to wait for reader/writer goroutines to be ready for
+// upgrade.
+func (c *Conn) WaitReady() {
+	c.waiter.WaitReady()
+}
+
+// SetDebug defines an io.Writer to which all network activity will be logged.
+// If nil is provided, network activity will not be logged.
+func (c *Conn) SetDebug(w io.Writer) {
+	c.debug = w
+	c.init()
+}

conn_test.go

@@ -0,0 +1,107 @@
+package imap_test
+
+import (
+	"bytes"
+	"io"
+	"net"
+	"testing"
+
+	"github.com/emersion/go-imap"
+)
+
+func TestNewConn(t *testing.T) {
+	b := &bytes.Buffer{}
+	c, s := net.Pipe()
+
+	done := make(chan error)
+	go (func() {
+		_, err := io.Copy(b, s)
+		done <- err
+	})()
+
+	r := imap.NewReader(nil)
+	w := imap.NewWriter(nil)
+
+	ic := imap.NewConn(c, r, w)
+
+	sent := []byte("hi")
+	ic.Write(sent)
+	ic.Flush()
+	ic.Close()
+
+	if err := <-done; err != nil {
+		t.Fatal(err)
+	}
+
+	s.Close()
+
+	received := b.Bytes()
+	if string(sent) != string(received) {
+		t.Errorf("Sent %v but received %v", sent, received)
+	}
+}
+
+func transform(b []byte) []byte {
+	bb := make([]byte, len(b))
+
+	for i, c := range b {
+		if rune(c) == 'c' {
+			bb[i] = byte('d')
+		} else {
+			bb[i] = c
+		}
+	}
+
+	return bb
+}
+
+type upgraded struct {
+	net.Conn
+}
+
+func (c *upgraded) Write(b []byte) (int, error) {
+	return c.Conn.Write(transform(b))
+}
+
+func TestConn_Upgrade(t *testing.T) {
+	b := &bytes.Buffer{}
+	c, s := net.Pipe()
+
+	done := make(chan error)
+	go (func() {
+		_, err := io.Copy(b, s)
+		done <- err
+	})()
+
+	r := imap.NewReader(nil)
+	w := imap.NewWriter(nil)
+
+	ic := imap.NewConn(c, r, w)
+
+	began := make(chan struct{})
+	go ic.Upgrade(func(conn net.Conn) (net.Conn, error) {
+		began <- struct{}{}
+		ic.WaitReady()
+		return &upgraded{conn}, nil
+	})
+	<-began
+
+	ic.Wait()
+
+	sent := []byte("abcd")
+	expected := transform(sent)
+	ic.Write(sent)
+	ic.Flush()
+	ic.Close()
+
+	if err := <-done; err != nil {
+		t.Fatal(err)
+	}
+
+	s.Close()
+
+	received := b.Bytes()
+	if string(expected) != string(received) {
+		t.Errorf("Expected %v but received %v", expected, received)
+	}
+}

date.go

@@ -0,0 +1,71 @@
+package imap
+
+import (
+	"fmt"
+	"regexp"
+	"time"
+)
+
+// Date and time layouts.
+// Dovecot adds a leading zero to dates:
+//   https://github.com/dovecot/core/blob/4fbd5c5e113078e72f29465ccc96d44955ceadc2/src/lib-imap/imap-date.c#L166
+// Cyrus adds a leading space to dates:
+//   https://github.com/cyrusimap/cyrus-imapd/blob/1cb805a3bffbdf829df0964f3b802cdc917e76db/lib/times.c#L543
+// GMail doesn't support leading spaces in dates used in SEARCH commands.
+const (
+	// Defined in RFC 3501 as date-text on page 83.
+	DateLayout = "_2-Jan-2006"
+	// Defined in RFC 3501 as date-time on page 83.
+	DateTimeLayout = "_2-Jan-2006 15:04:05 -0700"
+	// Defined in RFC 5322 section 3.3, mentioned as env-date in RFC 3501 page 84.
+	envelopeDateTimeLayout = "Mon, 02 Jan 2006 15:04:05 -0700"
+	// Use as an example in RFC 3501 page 54.
+	searchDateLayout = "2-Jan-2006"
+)
+
+// time.Time with a specific layout.
+type (
+	Date             time.Time
+	DateTime         time.Time
+	envelopeDateTime time.Time
+	searchDate       time.Time
+)
+
+// Permutations of the layouts defined in RFC 5322, section 3.3.
+var envelopeDateTimeLayouts = [...]string{
+	envelopeDateTimeLayout, // popular, try it first
+	"_2 Jan 2006 15:04:05 -0700",
+	"_2 Jan 2006 15:04:05 MST",
+	"_2 Jan 2006 15:04 -0700",
+	"_2 Jan 2006 15:04 MST",
+	"_2 Jan 06 15:04:05 -0700",
+	"_2 Jan 06 15:04:05 MST",
+	"_2 Jan 06 15:04 -0700",
+	"_2 Jan 06 15:04 MST",
+	"Mon, _2 Jan 2006 15:04:05 -0700",
+	"Mon, _2 Jan 2006 15:04:05 MST",
+	"Mon, _2 Jan 2006 15:04 -0700",
+	"Mon, _2 Jan 2006 15:04 MST",
+	"Mon, _2 Jan 06 15:04:05 -0700",
+	"Mon, _2 Jan 06 15:04:05 MST",
+	"Mon, _2 Jan 06 15:04 -0700",
+	"Mon, _2 Jan 06 15:04 MST",
+}
+
+// TODO: this is a blunt way to strip any trailing CFWS (comment). A sharper
+// one would strip multiple CFWS, and only if really valid according to
+// RFC5322.
+var commentRE = regexp.MustCompile(`[ \t]+\(.*\)$`)
+
+// Try parsing the date based on the layouts defined in RFC 5322, section 3.3.
+// Inspired by https://github.com/golang/go/blob/master/src/net/mail/message.go
+func parseMessageDateTime(maybeDate string) (time.Time, error) {
+	maybeDate = commentRE.ReplaceAllString(maybeDate, "")
+	for _, layout := range envelopeDateTimeLayouts {
+		parsed, err := time.Parse(layout, maybeDate)
+		if err == nil {
+			return parsed, nil
+		}
+	}
+	return time.Time{}, fmt.Errorf("date %s could not be parsed", maybeDate)
+}

date_test.go

@@ -0,0 +1,95 @@
+package imap
+
+import (
+	"testing"
+	"time"
+)
+
+var expectedDateTime = time.Date(2009, time.November, 2, 23, 0, 0, 0, time.FixedZone("", -6*60*60))
+var expectedDate = time.Date(2009, time.November, 2, 0, 0, 0, 0, time.FixedZone("", 0))
+
+func TestParseMessageDateTime(t *testing.T) {
+	tests := []struct {
+		in  string
+		out time.Time
+		ok  bool
+	}{
+		// some permutations
+		{"2 Nov 2009 23:00 -0600", expectedDateTime, true},
+		{"Tue, 2 Nov 2009 23:00:00 -0600", expectedDateTime, true},
+		{"Tue, 2 Nov 2009 23:00:00 -0600 (MST)", expectedDateTime, true},
+
+		// whitespace
+		{" 2 Nov 2009 23:00 -0600", expectedDateTime, true},
+		{"Tue,  2 Nov 2009 23:00:00 -0600", expectedDateTime, true},
+		{"Tue,  2 Nov 2009 23:00:00 -0600 (MST)", expectedDateTime, true},
+
+		// invalid
+		{"abc10 Nov 2009 23:00 -0600123", expectedDateTime, false},
+		{"10.Nov.2009 11:00:00 -9900", expectedDateTime, false},
+	}
+	for _, test := range tests {
+		out, err := parseMessageDateTime(test.in)
+		if !test.ok {
+			if err == nil {
+				t.Errorf("ParseMessageDateTime(%q) expected error; got %q", test.in, out)
+			}
+		} else if err != nil {
+			t.Errorf("ParseMessageDateTime(%q) expected %q; got %v", test.in, test.out, err)
+		} else if !out.Equal(test.out) {
+			t.Errorf("ParseMessageDateTime(%q) expected %q; got %q", test.in, test.out, out)
+		}
+	}
+}
+
+func TestParseDateTime(t *testing.T) {
+	tests := []struct {
+		in  string
+		out time.Time
+		ok  bool
+	}{
+		{"2-Nov-2009 23:00:00 -0600", expectedDateTime, true},
+
+		// whitespace
+		{" 2-Nov-2009 23:00:00 -0600", expectedDateTime, true},
+
+		// invalid or incorrect
+		{"10-Nov-2009", time.Time{}, false},
+		{"abc10-Nov-2009 23:00:00 -0600123", time.Time{}, false},
+	}
+	for _, test := range tests {
+		out, err := time.Parse(DateTimeLayout, test.in)
+		if !test.ok {
+			if err == nil {
+				t.Errorf("ParseDateTime(%q) expected error; got %q", test.in, out)
+			}
+		} else if err != nil {
+			t.Errorf("ParseDateTime(%q) expected %q; got %v", test.in, test.out, err)
+		} else if !out.Equal(test.out) {
+			t.Errorf("ParseDateTime(%q) expected %q; got %q", test.in, test.out, out)
+		}
+	}
+}
+
+func TestParseDate(t *testing.T) {
+	tests := []struct {
+		in  string
+		out time.Time
+		ok  bool
+	}{
+		{"2-Nov-2009", expectedDate, true},
+		{" 2-Nov-2009", expectedDate, true},
+	}
+	for _, test := range tests {
+		out, err := time.Parse(DateLayout, test.in)
+		if !test.ok {
+			if err == nil {
+				t.Errorf("ParseDate(%q) expected error; got %q", test.in, out)
+			}
+		} else if err != nil {
+			t.Errorf("ParseDate(%q) expected %q; got %v", test.in, test.out, err)
+		} else if !out.Equal(test.out) {
+			t.Errorf("ParseDate(%q) expected %q; got %q", test.in, test.out, out)
+		}
+	}
+}

go.mod

@@ -1,8 +1,9 @@
-module github.com/emersion/go-imap/v2
+module github.com/emersion/go-imap
 
-go 1.18
+go 1.13
 
 require (
-	github.com/emersion/go-message v0.18.1
-	github.com/emersion/go-sasl v0.0.0-20231106173351-e73c9f7bad43
+	github.com/emersion/go-message v0.15.0
+	github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21
+	golang.org/x/text v0.3.7
 )

go.sum

@@ -1,35 +1,10 @@
-github.com/emersion/go-message v0.18.1 h1:tfTxIoXFSFRwWaZsgnqS1DSZuGpYGzSmCZD8SK3QA2E=
-github.com/emersion/go-message v0.18.1/go.mod h1:XpJyL70LwRvq2a8rVbHXikPgKj8+aI0kGdHlg16ibYA=
-github.com/emersion/go-sasl v0.0.0-20231106173351-e73c9f7bad43 h1:hH4PQfOndHDlpzYfLAAfl63E8Le6F2+EL/cdhlkyRJY=
-github.com/emersion/go-sasl v0.0.0-20231106173351-e73c9f7bad43/go.mod h1:iL2twTeMvZnrg54ZoPDNfJaJaqy0xIQFuBdrLsmspwQ=
-github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
-golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
-golang.org/x/mod v0.8.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
-golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
-golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
-golang.org/x/net v0.6.0/go.mod h1:2Tu9+aMcznHK/AK1HMvgo6xiTLG5rD5rZLDS+rp2Bjs=
-golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20220722155255-886fb9371eb4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220722155257-8c9f86f7a55f/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.5.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
-golang.org/x/term v0.0.0-20210927222741-03fcf44c2211/go.mod h1:jbD1KX2456YbFQfuXm/mYQcufACuNUgVhRMnK/tPxf8=
-golang.org/x/term v0.5.0/go.mod h1:jMB1sMXY+tzblOD4FWmEbocvup2/aLOaQEp7JmGp78k=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+github.com/emersion/go-message v0.15.0 h1:urgKGqt2JAc9NFJcgncQcohHdiYb803YTH9OQwHBHIY=
+github.com/emersion/go-message v0.15.0/go.mod h1:wQUEfE+38+7EW8p8aZ96ptg6bAb1iwdgej19uXASlE4=
+github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21 h1:OJyUGMJTzHTd1XQp98QTaHernxMYzRaOasRir9hUlFQ=
+github.com/emersion/go-sasl v0.0.0-20200509203442-7bfe0ed36a21/go.mod h1:iL2twTeMvZnrg54ZoPDNfJaJaqy0xIQFuBdrLsmspwQ=
+github.com/emersion/go-textwrapper v0.0.0-20200911093747-65d896831594 h1:IbFBtwoTQyw0fIM5xv1HF+Y+3ZijDR839WMulgxCcUY=
+github.com/emersion/go-textwrapper v0.0.0-20200911093747-65d896831594/go.mod h1:aqO8z8wPrjkscevZJFVE1wXJrLpC5LtJG7fqLOsPb2U=
+golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/text v0.3.7 h1:olpwvP2KacW1ZWvsR7uQhoyTYvKAupfQrRGBFM352Gk=
 golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
-golang.org/x/text v0.7.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
-golang.org/x/text v0.14.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
-golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
-golang.org/x/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
-golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

imap.go

@@ -1,105 +1,111 @@
-// Package imap implements IMAP4rev2.
-//
-// IMAP4rev2 is defined in RFC 9051.
-//
-// This package contains types and functions common to both the client and
-// server. See the imapclient and imapserver sub-packages.
+// Package imap implements IMAP4rev1 (RFC 3501).
 package imap
 
 import (
-	"fmt"
+	"errors"
 	"io"
+	"strings"
 )
 
-// ConnState describes the connection state.
-//
-// See RFC 9051 section 3.
-type ConnState int
+// A StatusItem is a mailbox status data item that can be retrieved with a
+// STATUS command. See RFC 3501 section 6.3.10.
+type StatusItem string
 
 const (
-	ConnStateNone ConnState = iota
-	ConnStateNotAuthenticated
-	ConnStateAuthenticated
-	ConnStateSelected
-	ConnStateLogout
+	StatusMessages    StatusItem = "MESSAGES"
+	StatusRecent      StatusItem = "RECENT"
+	StatusUidNext     StatusItem = "UIDNEXT"
+	StatusUidValidity StatusItem = "UIDVALIDITY"
+	StatusUnseen      StatusItem = "UNSEEN"
+
+	StatusAppendLimit StatusItem = "APPENDLIMIT"
 )
 
-// String implements fmt.Stringer.
-func (state ConnState) String() string {
-	switch state {
-	case ConnStateNone:
-		return "none"
-	case ConnStateNotAuthenticated:
-		return "not authenticated"
-	case ConnStateAuthenticated:
-		return "authenticated"
-	case ConnStateSelected:
-		return "selected"
-	case ConnStateLogout:
-		return "logout"
+// A FetchItem is a message data item that can be fetched.
+type FetchItem string
+
+// List of items that can be fetched. See RFC 3501 section 6.4.5.
+//
+// Warning: FetchBody will not return the raw message body, instead it will
+// return a subset of FetchBodyStructure.
+const (
+	// Macros
+	FetchAll  FetchItem = "ALL"
+	FetchFast FetchItem = "FAST"
+	FetchFull FetchItem = "FULL"
+
+	// Items
+	FetchBody          FetchItem = "BODY"
+	FetchBodyStructure FetchItem = "BODYSTRUCTURE"
+	FetchEnvelope      FetchItem = "ENVELOPE"
+	FetchFlags         FetchItem = "FLAGS"
+	FetchInternalDate  FetchItem = "INTERNALDATE"
+	FetchRFC822        FetchItem = "RFC822"
+	FetchRFC822Header  FetchItem = "RFC822.HEADER"
+	FetchRFC822Size    FetchItem = "RFC822.SIZE"
+	FetchRFC822Text    FetchItem = "RFC822.TEXT"
+	FetchUid           FetchItem = "UID"
+)
+
+// Expand expands the item if it's a macro.
+func (item FetchItem) Expand() []FetchItem {
+	switch item {
+	case FetchAll:
+		return []FetchItem{FetchFlags, FetchInternalDate, FetchRFC822Size, FetchEnvelope}
+	case FetchFast:
+		return []FetchItem{FetchFlags, FetchInternalDate, FetchRFC822Size}
+	case FetchFull:
+		return []FetchItem{FetchFlags, FetchInternalDate, FetchRFC822Size, FetchEnvelope, FetchBody}
 	default:
-		panic(fmt.Errorf("imap: unknown connection state %v", int(state)))
+		return []FetchItem{item}
 	}
 }
 
-// MailboxAttr is a mailbox attribute.
-//
-// Mailbox attributes are defined in RFC 9051 section 7.3.1.
-type MailboxAttr string
+// FlagsOp is an operation that will be applied on message flags.
+type FlagsOp string
 
 const (
-	// Base attributes
-	MailboxAttrNonExistent   MailboxAttr = "\\NonExistent"
-	MailboxAttrNoInferiors   MailboxAttr = "\\Noinferiors"
-	MailboxAttrNoSelect      MailboxAttr = "\\Noselect"
-	MailboxAttrHasChildren   MailboxAttr = "\\HasChildren"
-	MailboxAttrHasNoChildren MailboxAttr = "\\HasNoChildren"
-	MailboxAttrMarked        MailboxAttr = "\\Marked"
-	MailboxAttrUnmarked      MailboxAttr = "\\Unmarked"
-	MailboxAttrSubscribed    MailboxAttr = "\\Subscribed"
-	MailboxAttrRemote        MailboxAttr = "\\Remote"
-
-	// Role (aka. "special-use") attributes
-	MailboxAttrAll       MailboxAttr = "\\All"
-	MailboxAttrArchive   MailboxAttr = "\\Archive"
-	MailboxAttrDrafts    MailboxAttr = "\\Drafts"
-	MailboxAttrFlagged   MailboxAttr = "\\Flagged"
-	MailboxAttrJunk      MailboxAttr = "\\Junk"
-	MailboxAttrSent      MailboxAttr = "\\Sent"
-	MailboxAttrTrash     MailboxAttr = "\\Trash"
-	MailboxAttrImportant MailboxAttr = "\\Important" // RFC 8457
+	// SetFlags replaces existing flags by new ones.
+	SetFlags FlagsOp = "FLAGS"
+	// AddFlags adds new flags.
+	AddFlags = "+FLAGS"
+	// RemoveFlags removes existing flags.
+	RemoveFlags = "-FLAGS"
 )
 
-// Flag is a message flag.
-//
-// Message flags are defined in RFC 9051 section 2.3.2.
-type Flag string
+// silentOp can be appended to a FlagsOp to prevent the operation from
+// triggering unilateral message updates.
+const silentOp = ".SILENT"
 
-const (
-	// System flags
-	FlagSeen     Flag = "\\Seen"
-	FlagAnswered Flag = "\\Answered"
-	FlagFlagged  Flag = "\\Flagged"
-	FlagDeleted  Flag = "\\Deleted"
-	FlagDraft    Flag = "\\Draft"
+// A StoreItem is a message data item that can be updated.
+type StoreItem string
 
-	// Widely used flags
-	FlagForwarded Flag = "$Forwarded"
-	FlagMDNSent   Flag = "$MDNSent" // Message Disposition Notification sent
-	FlagJunk      Flag = "$Junk"
-	FlagNotJunk   Flag = "$NotJunk"
-	FlagPhishing  Flag = "$Phishing"
-	FlagImportant Flag = "$Important" // RFC 8457
-
-	// Permanent flags
-	FlagWildcard Flag = "\\*"
-)
-
-// LiteralReader is a reader for IMAP literals.
-type LiteralReader interface {
-	io.Reader
-	Size() int64
+// FormatFlagsOp returns the StoreItem that executes the flags operation op.
+func FormatFlagsOp(op FlagsOp, silent bool) StoreItem {
+	s := string(op)
+	if silent {
+		s += silentOp
+	}
+	return StoreItem(s)
 }
 
-// UID is a message unique identifier.
-type UID uint32
+// ParseFlagsOp parses a flags operation from StoreItem.
+func ParseFlagsOp(item StoreItem) (op FlagsOp, silent bool, err error) {
+	itemStr := string(item)
+	silent = strings.HasSuffix(itemStr, silentOp)
+	if silent {
+		itemStr = strings.TrimSuffix(itemStr, silentOp)
+	}
+	op = FlagsOp(itemStr)
+
+	if op != SetFlags && op != AddFlags && op != RemoveFlags {
+		err = errors.New("Unsupported STORE operation")
+	}
+	return
+}
+
+// CharsetReader, if non-nil, defines a function to generate charset-conversion
+// readers, converting from the provided charset into UTF-8. Charsets are always
+// lower-case. utf-8 and us-ascii charsets are handled by default. One of the
+// the CharsetReader's result values must be non-nil.
+var CharsetReader func(charset string, r io.Reader) (io.Reader, error)

internal/acl.go

@@ -1,13 +0,0 @@
-package internal
-
-import (
-	"github.com/emersion/go-imap/v2"
-)
-
-func FormatRights(rm imap.RightModification, rs imap.RightSet) string {
-	s := ""
-	if rm != imap.RightModificationReplace {
-		s = string(rm)
-	}
-	return s + string(rs)
-}

internal/imapnum/numset.go

@@ -1,306 +0,0 @@
-package imapnum
-
-import (
-	"fmt"
-	"strconv"
-	"strings"
-)
-
-// Range represents a single seq-number or seq-range value (RFC 3501 ABNF). Values
-// may be static (e.g. "1", "2:4") or dynamic (e.g. "*", "1:*"). A seq-number is
-// represented by setting Start = Stop. Zero is used to represent "*", which is
-// safe because seq-number uses nz-number rule. The order of values is always
-// Start <= Stop, except when representing "n:*", where Start = n and Stop = 0.
-type Range struct {
-	Start, Stop uint32
-}
-
-// Contains returns true if the seq-number q is contained in range value s.
-// The dynamic value "*" contains only other "*" values, the dynamic range "n:*"
-// contains "*" and all numbers >= n.
-func (s Range) Contains(q uint32) bool {
-	if q == 0 {
-		return s.Stop == 0 // "*" is contained only in "*" and "n:*"
-	}
-	return s.Start != 0 && s.Start <= q && (q <= s.Stop || s.Stop == 0)
-}
-
-// Less returns true if s precedes and does not contain seq-number q.
-func (s Range) Less(q uint32) bool {
-	return (s.Stop < q || q == 0) && s.Stop != 0
-}
-
-// Merge combines range values s and t into a single union if the two
-// intersect or one is a superset of the other. The order of s and t does not
-// matter. If the values cannot be merged, s is returned unmodified and ok is
-// set to false.
-func (s Range) Merge(t Range) (union Range, ok bool) {
-	union = s
-	if s == t {
-		return s, true
-	}
-	if s.Start != 0 && t.Start != 0 {
-		// s and t are any combination of "n", "n:m", or "n:*"
-		if s.Start > t.Start {
-			s, t = t, s
-		}
-		// s starts at or before t, check where it ends
-		if (s.Stop >= t.Stop && t.Stop != 0) || s.Stop == 0 {
-			return s, true // s is a superset of t
-		}
-		// s is "n" or "n:m", if m == ^uint32(0) then t is "n:*"
-		if s.Stop+1 >= t.Start || s.Stop == ^uint32(0) {
-			return Range{s.Start, t.Stop}, true // s intersects or touches t
-		}
-		return union, false
-	}
-	// exactly one of s and t is "*"
-	if s.Start == 0 {
-		if t.Stop == 0 {
-			return t, true // s is "*", t is "n:*"
-		}
-	} else if s.Stop == 0 {
-		return s, true // s is "n:*", t is "*"
-	}
-	return union, false
-}
-
-// String returns range value s as a seq-number or seq-range string.
-func (s Range) String() string {
-	if s.Start == s.Stop {
-		if s.Start == 0 {
-			return "*"
-		}
-		return strconv.FormatUint(uint64(s.Start), 10)
-	}
-	b := strconv.AppendUint(make([]byte, 0, 24), uint64(s.Start), 10)
-	if s.Stop == 0 {
-		return string(append(b, ':', '*'))
-	}
-	return string(strconv.AppendUint(append(b, ':'), uint64(s.Stop), 10))
-}
-
-func (s Range) append(nums []uint32) (out []uint32, ok bool) {
-	if s.Start == 0 || s.Stop == 0 {
-		return nil, false
-	}
-	for n := s.Start; n <= s.Stop; n++ {
-		nums = append(nums, n)
-	}
-	return nums, true
-}
-
-// Set is used to represent a set of message sequence numbers or UIDs (see
-// sequence-set ABNF rule). The zero value is an empty set.
-type Set []Range
-
-// AddNum inserts new numbers into the set. The value 0 represents "*".
-func (s *Set) AddNum(q ...uint32) {
-	for _, v := range q {
-		s.insert(Range{v, v})
-	}
-}
-
-// AddRange inserts a new range into the set.
-func (s *Set) AddRange(start, stop uint32) {
-	if (stop < start && stop != 0) || start == 0 {
-		s.insert(Range{stop, start})
-	} else {
-		s.insert(Range{start, stop})
-	}
-}
-
-// AddSet inserts all values from t into s.
-func (s *Set) AddSet(t Set) {
-	for _, v := range t {
-		s.insert(v)
-	}
-}
-
-// Dynamic returns true if the set contains "*" or "n:*" values.
-func (s Set) Dynamic() bool {
-	return len(s) > 0 && s[len(s)-1].Stop == 0
-}
-
-// Contains returns true if the non-zero sequence number or UID q is contained
-// in the set. The dynamic range "n:*" contains all q >= n. It is the caller's
-// responsibility to handle the special case where q is the maximum UID in the
-// mailbox and q < n (i.e. the set cannot match UIDs against "*:n" or "*" since
-// it doesn't know what the maximum value is).
-func (s Set) Contains(q uint32) bool {
-	if _, ok := s.search(q); ok {
-		return q != 0
-	}
-	return false
-}
-
-// Nums returns a slice of all numbers contained in the set.
-func (s Set) Nums() (nums []uint32, ok bool) {
-	for _, v := range s {
-		nums, ok = v.append(nums)
-		if !ok {
-			return nil, false
-		}
-	}
-	return nums, true
-}
-
-// String returns a sorted representation of all contained number values.
-func (s Set) String() string {
-	if len(s) == 0 {
-		return ""
-	}
-	b := make([]byte, 0, 64)
-	for _, v := range s {
-		b = append(b, ',')
-		if v.Start == 0 {
-			b = append(b, '*')
-			continue
-		}
-		b = strconv.AppendUint(b, uint64(v.Start), 10)
-		if v.Start != v.Stop {
-			if v.Stop == 0 {
-				b = append(b, ':', '*')
-				continue
-			}
-			b = strconv.AppendUint(append(b, ':'), uint64(v.Stop), 10)
-		}
-	}
-	return string(b[1:])
-}
-
-// insert adds range value v to the set.
-func (ptr *Set) insert(v Range) {
-	s := *ptr
-	defer func() {
-		*ptr = s
-	}()
-
-	i, _ := s.search(v.Start)
-	merged := false
-	if i > 0 {
-		// try merging with the preceding entry (e.g. "1,4".insert(2), i == 1)
-		s[i-1], merged = s[i-1].Merge(v)
-	}
-	if i == len(s) {
-		// v was either merged with the last entry or needs to be appended
-		if !merged {
-			s.insertAt(i, v)
-		}
-		return
-	} else if merged {
-		i--
-	} else if s[i], merged = s[i].Merge(v); !merged {
-		s.insertAt(i, v) // insert in the middle (e.g. "1,5".insert(3), i == 1)
-		return
-	}
-	// v was merged with s[i], continue trying to merge until the end
-	for j := i + 1; j < len(s); j++ {
-		if s[i], merged = s[i].Merge(s[j]); !merged {
-			if j > i+1 {
-				// cut out all entries between i and j that were merged
-				s = append(s[:i+1], s[j:]...)
-			}
-			return
-		}
-	}
-	// everything after s[i] was merged
-	s = s[:i+1]
-}
-
-// insertAt inserts a new range value v at index i, resizing s.Set as needed.
-func (ptr *Set) insertAt(i int, v Range) {
-	s := *ptr
-	defer func() {
-		*ptr = s
-	}()
-
-	if n := len(s); i == n {
-		// insert at the end
-		s = append(s, v)
-		return
-	} else if n < cap(s) {
-		// enough space, shift everything at and after i to the right
-		s = s[:n+1]
-		copy(s[i+1:], s[i:])
-	} else {
-		// allocate new slice and copy everything, n is at least 1
-		set := make([]Range, n+1, n*2)
-		copy(set, s[:i])
-		copy(set[i+1:], s[i:])
-		s = set
-	}
-	s[i] = v
-}
-
-// search attempts to find the index of the range set value that contains q.
-// If no values contain q, the returned index is the position where q should be
-// inserted and ok is set to false.
-func (s Set) search(q uint32) (i int, ok bool) {
-	min, max := 0, len(s)-1
-	for min < max {
-		if mid := (min + max) >> 1; s[mid].Less(q) {
-			min = mid + 1
-		} else {
-			max = mid
-		}
-	}
-	if max < 0 || s[min].Less(q) {
-		return len(s), false // q is the new largest value
-	}
-	return min, s[min].Contains(q)
-}
-
-// errBadNumSet is used to report problems with the format of a number set
-// value.
-type errBadNumSet string
-
-func (err errBadNumSet) Error() string {
-	return fmt.Sprintf("imap: bad number set value %q", string(err))
-}
-
-// parseNum parses a single seq-number value (non-zero uint32 or "*").
-func parseNum(v string) (uint32, error) {
-	if n, err := strconv.ParseUint(v, 10, 32); err == nil && v[0] != '0' {
-		return uint32(n), nil
-	} else if v == "*" {
-		return 0, nil
-	}
-	return 0, errBadNumSet(v)
-}
-
-// parseNumRange creates a new seq instance by parsing strings in the format
-// "n" or "n:m", where n and/or m may be "*". An error is returned for invalid
-// values.
-func parseNumRange(v string) (Range, error) {
-	var (
-		r   Range
-		err error
-	)
-	if sep := strings.IndexRune(v, ':'); sep < 0 {
-		r.Start, err = parseNum(v)
-		r.Stop = r.Start
-		return r, err
-	} else if r.Start, err = parseNum(v[:sep]); err == nil {
-		if r.Stop, err = parseNum(v[sep+1:]); err == nil {
-			if (r.Stop < r.Start && r.Stop != 0) || r.Start == 0 {
-				r.Start, r.Stop = r.Stop, r.Start
-			}
-			return r, nil
-		}
-	}
-	return r, errBadNumSet(v)
-}
-
-// ParseSet returns a new Set after parsing the set string.
-func ParseSet(set string) (Set, error) {
-	var s Set
-	for _, sv := range strings.Split(set, ",") {
-		r, err := parseNumRange(sv)
-		if err != nil {
-			return s, err
-		}
-		s.AddRange(r.Start, r.Stop)
-	}
-	return s, nil
-}

internal/imapwire/decoder.go

@@ -1,654 +0,0 @@
-package imapwire
-
-import (
-	"bufio"
-	"fmt"
-	"io"
-	"strconv"
-	"strings"
-	"unicode"
-
-	"github.com/emersion/go-imap/v2"
-	"github.com/emersion/go-imap/v2/internal/imapnum"
-	"github.com/emersion/go-imap/v2/internal/utf7"
-)
-
-// This limits the max list nesting depth to prevent stack overflow.
-const maxListDepth = 1000
-
-// IsAtomChar returns true if ch is an ATOM-CHAR.
-func IsAtomChar(ch byte) bool {
-	switch ch {
-	case '(', ')', '{', ' ', '%', '*', '"', '\\', ']':
-		return false
-	default:
-		return !unicode.IsControl(rune(ch))
-	}
-}
-
-// Is non-empty char
-func isAStringChar(ch byte) bool {
-	return IsAtomChar(ch) || ch == ']'
-}
-
-// DecoderExpectError is an error due to the Decoder.Expect family of methods.
-type DecoderExpectError struct {
-	Message string
-}
-
-func (err *DecoderExpectError) Error() string {
-	return fmt.Sprintf("imapwire: %v", err.Message)
-}
-
-// A Decoder reads IMAP data.
-//
-// There are multiple families of methods:
-//
-//   - Methods directly named after IMAP grammar elements attempt to decode
-//     said element, and return false if it's another element.
-//   - "Expect" methods do the same, but set the decoder error (see Err) on
-//     failure.
-type Decoder struct {
-	// CheckBufferedLiteralFunc is called when a literal is about to be decoded
-	// and needs to be fully buffered in memory.
-	CheckBufferedLiteralFunc func(size int64, nonSync bool) error
-	// MaxSize defines a maximum number of bytes to be read from the input.
-	// Literals are ignored.
-	MaxSize int64
-
-	r         *bufio.Reader
-	side      ConnSide
-	err       error
-	literal   bool
-	crlf      bool
-	listDepth int
-	readBytes int64
-}
-
-// NewDecoder creates a new decoder.
-func NewDecoder(r *bufio.Reader, side ConnSide) *Decoder {
-	return &Decoder{r: r, side: side}
-}
-
-func (dec *Decoder) mustUnreadByte() {
-	if err := dec.r.UnreadByte(); err != nil {
-		panic(fmt.Errorf("imapwire: failed to unread byte: %v", err))
-	}
-	dec.readBytes--
-}
-
-// Err returns the decoder error, if any.
-func (dec *Decoder) Err() error {
-	return dec.err
-}
-
-func (dec *Decoder) returnErr(err error) bool {
-	if err == nil {
-		return true
-	}
-	if dec.err == nil {
-		dec.err = err
-	}
-	return false
-}
-
-func (dec *Decoder) readByte() (byte, bool) {
-	if dec.MaxSize > 0 && dec.readBytes > dec.MaxSize {
-		return 0, dec.returnErr(fmt.Errorf("imapwire: max size exceeded"))
-	}
-	dec.crlf = false
-	if dec.literal {
-		return 0, dec.returnErr(fmt.Errorf("imapwire: cannot decode while a literal is open"))
-	}
-	b, err := dec.r.ReadByte()
-	if err != nil {
-		if err == io.EOF {
-			err = io.ErrUnexpectedEOF
-		}
-		return b, dec.returnErr(err)
-	}
-	dec.readBytes++
-	return b, true
-}
-
-func (dec *Decoder) acceptByte(want byte) bool {
-	got, ok := dec.readByte()
-	if !ok {
-		return false
-	} else if got != want {
-		dec.mustUnreadByte()
-		return false
-	}
-	return true
-}
-
-// EOF returns true if end-of-file is reached.
-func (dec *Decoder) EOF() bool {
-	_, err := dec.r.ReadByte()
-	if err == io.EOF {
-		return true
-	} else if err != nil {
-		return dec.returnErr(err)
-	}
-	dec.mustUnreadByte()
-	return false
-}
-
-// Expect sets the decoder error if ok is false.
-func (dec *Decoder) Expect(ok bool, name string) bool {
-	if !ok {
-		msg := fmt.Sprintf("expected %v", name)
-		if dec.r.Buffered() > 0 {
-			b, _ := dec.r.Peek(1)
-			msg += fmt.Sprintf(", got %q", b)
-		}
-		return dec.returnErr(&DecoderExpectError{Message: msg})
-	}
-	return true
-}
-
-func (dec *Decoder) SP() bool {
-	if dec.acceptByte(' ') {
-		// https://github.com/emersion/go-imap/issues/571
-		b, ok := dec.readByte()
-		if !ok {
-			return false
-		}
-		dec.mustUnreadByte()
-		return b != '\r' && b != '\n'
-	}
-
-	// Special case: SP is optional if the next field is a parenthesized list
-	b, ok := dec.readByte()
-	if !ok {
-		return false
-	}
-	dec.mustUnreadByte()
-	return b == '('
-}
-
-func (dec *Decoder) ExpectSP() bool {
-	return dec.Expect(dec.SP(), "SP")
-}
-
-func (dec *Decoder) CRLF() bool {
-	dec.acceptByte(' ')  // https://github.com/emersion/go-imap/issues/540
-	dec.acceptByte('\r') // be liberal in what we receive and accept lone LF
-	if !dec.acceptByte('\n') {
-		return false
-	}
-	dec.crlf = true
-	return true
-}
-
-func (dec *Decoder) ExpectCRLF() bool {
-	return dec.Expect(dec.CRLF(), "CRLF")
-}
-
-func (dec *Decoder) Func(ptr *string, valid func(ch byte) bool) bool {
-	var sb strings.Builder
-	for {
-		b, ok := dec.readByte()
-		if !ok {
-			return false
-		}
-
-		if !valid(b) {
-			dec.mustUnreadByte()
-			break
-		}
-
-		sb.WriteByte(b)
-	}
-	if sb.Len() == 0 {
-		return false
-	}
-	*ptr = sb.String()
-	return true
-}
-
-func (dec *Decoder) Atom(ptr *string) bool {
-	return dec.Func(ptr, IsAtomChar)
-}
-
-func (dec *Decoder) ExpectAtom(ptr *string) bool {
-	return dec.Expect(dec.Atom(ptr), "atom")
-}
-
-func (dec *Decoder) ExpectNIL() bool {
-	var s string
-	return dec.ExpectAtom(&s) && dec.Expect(s == "NIL", "NIL")
-}
-
-func (dec *Decoder) Special(b byte) bool {
-	return dec.acceptByte(b)
-}
-
-func (dec *Decoder) ExpectSpecial(b byte) bool {
-	return dec.Expect(dec.Special(b), fmt.Sprintf("'%v'", string(b)))
-}
-
-func (dec *Decoder) Text(ptr *string) bool {
-	var sb strings.Builder
-	for {
-		b, ok := dec.readByte()
-		if !ok {
-			return false
-		} else if b == '\r' || b == '\n' {
-			dec.mustUnreadByte()
-			break
-		}
-		sb.WriteByte(b)
-	}
-	if sb.Len() == 0 {
-		return false
-	}
-	*ptr = sb.String()
-	return true
-}
-
-func (dec *Decoder) ExpectText(ptr *string) bool {
-	return dec.Expect(dec.Text(ptr), "text")
-}
-
-func (dec *Decoder) DiscardUntilByte(untilCh byte) {
-	for {
-		ch, ok := dec.readByte()
-		if !ok {
-			return
-		} else if ch == untilCh {
-			dec.mustUnreadByte()
-			return
-		}
-	}
-}
-
-func (dec *Decoder) DiscardLine() {
-	if dec.crlf {
-		return
-	}
-	var text string
-	dec.Text(&text)
-	dec.CRLF()
-}
-
-func (dec *Decoder) DiscardValue() bool {
-	var s string
-	if dec.String(&s) {
-		return true
-	}
-
-	isList, err := dec.List(func() error {
-		if !dec.DiscardValue() {
-			return dec.Err()
-		}
-		return nil
-	})
-	if err != nil {
-		return false
-	} else if isList {
-		return true
-	}
-
-	if dec.Atom(&s) {
-		return true
-	}
-
-	dec.Expect(false, "value")
-	return false
-}
-
-func (dec *Decoder) numberStr() (s string, ok bool) {
-	var sb strings.Builder
-	for {
-		ch, ok := dec.readByte()
-		if !ok {
-			return "", false
-		} else if ch < '0' || ch > '9' {
-			dec.mustUnreadByte()
-			break
-		}
-		sb.WriteByte(ch)
-	}
-	if sb.Len() == 0 {
-		return "", false
-	}
-	return sb.String(), true
-}
-
-func (dec *Decoder) Number(ptr *uint32) bool {
-	s, ok := dec.numberStr()
-	if !ok {
-		return false
-	}
-	v64, err := strconv.ParseUint(s, 10, 32)
-	if err != nil {
-		return false // can happen on overflow
-	}
-	*ptr = uint32(v64)
-	return true
-}
-
-func (dec *Decoder) ExpectNumber(ptr *uint32) bool {
-	return dec.Expect(dec.Number(ptr), "number")
-}
-
-func (dec *Decoder) ExpectBodyFldOctets(ptr *uint32) bool {
-	// Workaround: some servers incorrectly return "-1" for the body structure
-	// size. See:
-	// https://github.com/emersion/go-imap/issues/534
-	if dec.acceptByte('-') {
-		*ptr = 0
-		return dec.Expect(dec.acceptByte('1'), "-1 (body-fld-octets workaround)")
-	}
-	return dec.ExpectNumber(ptr)
-}
-
-func (dec *Decoder) Number64(ptr *int64) bool {
-	s, ok := dec.numberStr()
-	if !ok {
-		return false
-	}
-	v, err := strconv.ParseInt(s, 10, 64)
-	if err != nil {
-		return false // can happen on overflow
-	}
-	*ptr = v
-	return true
-}
-
-func (dec *Decoder) ExpectNumber64(ptr *int64) bool {
-	return dec.Expect(dec.Number64(ptr), "number64")
-}
-
-func (dec *Decoder) ModSeq(ptr *uint64) bool {
-	s, ok := dec.numberStr()
-	if !ok {
-		return false
-	}
-	v, err := strconv.ParseUint(s, 10, 64)
-	if err != nil {
-		return false // can happen on overflow
-	}
-	*ptr = v
-	return true
-}
-
-func (dec *Decoder) ExpectModSeq(ptr *uint64) bool {
-	return dec.Expect(dec.ModSeq(ptr), "mod-sequence-value")
-}
-
-func (dec *Decoder) Quoted(ptr *string) bool {
-	if !dec.Special('"') {
-		return false
-	}
-	var sb strings.Builder
-	for {
-		ch, ok := dec.readByte()
-		if !ok {
-			return false
-		}
-
-		if ch == '"' {
-			break
-		}
-
-		if ch == '\\' {
-			ch, ok = dec.readByte()
-			if !ok {
-				return false
-			}
-		}
-
-		sb.WriteByte(ch)
-	}
-	*ptr = sb.String()
-	return true
-}
-
-func (dec *Decoder) ExpectAString(ptr *string) bool {
-	if dec.Quoted(ptr) {
-		return true
-	}
-	if dec.Literal(ptr) {
-		return true
-	}
-	// We cannot do dec.Atom(ptr) here because sometimes mailbox names are unquoted,
-	// and they can contain special characters like `]`.
-	return dec.Expect(dec.Func(ptr, isAStringChar), "ASTRING-CHAR")
-}
-
-func (dec *Decoder) String(ptr *string) bool {
-	return dec.Quoted(ptr) || dec.Literal(ptr)
-}
-
-func (dec *Decoder) ExpectString(ptr *string) bool {
-	return dec.Expect(dec.String(ptr), "string")
-}
-
-func (dec *Decoder) ExpectNString(ptr *string) bool {
-	var s string
-	if dec.Atom(&s) {
-		if !dec.Expect(s == "NIL", "nstring") {
-			return false
-		}
-		*ptr = ""
-		return true
-	}
-	return dec.ExpectString(ptr)
-}
-
-func (dec *Decoder) ExpectNStringReader() (lit *LiteralReader, nonSync, ok bool) {
-	var s string
-	if dec.Atom(&s) {
-		if !dec.Expect(s == "NIL", "nstring") {
-			return nil, false, false
-		}
-		return nil, true, true
-	}
-	// TODO: read quoted string as a string instead of buffering
-	if dec.Quoted(&s) {
-		return newLiteralReaderFromString(s), true, true
-	}
-	if lit, nonSync, ok = dec.LiteralReader(); ok {
-		return lit, nonSync, true
-	} else {
-		return nil, false, dec.Expect(false, "nstring")
-	}
-}
-
-func (dec *Decoder) List(f func() error) (isList bool, err error) {
-	if !dec.Special('(') {
-		return false, nil
-	}
-	if dec.Special(')') {
-		return true, nil
-	}
-
-	dec.listDepth++
-	defer func() {
-		dec.listDepth--
-	}()
-
-	if dec.listDepth >= maxListDepth {
-		return false, fmt.Errorf("imapwire: exceeded max depth")
-	}
-
-	for {
-		if err := f(); err != nil {
-			return true, err
-		}
-
-		if dec.Special(')') {
-			return true, nil
-		} else if !dec.ExpectSP() {
-			return true, dec.Err()
-		}
-	}
-}
-
-func (dec *Decoder) ExpectList(f func() error) error {
-	isList, err := dec.List(f)
-	if err != nil {
-		return err
-	} else if !dec.Expect(isList, "(") {
-		return dec.Err()
-	}
-	return nil
-}
-
-func (dec *Decoder) ExpectNList(f func() error) error {
-	var s string
-	if dec.Atom(&s) {
-		if !dec.Expect(s == "NIL", "NIL") {
-			return dec.Err()
-		}
-		return nil
-	}
-	return dec.ExpectList(f)
-}
-
-func (dec *Decoder) ExpectMailbox(ptr *string) bool {
-	var name string
-	if !dec.ExpectAString(&name) {
-		return false
-	}
-	if strings.EqualFold(name, "INBOX") {
-		*ptr = "INBOX"
-		return true
-	}
-	name, err := utf7.Decode(name)
-	if err == nil {
-		*ptr = name
-	}
-	return dec.returnErr(err)
-}
-
-func (dec *Decoder) ExpectUID(ptr *imap.UID) bool {
-	var num uint32
-	if !dec.ExpectNumber(&num) {
-		return false
-	}
-	*ptr = imap.UID(num)
-	return true
-}
-
-func (dec *Decoder) ExpectNumSet(kind NumKind, ptr *imap.NumSet) bool {
-	if dec.Special('$') {
-		*ptr = imap.SearchRes()
-		return true
-	}
-
-	var s string
-	if !dec.Expect(dec.Func(&s, isNumSetChar), "sequence-set") {
-		return false
-	}
-	numSet, err := imapnum.ParseSet(s)
-	if err != nil {
-		return dec.returnErr(err)
-	}
-
-	switch kind {
-	case NumKindSeq:
-		*ptr = seqSetFromNumSet(numSet)
-	case NumKindUID:
-		*ptr = uidSetFromNumSet(numSet)
-	}
-	return true
-}
-
-func (dec *Decoder) ExpectUIDSet(ptr *imap.UIDSet) bool {
-	var numSet imap.NumSet
-	ok := dec.ExpectNumSet(NumKindUID, &numSet)
-	if ok {
-		*ptr = numSet.(imap.UIDSet)
-	}
-	return ok
-}
-
-func isNumSetChar(ch byte) bool {
-	return ch == '*' || IsAtomChar(ch)
-}
-
-func (dec *Decoder) Literal(ptr *string) bool {
-	lit, nonSync, ok := dec.LiteralReader()
-	if !ok {
-		return false
-	}
-	if dec.CheckBufferedLiteralFunc != nil {
-		if err := dec.CheckBufferedLiteralFunc(lit.Size(), nonSync); err != nil {
-			lit.cancel()
-			return false
-		}
-	}
-	var sb strings.Builder
-	_, err := io.Copy(&sb, lit)
-	if err == nil {
-		*ptr = sb.String()
-	}
-	return dec.returnErr(err)
-}
-
-func (dec *Decoder) LiteralReader() (lit *LiteralReader, nonSync, ok bool) {
-	if !dec.Special('{') {
-		return nil, false, false
-	}
-	var size int64
-	if !dec.ExpectNumber64(&size) {
-		return nil, false, false
-	}
-	if dec.side == ConnSideServer {
-		nonSync = dec.acceptByte('+')
-	}
-	if !dec.ExpectSpecial('}') || !dec.ExpectCRLF() {
-		return nil, false, false
-	}
-	dec.literal = true
-	lit = &LiteralReader{
-		dec:  dec,
-		size: size,
-		r:    io.LimitReader(dec.r, size),
-	}
-	return lit, nonSync, true
-}
-
-func (dec *Decoder) ExpectLiteralReader() (lit *LiteralReader, nonSync bool, err error) {
-	lit, nonSync, ok := dec.LiteralReader()
-	if !dec.Expect(ok, "literal") {
-		return nil, false, dec.Err()
-	}
-	return lit, nonSync, nil
-}
-
-type LiteralReader struct {
-	dec  *Decoder
-	size int64
-	r    io.Reader
-}
-
-func newLiteralReaderFromString(s string) *LiteralReader {
-	return &LiteralReader{
-		size: int64(len(s)),
-		r:    strings.NewReader(s),
-	}
-}
-
-func (lit *LiteralReader) Size() int64 {
-	return lit.size
-}
-
-func (lit *LiteralReader) Read(b []byte) (int, error) {
-	n, err := lit.r.Read(b)
-	if err == io.EOF {
-		lit.cancel()
-	}
-	return n, err
-}
-
-func (lit *LiteralReader) cancel() {
-	if lit.dec == nil {
-		return
-	}
-	lit.dec.literal = false
-	lit.dec = nil
-}

internal/imapwire/encoder.go

@@ -1,341 +0,0 @@
-package imapwire
-
-import (
-	"bufio"
-	"fmt"
-	"io"
-	"strconv"
-	"strings"
-	"unicode"
-
-	"github.com/emersion/go-imap/v2"
-	"github.com/emersion/go-imap/v2/internal/utf7"
-)
-
-// An Encoder writes IMAP data.
-//
-// Most methods don't return an error, instead they defer error handling until
-// CRLF is called. These methods return the Encoder so that calls can be
-// chained.
-type Encoder struct {
-	// QuotedUTF8 allows raw UTF-8 in quoted strings. This requires IMAP4rev2
-	// to be available, or UTF8=ACCEPT to be enabled.
-	QuotedUTF8 bool
-	// LiteralMinus enables non-synchronizing literals for short payloads.
-	// This requires IMAP4rev2 or LITERAL-. This is only meaningful for
-	// clients.
-	LiteralMinus bool
-	// LiteralPlus enables non-synchronizing literals for all payloads. This
-	// requires LITERAL+. This is only meaningful for clients.
-	LiteralPlus bool
-	// NewContinuationRequest creates a new continuation request. This is only
-	// meaningful for clients.
-	NewContinuationRequest func() *ContinuationRequest
-
-	w       *bufio.Writer
-	side    ConnSide
-	err     error
-	literal bool
-}
-
-// NewEncoder creates a new encoder.
-func NewEncoder(w *bufio.Writer, side ConnSide) *Encoder {
-	return &Encoder{w: w, side: side}
-}
-
-func (enc *Encoder) setErr(err error) {
-	if enc.err == nil {
-		enc.err = err
-	}
-}
-
-func (enc *Encoder) writeString(s string) *Encoder {
-	if enc.err != nil {
-		return enc
-	}
-	if enc.literal {
-		enc.err = fmt.Errorf("imapwire: cannot encode while a literal is open")
-		return enc
-	}
-	if _, err := enc.w.WriteString(s); err != nil {
-		enc.err = err
-	}
-	return enc
-}
-
-// CRLF writes a "\r\n" sequence and flushes the buffered writer.
-func (enc *Encoder) CRLF() error {
-	enc.writeString("\r\n")
-	if enc.err != nil {
-		return enc.err
-	}
-	return enc.w.Flush()
-}
-
-func (enc *Encoder) Atom(s string) *Encoder {
-	return enc.writeString(s)
-}
-
-func (enc *Encoder) SP() *Encoder {
-	return enc.writeString(" ")
-}
-
-func (enc *Encoder) Special(ch byte) *Encoder {
-	return enc.writeString(string(ch))
-}
-
-func (enc *Encoder) Quoted(s string) *Encoder {
-	var sb strings.Builder
-	sb.Grow(2 + len(s))
-	sb.WriteByte('"')
-	for i := 0; i < len(s); i++ {
-		ch := s[i]
-		if ch == '"' || ch == '\\' {
-			sb.WriteByte('\\')
-		}
-		sb.WriteByte(ch)
-	}
-	sb.WriteByte('"')
-	return enc.writeString(sb.String())
-}
-
-func (enc *Encoder) String(s string) *Encoder {
-	if !enc.validQuoted(s) {
-		enc.stringLiteral(s)
-		return enc
-	}
-	return enc.Quoted(s)
-}
-
-func (enc *Encoder) validQuoted(s string) bool {
-	if len(s) > 4096 {
-		return false
-	}
-
-	for i := 0; i < len(s); i++ {
-		ch := s[i]
-
-		// NUL, CR and LF are never valid
-		switch ch {
-		case 0, '\r', '\n':
-			return false
-		}
-
-		if !enc.QuotedUTF8 && ch > unicode.MaxASCII {
-			return false
-		}
-	}
-	return true
-}
-
-func (enc *Encoder) stringLiteral(s string) {
-	var sync *ContinuationRequest
-	if enc.side == ConnSideClient && (!enc.LiteralMinus || len(s) > 4096) && !enc.LiteralPlus {
-		if enc.NewContinuationRequest != nil {
-			sync = enc.NewContinuationRequest()
-		}
-		if sync == nil {
-			enc.setErr(fmt.Errorf("imapwire: cannot send synchronizing literal"))
-			return
-		}
-	}
-	wc := enc.Literal(int64(len(s)), sync)
-	_, writeErr := io.WriteString(wc, s)
-	closeErr := wc.Close()
-	if writeErr != nil {
-		enc.setErr(writeErr)
-	} else if closeErr != nil {
-		enc.setErr(closeErr)
-	}
-}
-
-func (enc *Encoder) Mailbox(name string) *Encoder {
-	if strings.EqualFold(name, "INBOX") {
-		return enc.Atom("INBOX")
-	} else {
-		if enc.QuotedUTF8 {
-			name = utf7.Escape(name)
-		} else {
-			name = utf7.Encode(name)
-		}
-		return enc.String(name)
-	}
-}
-
-func (enc *Encoder) NumSet(numSet imap.NumSet) *Encoder {
-	s := numSet.String()
-	if s == "" {
-		enc.setErr(fmt.Errorf("imapwire: cannot encode empty sequence set"))
-		return enc
-	}
-	return enc.writeString(s)
-}
-
-func (enc *Encoder) Flag(flag imap.Flag) *Encoder {
-	if flag != "\\*" && !isValidFlag(string(flag)) {
-		enc.setErr(fmt.Errorf("imapwire: invalid flag %q", flag))
-		return enc
-	}
-	return enc.writeString(string(flag))
-}
-
-func (enc *Encoder) MailboxAttr(attr imap.MailboxAttr) *Encoder {
-	if !strings.HasPrefix(string(attr), "\\") || !isValidFlag(string(attr)) {
-		enc.setErr(fmt.Errorf("imapwire: invalid mailbox attribute %q", attr))
-		return enc
-	}
-	return enc.writeString(string(attr))
-}
-
-// isValidFlag checks whether the provided string satisfies
-// flag-keyword / flag-extension.
-func isValidFlag(s string) bool {
-	for i := 0; i < len(s); i++ {
-		ch := s[i]
-		if ch == '\\' {
-			if i != 0 {
-				return false
-			}
-		} else {
-			if !IsAtomChar(ch) {
-				return false
-			}
-		}
-	}
-	return len(s) > 0
-}
-
-func (enc *Encoder) Number(v uint32) *Encoder {
-	return enc.writeString(strconv.FormatUint(uint64(v), 10))
-}
-
-func (enc *Encoder) Number64(v int64) *Encoder {
-	// TODO: disallow negative values
-	return enc.writeString(strconv.FormatInt(v, 10))
-}
-
-func (enc *Encoder) ModSeq(v uint64) *Encoder {
-	// TODO: disallow zero values
-	return enc.writeString(strconv.FormatUint(v, 10))
-}
-
-// List writes a parenthesized list.
-func (enc *Encoder) List(n int, f func(i int)) *Encoder {
-	enc.Special('(')
-	for i := 0; i < n; i++ {
-		if i > 0 {
-			enc.SP()
-		}
-		f(i)
-	}
-	enc.Special(')')
-	return enc
-}
-
-func (enc *Encoder) BeginList() *ListEncoder {
-	enc.Special('(')
-	return &ListEncoder{enc: enc}
-}
-
-func (enc *Encoder) NIL() *Encoder {
-	return enc.Atom("NIL")
-}
-
-func (enc *Encoder) Text(s string) *Encoder {
-	return enc.writeString(s)
-}
-
-func (enc *Encoder) UID(uid imap.UID) *Encoder {
-	return enc.Number(uint32(uid))
-}
-
-// Literal writes a literal.
-//
-// The caller must write exactly size bytes to the returned writer.
-//
-// If sync is non-nil, the literal is synchronizing: the encoder will wait for
-// nil to be sent to the channel before writing the literal data. If an error
-// is sent to the channel, the literal will be cancelled.
-func (enc *Encoder) Literal(size int64, sync *ContinuationRequest) io.WriteCloser {
-	if sync != nil && enc.side == ConnSideServer {
-		panic("imapwire: sync must be nil on a server-side Encoder.Literal")
-	}
-
-	// TODO: literal8
-	enc.writeString("{")
-	enc.Number64(size)
-	if sync == nil && enc.side == ConnSideClient {
-		enc.writeString("+")
-	}
-	enc.writeString("}")
-
-	if sync == nil {
-		enc.writeString("\r\n")
-	} else {
-		if err := enc.CRLF(); err != nil {
-			return errorWriter{err}
-		}
-		if _, err := sync.Wait(); err != nil {
-			enc.setErr(err)
-			return errorWriter{err}
-		}
-	}
-
-	enc.literal = true
-	return &literalWriter{
-		enc: enc,
-		n:   size,
-	}
-}
-
-type errorWriter struct {
-	err error
-}
-
-func (ew errorWriter) Write(b []byte) (int, error) {
-	return 0, ew.err
-}
-
-func (ew errorWriter) Close() error {
-	return ew.err
-}
-
-type literalWriter struct {
-	enc *Encoder
-	n   int64
-}
-
-func (lw *literalWriter) Write(b []byte) (int, error) {
-	if lw.n-int64(len(b)) < 0 {
-		return 0, fmt.Errorf("wrote too many bytes in literal")
-	}
-	n, err := lw.enc.w.Write(b)
-	lw.n -= int64(n)
-	return n, err
-}
-
-func (lw *literalWriter) Close() error {
-	lw.enc.literal = false
-	if lw.n != 0 {
-		return fmt.Errorf("wrote too few bytes in literal (%v remaining)", lw.n)
-	}
-	return nil
-}
-
-type ListEncoder struct {
-	enc *Encoder
-	n   int
-}
-
-func (le *ListEncoder) Item() *Encoder {
-	if le.n > 0 {
-		le.enc.SP()
-	}
-	le.n++
-	return le.enc
-}
-
-func (le *ListEncoder) End() {
-	le.enc.Special(')')
-	le.enc = nil
-}

internal/imapwire/imapwire.go

@@ -1,47 +0,0 @@
-// Package imapwire implements the IMAP wire protocol.
-//
-// The IMAP wire protocol is defined in RFC 9051 section 4.
-package imapwire
-
-import (
-	"fmt"
-)
-
-// ConnSide describes the side of a connection: client or server.
-type ConnSide int
-
-const (
-	ConnSideClient ConnSide = 1 + iota
-	ConnSideServer
-)
-
-// ContinuationRequest is a continuation request.
-//
-// The sender must call either Done or Cancel. The receiver must call Wait.
-type ContinuationRequest struct {
-	done chan struct{}
-	err  error
-	text string
-}
-
-func NewContinuationRequest() *ContinuationRequest {
-	return &ContinuationRequest{done: make(chan struct{})}
-}
-
-func (cont *ContinuationRequest) Cancel(err error) {
-	if err == nil {
-		err = fmt.Errorf("imapwire: continuation request cancelled")
-	}
-	cont.err = err
-	close(cont.done)
-}
-
-func (cont *ContinuationRequest) Done(text string) {
-	cont.text = text
-	close(cont.done)
-}
-
-func (cont *ContinuationRequest) Wait() (string, error) {
-	<-cont.done
-	return cont.text, cont.err
-}

internal/imapwire/num.go

@@ -1,39 +0,0 @@
-package imapwire
-
-import (
-	"unsafe"
-
-	"github.com/emersion/go-imap/v2"
-	"github.com/emersion/go-imap/v2/internal/imapnum"
-)
-
-type NumKind int
-
-const (
-	NumKindSeq NumKind = iota + 1
-	NumKindUID
-)
-
-func seqSetFromNumSet(s imapnum.Set) imap.SeqSet {
-	return *(*imap.SeqSet)(unsafe.Pointer(&s))
-}
-
-func uidSetFromNumSet(s imapnum.Set) imap.UIDSet {
-	return *(*imap.UIDSet)(unsafe.Pointer(&s))
-}
-
-func NumSetKind(numSet imap.NumSet) NumKind {
-	switch numSet.(type) {
-	case imap.SeqSet:
-		return NumKindSeq
-	case imap.UIDSet:
-		return NumKindUID
-	default:
-		panic("imap: invalid NumSet type")
-	}
-}
-
-func ParseSeqSet(s string) (imap.SeqSet, error) {
-	numSet, err := imapnum.ParseSet(s)
-	return seqSetFromNumSet(numSet), err
-}

internal/internal.go

@@ -1,170 +0,0 @@
-package internal
-
-import (
-	"fmt"
-	"strings"
-	"sync"
-	"time"
-
-	"github.com/emersion/go-imap/v2"
-	"github.com/emersion/go-imap/v2/internal/imapwire"
-)
-
-const (
-	DateTimeLayout = "_2-Jan-2006 15:04:05 -0700"
-	DateLayout     = "2-Jan-2006"
-)
-
-const FlagRecent imap.Flag = "\\Recent" // removed in IMAP4rev2
-
-func DecodeDateTime(dec *imapwire.Decoder) (time.Time, error) {
-	var s string
-	if !dec.Quoted(&s) {
-		return time.Time{}, nil
-	}
-	t, err := time.Parse(DateTimeLayout, s)
-	if err != nil {
-		return time.Time{}, fmt.Errorf("in date-time: %v", err) // TODO: use imapwire.DecodeExpectError?
-	}
-	return t, err
-}
-
-func ExpectDateTime(dec *imapwire.Decoder) (time.Time, error) {
-	t, err := DecodeDateTime(dec)
-	if err != nil {
-		return t, err
-	}
-	if !dec.Expect(!t.IsZero(), "date-time") {
-		return t, dec.Err()
-	}
-	return t, nil
-}
-
-func ExpectDate(dec *imapwire.Decoder) (time.Time, error) {
-	var s string
-	if !dec.ExpectAString(&s) {
-		return time.Time{}, dec.Err()
-	}
-	t, err := time.Parse(DateLayout, s)
-	if err != nil {
-		return time.Time{}, fmt.Errorf("in date: %v", err) // use imapwire.DecodeExpectError?
-	}
-	return t, nil
-}
-
-func ExpectFlagList(dec *imapwire.Decoder) ([]imap.Flag, error) {
-	var flags []imap.Flag
-	err := dec.ExpectList(func() error {
-		// Some servers start the list with a space, so we need to skip it
-		// https://github.com/emersion/go-imap/pull/633
-		dec.SP()
-
-		flag, err := ExpectFlag(dec)
-		if err != nil {
-			return err
-		}
-		flags = append(flags, flag)
-		return nil
-	})
-	return flags, err
-}
-
-func ExpectFlag(dec *imapwire.Decoder) (imap.Flag, error) {
-	isSystem := dec.Special('\\')
-	if isSystem && dec.Special('*') {
-		return imap.FlagWildcard, nil // flag-perm
-	}
-	var name string
-	if !dec.ExpectAtom(&name) {
-		return "", fmt.Errorf("in flag: %w", dec.Err())
-	}
-	if isSystem {
-		name = "\\" + name
-	}
-	return canonicalFlag(name), nil
-}
-
-func ExpectMailboxAttrList(dec *imapwire.Decoder) ([]imap.MailboxAttr, error) {
-	var attrs []imap.MailboxAttr
-	err := dec.ExpectList(func() error {
-		attr, err := ExpectMailboxAttr(dec)
-		if err != nil {
-			return err
-		}
-		attrs = append(attrs, attr)
-		return nil
-	})
-	return attrs, err
-}
-
-func ExpectMailboxAttr(dec *imapwire.Decoder) (imap.MailboxAttr, error) {
-	flag, err := ExpectFlag(dec)
-	return canonicalMailboxAttr(string(flag)), err
-}
-
-var (
-	canonOnce        sync.Once
-	canonFlag        map[string]imap.Flag
-	canonMailboxAttr map[string]imap.MailboxAttr
-)
-
-func canonInit() {
-	flags := []imap.Flag{
-		imap.FlagSeen,
-		imap.FlagAnswered,
-		imap.FlagFlagged,
-		imap.FlagDeleted,
-		imap.FlagDraft,
-		imap.FlagForwarded,
-		imap.FlagMDNSent,
-		imap.FlagJunk,
-		imap.FlagNotJunk,
-		imap.FlagPhishing,
-		imap.FlagImportant,
-	}
-	mailboxAttrs := []imap.MailboxAttr{
-		imap.MailboxAttrNonExistent,
-		imap.MailboxAttrNoInferiors,
-		imap.MailboxAttrNoSelect,
-		imap.MailboxAttrHasChildren,
-		imap.MailboxAttrHasNoChildren,
-		imap.MailboxAttrMarked,
-		imap.MailboxAttrUnmarked,
-		imap.MailboxAttrSubscribed,
-		imap.MailboxAttrRemote,
-		imap.MailboxAttrAll,
-		imap.MailboxAttrArchive,
-		imap.MailboxAttrDrafts,
-		imap.MailboxAttrFlagged,
-		imap.MailboxAttrJunk,
-		imap.MailboxAttrSent,
-		imap.MailboxAttrTrash,
-		imap.MailboxAttrImportant,
-	}
-
-	canonFlag = make(map[string]imap.Flag)
-	for _, flag := range flags {
-		canonFlag[strings.ToLower(string(flag))] = flag
-	}
-
-	canonMailboxAttr = make(map[string]imap.MailboxAttr)
-	for _, attr := range mailboxAttrs {
-		canonMailboxAttr[strings.ToLower(string(attr))] = attr
-	}
-}
-
-func canonicalFlag(s string) imap.Flag {
-	canonOnce.Do(canonInit)
-	if flag, ok := canonFlag[strings.ToLower(s)]; ok {
-		return flag
-	}
-	return imap.Flag(s)
-}
-
-func canonicalMailboxAttr(s string) imap.MailboxAttr {
-	canonOnce.Do(canonInit)
-	if attr, ok := canonMailboxAttr[strings.ToLower(s)]; ok {
-		return attr
-	}
-	return imap.MailboxAttr(s)
-}

internal/sasl.go

@@ -1,23 +0,0 @@
-package internal
-
-import (
-	"encoding/base64"
-)
-
-func EncodeSASL(b []byte) string {
-	if len(b) == 0 {
-		return "="
-	} else {
-		return base64.StdEncoding.EncodeToString(b)
-	}
-}
-
-func DecodeSASL(s string) ([]byte, error) {
-	if s == "=" {
-		// go-sasl treats nil as no challenge/response, so return a non-nil
-		// empty byte slice
-		return []byte{}, nil
-	} else {
-		return base64.StdEncoding.DecodeString(s)
-	}
-}

internal/testcert.go

@@ -0,0 +1,37 @@
+package internal
+
+// LocalhostCert is a PEM-encoded TLS cert with SAN IPs
+// "127.0.0.1" and "[::1]", expiring at Jan 29 16:00:00 2084 GMT.
+// generated from src/crypto/tls:
+// go run generate_cert.go  --rsa-bits 1024 --host 127.0.0.1,::1,example.com --ca --start-date "Jan 1 00:00:00 1970" --duration=1000000h
+var LocalhostCert = []byte(`-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----`)
+
+// LocalhostKey is the private key for localhostCert.
+var LocalhostKey = []byte(`-----BEGIN RSA PRIVATE KEY-----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+-----END RSA PRIVATE KEY-----`)

internal/testutil.go

@@ -0,0 +1,16 @@
+package internal
+
+type MapListSorter []interface{}
+
+func (s MapListSorter) Len() int {
+	return len(s) / 2
+}
+
+func (s MapListSorter) Less(i, j int) bool {
+	return s[i*2].(string) < s[j*2].(string)
+}
+
+func (s MapListSorter) Swap(i, j int) {
+	s[i*2], s[j*2] = s[j*2], s[i*2]
+	s[i*2+1], s[j*2+1] = s[j*2+1], s[i*2+1]
+}

internal/utf7/utf7.go

@@ -1,13 +0,0 @@
-// Package utf7 implements modified UTF-7 encoding defined in RFC 3501 section 5.1.3
-package utf7
-
-import (
-	"encoding/base64"
-)
-
-const (
-	min = 0x20 // Minimum self-representing UTF-7 value
-	max = 0x7E // Maximum self-representing UTF-7 value
-)
-
-var b64Enc = base64.NewEncoding("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,")

literal.go

@@ -0,0 +1,13 @@
+package imap
+
+import (
+	"io"
+)
+
+// A literal, as defined in RFC 3501 section 4.3.
+type Literal interface {
+	io.Reader
+
+	// Len returns the number of bytes of the literal.
+	Len() int
+}

logger.go

@@ -0,0 +1,8 @@
+package imap
+
+// Logger is the behaviour used by server/client to
+// report errors for accepting connections and unexpected behavior from handlers.
+type Logger interface {
+	Printf(format string, v ...interface{})
+	Println(v ...interface{})
+}

mailbox.go

@@ -0,0 +1,314 @@
+package imap
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+	"sync"
+
+	"github.com/emersion/go-imap/utf7"
+)
+
+// The primary mailbox, as defined in RFC 3501 section 5.1.
+const InboxName = "INBOX"
+
+// CanonicalMailboxName returns the canonical form of a mailbox name. Mailbox names can be
+// case-sensitive or case-insensitive depending on the backend implementation.
+// The special INBOX mailbox is case-insensitive.
+func CanonicalMailboxName(name string) string {
+	if strings.EqualFold(name, InboxName) {
+		return InboxName
+	}
+	return name
+}
+
+// Mailbox attributes definied in RFC 3501 section 7.2.2.
+const (
+	// It is not possible for any child levels of hierarchy to exist under this\
+	// name; no child levels exist now and none can be created in the future.
+	NoInferiorsAttr = "\\Noinferiors"
+	// It is not possible to use this name as a selectable mailbox.
+	NoSelectAttr = "\\Noselect"
+	// The mailbox has been marked "interesting" by the server; the mailbox
+	// probably contains messages that have been added since the last time the
+	// mailbox was selected.
+	MarkedAttr = "\\Marked"
+	// The mailbox does not contain any additional messages since the last time
+	// the mailbox was selected.
+	UnmarkedAttr = "\\Unmarked"
+)
+
+// Mailbox attributes defined in RFC 6154 section 2 (SPECIAL-USE extension).
+const (
+	// This mailbox presents all messages in the user's message store.
+	AllAttr = "\\All"
+	// This mailbox is used to archive messages.
+	ArchiveAttr = "\\Archive"
+	// This mailbox is used to hold draft messages -- typically, messages that are
+	// being composed but have not yet been sent.
+	DraftsAttr = "\\Drafts"
+	// This mailbox presents all messages marked in some way as "important".
+	FlaggedAttr = "\\Flagged"
+	// This mailbox is where messages deemed to be junk mail are held.
+	JunkAttr = "\\Junk"
+	// This mailbox is used to hold copies of messages that have been sent.
+	SentAttr = "\\Sent"
+	// This mailbox is used to hold messages that have been deleted or marked for
+	// deletion.
+	TrashAttr = "\\Trash"
+)
+
+// Mailbox attributes defined in RFC 3348 (CHILDREN extension)
+const (
+	// The presence of this attribute indicates that the mailbox has child
+	// mailboxes.
+	HasChildrenAttr = "\\HasChildren"
+	// The presence of this attribute indicates that the mailbox has no child
+	// mailboxes.
+	HasNoChildrenAttr = "\\HasNoChildren"
+)
+
+// This mailbox attribute is a signal that the mailbox contains messages that
+// are likely important to the user. This attribute is defined in RFC 8457
+// section 3.
+const ImportantAttr = "\\Important"
+
+// Basic mailbox info.
+type MailboxInfo struct {
+	// The mailbox attributes.
+	Attributes []string
+	// The server's path separator.
+	Delimiter string
+	// The mailbox name.
+	Name string
+}
+
+// Parse mailbox info from fields.
+func (info *MailboxInfo) Parse(fields []interface{}) error {
+	if len(fields) < 3 {
+		return errors.New("Mailbox info needs at least 3 fields")
+	}
+
+	var err error
+	if info.Attributes, err = ParseStringList(fields[0]); err != nil {
+		return err
+	}
+
+	var ok bool
+	if info.Delimiter, ok = fields[1].(string); !ok {
+		// The delimiter may be specified as NIL, which gets converted to a nil interface.
+		if fields[1] != nil {
+			return errors.New("Mailbox delimiter must be a string")
+		}
+		info.Delimiter = ""
+	}
+
+	if name, err := ParseString(fields[2]); err != nil {
+		return err
+	} else if name, err := utf7.Encoding.NewDecoder().String(name); err != nil {
+		return err
+	} else {
+		info.Name = CanonicalMailboxName(name)
+	}
+
+	return nil
+}
+
+// Format mailbox info to fields.
+func (info *MailboxInfo) Format() []interface{} {
+	name, _ := utf7.Encoding.NewEncoder().String(info.Name)
+	attrs := make([]interface{}, len(info.Attributes))
+	for i, attr := range info.Attributes {
+		attrs[i] = RawString(attr)
+	}
+
+	// If the delimiter is NIL, we need to treat it specially by inserting
+	// a nil field (so that it's later converted to an unquoted NIL atom).
+	var del interface{}
+
+	if info.Delimiter != "" {
+		del = info.Delimiter
+	}
+
+	// Thunderbird doesn't understand delimiters if not quoted
+	return []interface{}{attrs, del, FormatMailboxName(name)}
+}
+
+// TODO: optimize this
+func (info *MailboxInfo) match(name, pattern string) bool {
+	i := strings.IndexAny(pattern, "*%")
+	if i == -1 {
+		// No more wildcards
+		return name == pattern
+	}
+
+	// Get parts before and after wildcard
+	chunk, wildcard, rest := pattern[0:i], pattern[i], pattern[i+1:]
+
+	// Check that name begins with chunk
+	if len(chunk) > 0 && !strings.HasPrefix(name, chunk) {
+		return false
+	}
+	name = strings.TrimPrefix(name, chunk)
+
+	// Expand wildcard
+	var j int
+	for j = 0; j < len(name); j++ {
+		if wildcard == '%' && string(name[j]) == info.Delimiter {
+			break // Stop on delimiter if wildcard is %
+		}
+		// Try to match the rest from here
+		if info.match(name[j:], rest) {
+			return true
+		}
+	}
+
+	return info.match(name[j:], rest)
+}
+
+// Match checks if a reference and a pattern matches this mailbox name, as
+// defined in RFC 3501 section 6.3.8.
+func (info *MailboxInfo) Match(reference, pattern string) bool {
+	name := info.Name
+
+	if info.Delimiter != "" && strings.HasPrefix(pattern, info.Delimiter) {
+		reference = ""
+		pattern = strings.TrimPrefix(pattern, info.Delimiter)
+	}
+	if reference != "" {
+		if info.Delimiter != "" && !strings.HasSuffix(reference, info.Delimiter) {
+			reference += info.Delimiter
+		}
+		if !strings.HasPrefix(name, reference) {
+			return false
+		}
+		name = strings.TrimPrefix(name, reference)
+	}
+
+	return info.match(name, pattern)
+}
+
+// A mailbox status.
+type MailboxStatus struct {
+	// The mailbox name.
+	Name string
+	// True if the mailbox is open in read-only mode.
+	ReadOnly bool
+	// The mailbox items that are currently filled in. This map's values
+	// should not be used directly, they must only be used by libraries
+	// implementing extensions of the IMAP protocol.
+	Items map[StatusItem]interface{}
+
+	// The Items map may be accessed in different goroutines. Protect
+	// concurrent writes.
+	ItemsLocker sync.Mutex
+
+	// The mailbox flags.
+	Flags []string
+	// The mailbox permanent flags.
+	PermanentFlags []string
+	// The sequence number of the first unseen message in the mailbox.
+	UnseenSeqNum uint32
+
+	// The number of messages in this mailbox.
+	Messages uint32
+	// The number of messages not seen since the last time the mailbox was opened.
+	Recent uint32
+	// The number of unread messages.
+	Unseen uint32
+	// The next UID.
+	UidNext uint32
+	// Together with a UID, it is a unique identifier for a message.
+	// Must be greater than or equal to 1.
+	UidValidity uint32
+
+	// Per-mailbox limit of message size. Set only if server supports the
+	// APPENDLIMIT extension.
+	AppendLimit uint32
+}
+
+// Create a new mailbox status that will contain the specified items.
+func NewMailboxStatus(name string, items []StatusItem) *MailboxStatus {
+	status := &MailboxStatus{
+		Name:  name,
+		Items: make(map[StatusItem]interface{}),
+	}
+
+	for _, k := range items {
+		status.Items[k] = nil
+	}
+
+	return status
+}
+
+func (status *MailboxStatus) Parse(fields []interface{}) error {
+	status.Items = make(map[StatusItem]interface{})
+
+	var k StatusItem
+	for i, f := range fields {
+		if i%2 == 0 {
+			if kstr, ok := f.(string); !ok {
+				return fmt.Errorf("cannot parse mailbox status: key is not a string, but a %T", f)
+			} else {
+				k = StatusItem(strings.ToUpper(kstr))
+			}
+		} else {
+			status.Items[k] = nil
+
+			var err error
+			switch k {
+			case StatusMessages:
+				status.Messages, err = ParseNumber(f)
+			case StatusRecent:
+				status.Recent, err = ParseNumber(f)
+			case StatusUnseen:
+				status.Unseen, err = ParseNumber(f)
+			case StatusUidNext:
+				status.UidNext, err = ParseNumber(f)
+			case StatusUidValidity:
+				status.UidValidity, err = ParseNumber(f)
+			case StatusAppendLimit:
+				status.AppendLimit, err = ParseNumber(f)
+			default:
+				status.Items[k] = f
+			}
+
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+func (status *MailboxStatus) Format() []interface{} {
+	var fields []interface{}
+	for k, v := range status.Items {
+		switch k {
+		case StatusMessages:
+			v = status.Messages
+		case StatusRecent:
+			v = status.Recent
+		case StatusUnseen:
+			v = status.Unseen
+		case StatusUidNext:
+			v = status.UidNext
+		case StatusUidValidity:
+			v = status.UidValidity
+		case StatusAppendLimit:
+			v = status.AppendLimit
+		}
+
+		fields = append(fields, RawString(k), v)
+	}
+	return fields
+}
+
+func FormatMailboxName(name string) interface{} {
+	// Some e-mails servers don't handle quoted INBOX names correctly so we special-case it.
+	if strings.EqualFold(name, "INBOX") {
+		return RawString(name)
+	}
+	return name
+}

mailbox_test.go

@@ -0,0 +1,191 @@
+package imap_test
+
+import (
+	"fmt"
+	"reflect"
+	"sort"
+	"testing"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/internal"
+)
+
+func TestCanonicalMailboxName(t *testing.T) {
+	if got := imap.CanonicalMailboxName("Inbox"); got != imap.InboxName {
+		t.Errorf("Invalid canonical mailbox name: expected %q but got %q", imap.InboxName, got)
+	}
+	if got := imap.CanonicalMailboxName("Drafts"); got != "Drafts" {
+		t.Errorf("Invalid canonical mailbox name: expected %q but got %q", "Drafts", got)
+	}
+}
+
+var mailboxInfoTests = []struct {
+	fields []interface{}
+	info   *imap.MailboxInfo
+}{
+	{
+		fields: []interface{}{
+			[]interface{}{"\\Noselect", "\\Recent", "\\Unseen"},
+			"/",
+			"INBOX",
+		},
+		info: &imap.MailboxInfo{
+			Attributes: []string{"\\Noselect", "\\Recent", "\\Unseen"},
+			Delimiter:  "/",
+			Name:       "INBOX",
+		},
+	},
+}
+
+func TestMailboxInfo_Parse(t *testing.T) {
+	for _, test := range mailboxInfoTests {
+		info := &imap.MailboxInfo{}
+		if err := info.Parse(test.fields); err != nil {
+			t.Fatal(err)
+		}
+
+		if fmt.Sprint(info.Attributes) != fmt.Sprint(test.info.Attributes) {
+			t.Fatal("Invalid flags:", info.Attributes)
+		}
+		if info.Delimiter != test.info.Delimiter {
+			t.Fatal("Invalid delimiter:", info.Delimiter)
+		}
+		if info.Name != test.info.Name {
+			t.Fatal("Invalid name:", info.Name)
+		}
+	}
+}
+
+func TestMailboxInfo_Format(t *testing.T) {
+	for _, test := range mailboxInfoTests {
+		fields := test.info.Format()
+
+		if fmt.Sprint(fields) != fmt.Sprint(test.fields) {
+			t.Fatal("Invalid fields:", fields)
+		}
+	}
+}
+
+var mailboxInfoMatchTests = []struct {
+	name, ref, pattern string
+	result             bool
+}{
+	{name: "INBOX", pattern: "INBOX", result: true},
+	{name: "INBOX", pattern: "Asuka", result: false},
+	{name: "INBOX", pattern: "*", result: true},
+	{name: "INBOX", pattern: "%", result: true},
+	{name: "Neon Genesis Evangelion/Misato", pattern: "*", result: true},
+	{name: "Neon Genesis Evangelion/Misato", pattern: "%", result: false},
+	{name: "Neon Genesis Evangelion/Misato", pattern: "Neon Genesis Evangelion/*", result: true},
+	{name: "Neon Genesis Evangelion/Misato", pattern: "Neon Genesis Evangelion/%", result: true},
+	{name: "Neon Genesis Evangelion/Misato", pattern: "Neo* Evangelion/Misato", result: true},
+	{name: "Neon Genesis Evangelion/Misato", pattern: "Neo% Evangelion/Misato", result: true},
+	{name: "Neon Genesis Evangelion/Misato", pattern: "*Eva*/Misato", result: true},
+	{name: "Neon Genesis Evangelion/Misato", pattern: "%Eva%/Misato", result: true},
+	{name: "Neon Genesis Evangelion/Misato", pattern: "*X*/Misato", result: false},
+	{name: "Neon Genesis Evangelion/Misato", pattern: "%X%/Misato", result: false},
+	{name: "Neon Genesis Evangelion/Misato", pattern: "Neon Genesis Evangelion/Mi%o", result: true},
+	{name: "Neon Genesis Evangelion/Misato", pattern: "Neon Genesis Evangelion/Mi%too", result: false},
+	{name: "Misato/Misato", pattern: "Mis*to/Misato", result: true},
+	{name: "Misato/Misato", pattern: "Mis*to", result: true},
+	{name: "Misato/Misato/Misato", pattern: "Mis*to/Mis%to", result: true},
+	{name: "Misato/Misato", pattern: "Mis**to/Misato", result: true},
+	{name: "Misato/Misato", pattern: "Misat%/Misato", result: true},
+	{name: "Misato/Misato", pattern: "Misat%Misato", result: false},
+	{name: "Misato/Misato", ref: "Misato", pattern: "Misato", result: true},
+	{name: "Misato/Misato", ref: "Misato/", pattern: "Misato", result: true},
+	{name: "Misato/Misato", ref: "Shinji", pattern: "/Misato/*", result: true},
+	{name: "Misato/Misato", ref: "Misato", pattern: "/Misato", result: false},
+	{name: "Misato/Misato", ref: "Misato", pattern: "Shinji", result: false},
+	{name: "Misato/Misato", ref: "Shinji", pattern: "Misato", result: false},
+}
+
+func TestMailboxInfo_Match(t *testing.T) {
+	for _, test := range mailboxInfoMatchTests {
+		info := &imap.MailboxInfo{Name: test.name, Delimiter: "/"}
+		result := info.Match(test.ref, test.pattern)
+		if result != test.result {
+			t.Errorf("Matching name %q with pattern %q and reference %q returns %v, but expected %v", test.name, test.pattern, test.ref, result, test.result)
+		}
+	}
+}
+
+func TestNewMailboxStatus(t *testing.T) {
+	status := imap.NewMailboxStatus("INBOX", []imap.StatusItem{imap.StatusMessages, imap.StatusUnseen})
+
+	expected := &imap.MailboxStatus{
+		Name:  "INBOX",
+		Items: map[imap.StatusItem]interface{}{imap.StatusMessages: nil, imap.StatusUnseen: nil},
+	}
+
+	if !reflect.DeepEqual(expected, status) {
+		t.Errorf("Invalid mailbox status: expected \n%+v\n but got \n%+v", expected, status)
+	}
+}
+
+var mailboxStatusTests = [...]struct {
+	fields []interface{}
+	status *imap.MailboxStatus
+}{
+	{
+		fields: []interface{}{
+			"MESSAGES", uint32(42),
+			"RECENT", uint32(1),
+			"UNSEEN", uint32(6),
+			"UIDNEXT", uint32(65536),
+			"UIDVALIDITY", uint32(4242),
+		},
+		status: &imap.MailboxStatus{
+			Items: map[imap.StatusItem]interface{}{
+				imap.StatusMessages:    nil,
+				imap.StatusRecent:      nil,
+				imap.StatusUnseen:      nil,
+				imap.StatusUidNext:     nil,
+				imap.StatusUidValidity: nil,
+			},
+			Messages:    42,
+			Recent:      1,
+			Unseen:      6,
+			UidNext:     65536,
+			UidValidity: 4242,
+		},
+	},
+}
+
+func TestMailboxStatus_Parse(t *testing.T) {
+	for i, test := range mailboxStatusTests {
+		status := &imap.MailboxStatus{}
+		if err := status.Parse(test.fields); err != nil {
+			t.Errorf("Expected no error while parsing mailbox status #%v, got: %v", i, err)
+			continue
+		}
+
+		if !reflect.DeepEqual(status, test.status) {
+			t.Errorf("Invalid parsed mailbox status for #%v: got \n%+v\n but expected \n%+v", i, status, test.status)
+		}
+	}
+}
+
+func TestMailboxStatus_Format(t *testing.T) {
+	for i, test := range mailboxStatusTests {
+		fields := test.status.Format()
+
+		// MapListSorter does not know about RawString and will panic.
+		stringFields := make([]interface{}, 0, len(fields))
+		for _, field := range fields {
+			if s, ok := field.(imap.RawString); ok {
+				stringFields = append(stringFields, string(s))
+			} else {
+				stringFields = append(stringFields, field)
+			}
+		}
+
+		sort.Sort(internal.MapListSorter(stringFields))
+
+		sort.Sort(internal.MapListSorter(test.fields))
+
+		if !reflect.DeepEqual(stringFields, test.fields) {
+			t.Errorf("Invalid mailbox status fields for #%v: got \n%+v\n but expected \n%+v", i, fields, test.fields)
+		}
+	}
+}

message_test.go

@@ -0,0 +1,797 @@
+package imap
+
+import (
+	"bytes"
+	"fmt"
+	"reflect"
+	"testing"
+	"time"
+)
+
+func TestCanonicalFlag(t *testing.T) {
+	if got := CanonicalFlag("\\SEEN"); got != SeenFlag {
+		t.Errorf("Invalid canonical flag: expected %q but got %q", SeenFlag, got)
+	}
+
+	if got := CanonicalFlag("Junk"); got != "junk" {
+		t.Errorf("Invalid canonical flag: expected %q but got %q", "junk", got)
+	}
+}
+
+func TestNewMessage(t *testing.T) {
+	msg := NewMessage(42, []FetchItem{FetchBodyStructure, FetchFlags})
+
+	expected := &Message{
+		SeqNum:     42,
+		Items:      map[FetchItem]interface{}{FetchBodyStructure: nil, FetchFlags: nil},
+		Body:       make(map[*BodySectionName]Literal),
+		itemsOrder: []FetchItem{FetchBodyStructure, FetchFlags},
+	}
+
+	if !reflect.DeepEqual(expected, msg) {
+		t.Errorf("Invalid message: expected \n%+v\n but got \n%+v", expected, msg)
+	}
+}
+
+func formatFields(fields []interface{}) (string, error) {
+	b := &bytes.Buffer{}
+	w := NewWriter(b)
+
+	if err := w.writeList(fields); err != nil {
+		return "", fmt.Errorf("Cannot format \n%+v\n got error: \n%v", fields, err)
+	}
+
+	return b.String(), nil
+}
+
+var messageTests = []struct {
+	message *Message
+	fields  []interface{}
+}{
+	{
+		message: &Message{
+			Items: map[FetchItem]interface{}{
+				FetchEnvelope:   nil,
+				FetchBody:       nil,
+				FetchFlags:      nil,
+				FetchRFC822Size: nil,
+				FetchUid:        nil,
+			},
+			Body:          map[*BodySectionName]Literal{},
+			Envelope:      envelopeTests[0].envelope,
+			BodyStructure: bodyStructureTests[0].bodyStructure,
+			Flags:         []string{SeenFlag, AnsweredFlag},
+			Size:          4242,
+			Uid:           2424,
+			itemsOrder:    []FetchItem{FetchEnvelope, FetchBody, FetchFlags, FetchRFC822Size, FetchUid},
+		},
+		fields: []interface{}{
+			RawString("ENVELOPE"), envelopeTests[0].fields,
+			RawString("BODY"), bodyStructureTests[0].fields,
+			RawString("FLAGS"), []interface{}{RawString(SeenFlag), RawString(AnsweredFlag)},
+			RawString("RFC822.SIZE"), RawString("4242"),
+			RawString("UID"), RawString("2424"),
+		},
+	},
+}
+
+func TestMessage_Parse(t *testing.T) {
+	for i, test := range messageTests {
+		m := &Message{}
+		if err := m.Parse(test.fields); err != nil {
+			t.Errorf("Cannot parse message for #%v: %v", i, err)
+		} else if !reflect.DeepEqual(m, test.message) {
+			t.Errorf("Invalid parsed message for #%v: got \n%+v\n but expected \n%+v", i, m, test.message)
+		}
+	}
+}
+
+func TestMessage_Format(t *testing.T) {
+	for i, test := range messageTests {
+		fields := test.message.Format()
+
+		got, err := formatFields(fields)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+
+		expected, _ := formatFields(test.fields)
+
+		if got != expected {
+			t.Errorf("Invalid message fields for #%v: got \n%v\n but expected \n%v", i, got, expected)
+		}
+	}
+}
+
+var bodySectionNameTests = []struct {
+	raw       string
+	parsed    *BodySectionName
+	formatted string
+}{
+	{
+		raw:    "BODY[]",
+		parsed: &BodySectionName{BodyPartName: BodyPartName{}},
+	},
+	{
+		raw:       "RFC822",
+		parsed:    &BodySectionName{BodyPartName: BodyPartName{}},
+		formatted: "BODY[]",
+	},
+	{
+		raw:    "BODY[HEADER]",
+		parsed: &BodySectionName{BodyPartName: BodyPartName{Specifier: HeaderSpecifier}},
+	},
+	{
+		raw:    "BODY.PEEK[]",
+		parsed: &BodySectionName{BodyPartName: BodyPartName{}, Peek: true},
+	},
+	{
+		raw:    "BODY[TEXT]",
+		parsed: &BodySectionName{BodyPartName: BodyPartName{Specifier: TextSpecifier}},
+	},
+	{
+		raw:       "RFC822.TEXT",
+		parsed:    &BodySectionName{BodyPartName: BodyPartName{Specifier: TextSpecifier}},
+		formatted: "BODY[TEXT]",
+	},
+	{
+		raw:       "RFC822.HEADER",
+		parsed:    &BodySectionName{BodyPartName: BodyPartName{Specifier: HeaderSpecifier}, Peek: true},
+		formatted: "BODY.PEEK[HEADER]",
+	},
+	{
+		raw:    "BODY[]<0.512>",
+		parsed: &BodySectionName{BodyPartName: BodyPartName{}, Partial: []int{0, 512}},
+	},
+	{
+		raw:    "BODY[]<512>",
+		parsed: &BodySectionName{BodyPartName: BodyPartName{}, Partial: []int{512}},
+	},
+	{
+		raw:    "BODY[1.2.3]",
+		parsed: &BodySectionName{BodyPartName: BodyPartName{Path: []int{1, 2, 3}}},
+	},
+	{
+		raw:    "BODY[1.2.3.HEADER]",
+		parsed: &BodySectionName{BodyPartName: BodyPartName{Specifier: HeaderSpecifier, Path: []int{1, 2, 3}}},
+	},
+	{
+		raw:    "BODY[5.MIME]",
+		parsed: &BodySectionName{BodyPartName: BodyPartName{Specifier: MIMESpecifier, Path: []int{5}}},
+	},
+	{
+		raw:    "BODY[HEADER.FIELDS (From To)]",
+		parsed: &BodySectionName{BodyPartName: BodyPartName{Specifier: HeaderSpecifier, Fields: []string{"From", "To"}}},
+	},
+	{
+		raw:    "BODY[HEADER.FIELDS.NOT (Content-Id)]",
+		parsed: &BodySectionName{BodyPartName: BodyPartName{Specifier: HeaderSpecifier, Fields: []string{"Content-Id"}, NotFields: true}},
+	},
+}
+
+func TestNewBodySectionName(t *testing.T) {
+	for i, test := range bodySectionNameTests {
+		bsn, err := ParseBodySectionName(FetchItem(test.raw))
+		if err != nil {
+			t.Errorf("Cannot parse #%v: %v", i, err)
+			continue
+		}
+
+		if !reflect.DeepEqual(bsn.BodyPartName, test.parsed.BodyPartName) {
+			t.Errorf("Invalid body part name for #%v: %#+v", i, bsn.BodyPartName)
+		} else if bsn.Peek != test.parsed.Peek {
+			t.Errorf("Invalid peek value for #%v: %#+v", i, bsn.Peek)
+		} else if !reflect.DeepEqual(bsn.Partial, test.parsed.Partial) {
+			t.Errorf("Invalid partial for #%v: %#+v", i, bsn.Partial)
+		}
+	}
+}
+
+func TestBodySectionName_String(t *testing.T) {
+	for i, test := range bodySectionNameTests {
+		s := string(test.parsed.FetchItem())
+
+		expected := test.formatted
+		if expected == "" {
+			expected = test.raw
+		}
+
+		if expected != s {
+			t.Errorf("Invalid body section name for #%v: got %v but expected %v", i, s, expected)
+		}
+	}
+}
+
+func TestBodySectionName_ExtractPartial(t *testing.T) {
+	tests := []struct {
+		bsn     string
+		whole   string
+		partial string
+	}{
+		{
+			bsn:     "BODY[]",
+			whole:   "Hello World!",
+			partial: "Hello World!",
+		},
+		{
+			bsn:     "BODY[]<6.5>",
+			whole:   "Hello World!",
+			partial: "World",
+		},
+		{
+			bsn:     "BODY[]<6.1000>",
+			whole:   "Hello World!",
+			partial: "World!",
+		},
+		{
+			bsn:     "BODY[]<0.1>",
+			whole:   "Hello World!",
+			partial: "H",
+		},
+		{
+			bsn:     "BODY[]<1000.2000>",
+			whole:   "Hello World!",
+			partial: "",
+		},
+	}
+
+	for i, test := range tests {
+		bsn, err := ParseBodySectionName(FetchItem(test.bsn))
+		if err != nil {
+			t.Errorf("Cannot parse body section name #%v: %v", i, err)
+			continue
+		}
+
+		partial := string(bsn.ExtractPartial([]byte(test.whole)))
+		if partial != test.partial {
+			t.Errorf("Invalid partial for #%v: got %v but expected %v", i, partial, test.partial)
+		}
+	}
+}
+
+var t = time.Date(2009, time.November, 10, 23, 0, 0, 0, time.FixedZone("", -6*60*60))
+
+var envelopeTests = []struct {
+	envelope *Envelope
+	fields   []interface{}
+}{
+	{
+		envelope: &Envelope{
+			Date:      t,
+			Subject:   "Hello World!",
+			From:      []*Address{addrTests[0].addr},
+			Sender:    nil,
+			ReplyTo:   nil,
+			To:        nil,
+			Cc:        nil,
+			Bcc:       nil,
+			InReplyTo: "42@example.org",
+			MessageId: "43@example.org",
+		},
+		fields: []interface{}{
+			"Tue, 10 Nov 2009 23:00:00 -0600",
+			"Hello World!",
+			[]interface{}{addrTests[0].fields},
+			nil,
+			nil,
+			nil,
+			nil,
+			nil,
+			"42@example.org",
+			"43@example.org",
+		},
+	},
+}
+
+func TestEnvelope_Parse(t *testing.T) {
+	for i, test := range envelopeTests {
+		e := &Envelope{}
+		if err := e.Parse(test.fields); err != nil {
+			t.Error("Error parsing envelope:", err)
+		} else if !reflect.DeepEqual(e, test.envelope) {
+			t.Errorf("Invalid envelope for #%v: got %v but expected %v", i, e, test.envelope)
+		}
+	}
+}
+
+func TestEnvelope_Parse_literal(t *testing.T) {
+	subject := "Hello World!"
+	l := bytes.NewBufferString(subject)
+	fields := []interface{}{
+		"Tue, 10 Nov 2009 23:00:00 -0600",
+		l,
+		nil,
+		nil,
+		nil,
+		nil,
+		nil,
+		nil,
+		"42@example.org",
+		"43@example.org",
+	}
+
+	e := &Envelope{}
+	if err := e.Parse(fields); err != nil {
+		t.Error("Error parsing envelope:", err)
+	} else if e.Subject != subject {
+		t.Errorf("Invalid envelope subject: got %v but expected %v", e.Subject, subject)
+	}
+}
+
+func TestEnvelope_Format(t *testing.T) {
+	for i, test := range envelopeTests {
+		fields := test.envelope.Format()
+
+		got, err := formatFields(fields)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+
+		expected, _ := formatFields(test.fields)
+
+		if got != expected {
+			t.Errorf("Invalid envelope fields for #%v: got %v but expected %v", i, got, expected)
+		}
+	}
+}
+
+var addrTests = []struct {
+	fields []interface{}
+	addr   *Address
+}{
+	{
+		fields: []interface{}{"The NSA", nil, "root", "nsa.gov"},
+		addr: &Address{
+			PersonalName: "The NSA",
+			MailboxName:  "root",
+			HostName:     "nsa.gov",
+		},
+	},
+}
+
+func TestAddress_Parse(t *testing.T) {
+	for i, test := range addrTests {
+		addr := &Address{}
+
+		if err := addr.Parse(test.fields); err != nil {
+			t.Error("Error parsing address:", err)
+		} else if !reflect.DeepEqual(addr, test.addr) {
+			t.Errorf("Invalid address for #%v: got %v but expected %v", i, addr, test.addr)
+		}
+	}
+}
+
+func TestAddress_Format(t *testing.T) {
+	for i, test := range addrTests {
+		fields := test.addr.Format()
+		if !reflect.DeepEqual(fields, test.fields) {
+			t.Errorf("Invalid address fields for #%v: got %v but expected %v", i, fields, test.fields)
+		}
+	}
+}
+
+func TestEmptyAddress(t *testing.T) {
+	fields := []interface{}{nil, nil, nil, nil}
+	addr := &Address{}
+	err := addr.Parse(fields)
+	if err == nil {
+		t.Error("A nil address did not return an error")
+	}
+}
+
+func TestEmptyGroupAddress(t *testing.T) {
+	fields := []interface{}{nil, nil, "undisclosed-recipients", nil}
+	addr := &Address{}
+	err := addr.Parse(fields)
+	if err == nil {
+		t.Error("An empty group did not return an error when parsed as address")
+	}
+}
+
+func TestAddressList(t *testing.T) {
+	fields := make([]interface{}, len(addrTests))
+	addrs := make([]*Address, len(addrTests))
+	for i, test := range addrTests {
+		fields[i] = test.fields
+		addrs[i] = test.addr
+	}
+
+	gotAddrs := ParseAddressList(fields)
+	if !reflect.DeepEqual(gotAddrs, addrs) {
+		t.Error("Invalid address list: got", gotAddrs, "but expected", addrs)
+	}
+
+	gotFields := FormatAddressList(addrs)
+	if !reflect.DeepEqual(gotFields, fields) {
+		t.Error("Invalid address list fields: got", gotFields, "but expected", fields)
+	}
+}
+
+func TestEmptyAddressList(t *testing.T) {
+	addrs := make([]*Address, 0)
+
+	gotFields := FormatAddressList(addrs)
+	if !reflect.DeepEqual(gotFields, nil) {
+		t.Error("Invalid address list fields: got", gotFields, "but expected nil")
+	}
+}
+
+var paramsListTest = []struct {
+	fields []interface{}
+	params map[string]string
+}{
+	{
+		fields: nil,
+		params: map[string]string{},
+	},
+	{
+		fields: []interface{}{"a", "b"},
+		params: map[string]string{"a": "b"},
+	},
+}
+
+func TestParseParamList(t *testing.T) {
+	for i, test := range paramsListTest {
+		if params, err := ParseParamList(test.fields); err != nil {
+			t.Errorf("Cannot parse params fields for #%v: %v", i, err)
+		} else if !reflect.DeepEqual(params, test.params) {
+			t.Errorf("Invalid params for #%v: got %v but expected %v", i, params, test.params)
+		}
+	}
+
+	// Malformed params lists
+
+	fields := []interface{}{"cc", []interface{}{"dille"}}
+	if params, err := ParseParamList(fields); err == nil {
+		t.Error("Parsed invalid params list:", params)
+	}
+
+	fields = []interface{}{"cc"}
+	if params, err := ParseParamList(fields); err == nil {
+		t.Error("Parsed invalid params list:", params)
+	}
+}
+
+func TestFormatParamList(t *testing.T) {
+	for i, test := range paramsListTest {
+		fields := FormatParamList(test.params)
+
+		if !reflect.DeepEqual(fields, test.fields) {
+			t.Errorf("Invalid params fields for #%v: got %v but expected %v", i, fields, test.fields)
+		}
+	}
+}
+
+var bodyStructureTests = []struct {
+	fields        []interface{}
+	bodyStructure *BodyStructure
+}{
+	{
+		fields: []interface{}{"image", "jpeg", []interface{}{}, "<foo4%25foo1@bar.net>", "A picture of cat", "base64", RawString("4242")},
+		bodyStructure: &BodyStructure{
+			MIMEType:    "image",
+			MIMESubType: "jpeg",
+			Params:      map[string]string{},
+			Id:          "<foo4%25foo1@bar.net>",
+			Description: "A picture of cat",
+			Encoding:    "base64",
+			Size:        4242,
+		},
+	},
+	{
+		fields: []interface{}{"text", "plain", []interface{}{"charset", "utf-8"}, nil, nil, "us-ascii", RawString("42"), RawString("2")},
+		bodyStructure: &BodyStructure{
+			MIMEType:    "text",
+			MIMESubType: "plain",
+			Params:      map[string]string{"charset": "utf-8"},
+			Encoding:    "us-ascii",
+			Size:        42,
+			Lines:       2,
+		},
+	},
+	{
+		fields: []interface{}{
+			"message", "rfc822", []interface{}{}, nil, nil, "us-ascii", RawString("42"),
+			(&Envelope{}).Format(),
+			(&BodyStructure{}).Format(),
+			RawString("67"),
+		},
+		bodyStructure: &BodyStructure{
+			MIMEType:    "message",
+			MIMESubType: "rfc822",
+			Params:      map[string]string{},
+			Encoding:    "us-ascii",
+			Size:        42,
+			Lines:       67,
+			Envelope: &Envelope{
+				From:    nil,
+				Sender:  nil,
+				ReplyTo: nil,
+				To:      nil,
+				Cc:      nil,
+				Bcc:     nil,
+			},
+			BodyStructure: &BodyStructure{
+				Params: map[string]string{},
+			},
+		},
+	},
+	{
+		fields: []interface{}{
+			"application", "pdf", []interface{}{}, nil, nil, "base64", RawString("4242"),
+			"e0323a9039add2978bf5b49550572c7c",
+			[]interface{}{"attachment", []interface{}{"filename", "document.pdf"}},
+			[]interface{}{"en-US"}, []interface{}{},
+		},
+		bodyStructure: &BodyStructure{
+			MIMEType:          "application",
+			MIMESubType:       "pdf",
+			Params:            map[string]string{},
+			Encoding:          "base64",
+			Size:              4242,
+			Extended:          true,
+			MD5:               "e0323a9039add2978bf5b49550572c7c",
+			Disposition:       "attachment",
+			DispositionParams: map[string]string{"filename": "document.pdf"},
+			Language:          []string{"en-US"},
+			Location:          []string{},
+		},
+	},
+	{
+		fields: []interface{}{
+			[]interface{}{"text", "plain", []interface{}{}, nil, nil, "us-ascii", RawString("87"), RawString("22")},
+			[]interface{}{"text", "html", []interface{}{}, nil, nil, "us-ascii", RawString("106"), RawString("36")},
+			"alternative",
+		},
+		bodyStructure: &BodyStructure{
+			MIMEType:    "multipart",
+			MIMESubType: "alternative",
+			Params:      map[string]string{},
+			Parts: []*BodyStructure{
+				{
+					MIMEType:    "text",
+					MIMESubType: "plain",
+					Params:      map[string]string{},
+					Encoding:    "us-ascii",
+					Size:        87,
+					Lines:       22,
+				},
+				{
+					MIMEType:    "text",
+					MIMESubType: "html",
+					Params:      map[string]string{},
+					Encoding:    "us-ascii",
+					Size:        106,
+					Lines:       36,
+				},
+			},
+		},
+	},
+	{
+		fields: []interface{}{
+			[]interface{}{"text", "plain", []interface{}{}, nil, nil, "us-ascii", RawString("87"), RawString("22")},
+			"alternative", []interface{}{"hello", "world"},
+			[]interface{}{"inline", []interface{}{}},
+			[]interface{}{"en-US"}, []interface{}{},
+		},
+		bodyStructure: &BodyStructure{
+			MIMEType:    "multipart",
+			MIMESubType: "alternative",
+			Params:      map[string]string{"hello": "world"},
+			Parts: []*BodyStructure{
+				{
+					MIMEType:    "text",
+					MIMESubType: "plain",
+					Params:      map[string]string{},
+					Encoding:    "us-ascii",
+					Size:        87,
+					Lines:       22,
+				},
+			},
+			Extended:          true,
+			Disposition:       "inline",
+			DispositionParams: map[string]string{},
+			Language:          []string{"en-US"},
+			Location:          []string{},
+		},
+	},
+}
+
+func TestBodyStructure_Parse(t *testing.T) {
+	for i, test := range bodyStructureTests {
+		bs := &BodyStructure{}
+
+		if err := bs.Parse(test.fields); err != nil {
+			t.Errorf("Cannot parse #%v: %v", i, err)
+		} else if !reflect.DeepEqual(bs, test.bodyStructure) {
+			t.Errorf("Invalid body structure for #%v: got \n%+v\n but expected \n%+v", i, bs, test.bodyStructure)
+		}
+	}
+}
+
+func TestBodyStructure_Parse_uppercase(t *testing.T) {
+	fields := []interface{}{
+		"APPLICATION", "PDF", []interface{}{"NAME", "Document.pdf"}, nil, nil,
+		"BASE64", RawString("4242"), nil,
+		[]interface{}{"ATTACHMENT", []interface{}{"FILENAME", "Document.pdf"}},
+		nil, nil,
+	}
+
+	expected := &BodyStructure{
+		MIMEType:          "application",
+		MIMESubType:       "pdf",
+		Params:            map[string]string{"name": "Document.pdf"},
+		Encoding:          "base64",
+		Size:              4242,
+		Extended:          true,
+		MD5:               "",
+		Disposition:       "attachment",
+		DispositionParams: map[string]string{"filename": "Document.pdf"},
+		Language:          nil,
+		Location:          []string{},
+	}
+
+	bs := &BodyStructure{}
+	if err := bs.Parse(fields); err != nil {
+		t.Errorf("Cannot parse: %v", err)
+	} else if !reflect.DeepEqual(bs, expected) {
+		t.Errorf("Invalid body structure: got \n%+v\n but expected \n%+v", bs, expected)
+	}
+}
+
+func TestBodyStructure_Format(t *testing.T) {
+	for i, test := range bodyStructureTests {
+		fields := test.bodyStructure.Format()
+		got, err := formatFields(fields)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+
+		expected, _ := formatFields(test.fields)
+
+		if got != expected {
+			t.Errorf("Invalid body structure fields for #%v: has \n%v\n but expected \n%v", i, got, expected)
+		}
+	}
+}
+
+func TestBodyStructureFilename(t *testing.T) {
+	tests := []struct {
+		bs       BodyStructure
+		filename string
+	}{
+		{
+			bs: BodyStructure{
+				DispositionParams: map[string]string{"filename": "cat.png"},
+			},
+			filename: "cat.png",
+		},
+		{
+			bs: BodyStructure{
+				Params: map[string]string{"name": "cat.png"},
+			},
+			filename: "cat.png",
+		},
+		{
+			bs:       BodyStructure{},
+			filename: "",
+		},
+		{
+			bs: BodyStructure{
+				DispositionParams: map[string]string{"filename": "=?UTF-8?Q?Opis_przedmiotu_zam=c3=b3wienia_-_za=c5=82=c4=85cznik_nr_1?= =?UTF-8?Q?=2epdf?="},
+			},
+			filename: "Opis przedmiotu zamówienia - załącznik nr 1.pdf",
+		},
+	}
+
+	for i, test := range tests {
+		got, err := test.bs.Filename()
+		if err != nil {
+			t.Errorf("Invalid body structure filename for #%v: error: %v", i, err)
+			continue
+		}
+
+		if got != test.filename {
+			t.Errorf("Invalid body structure filename for #%v: got '%v', want '%v'", i, got, test.filename)
+		}
+	}
+}
+
+func TestBodyStructureWalk(t *testing.T) {
+	textPlain := &BodyStructure{
+		MIMEType:    "text",
+		MIMESubType: "plain",
+	}
+
+	textHTML := &BodyStructure{
+		MIMEType:    "text",
+		MIMESubType: "plain",
+	}
+
+	multipartAlternative := &BodyStructure{
+		MIMEType:    "multipart",
+		MIMESubType: "alternative",
+		Parts:       []*BodyStructure{textPlain, textHTML},
+	}
+
+	imagePNG := &BodyStructure{
+		MIMEType:    "image",
+		MIMESubType: "png",
+	}
+
+	multipartMixed := &BodyStructure{
+		MIMEType:    "multipart",
+		MIMESubType: "mixed",
+		Parts:       []*BodyStructure{multipartAlternative, imagePNG},
+	}
+
+	type testNode struct {
+		path []int
+		part *BodyStructure
+	}
+
+	tests := []struct {
+		bs           *BodyStructure
+		nodes        []testNode
+		walkChildren bool
+	}{
+		{
+			bs: textPlain,
+			nodes: []testNode{
+				{path: []int{1}, part: textPlain},
+			},
+		},
+		{
+			bs: multipartAlternative,
+			nodes: []testNode{
+				{path: nil, part: multipartAlternative},
+				{path: []int{1}, part: textPlain},
+				{path: []int{2}, part: textHTML},
+			},
+			walkChildren: true,
+		},
+		{
+			bs: multipartMixed,
+			nodes: []testNode{
+				{path: nil, part: multipartMixed},
+				{path: []int{1}, part: multipartAlternative},
+				{path: []int{1, 1}, part: textPlain},
+				{path: []int{1, 2}, part: textHTML},
+				{path: []int{2}, part: imagePNG},
+			},
+			walkChildren: true,
+		},
+		{
+			bs: multipartMixed,
+			nodes: []testNode{
+				{path: nil, part: multipartMixed},
+			},
+			walkChildren: false,
+		},
+	}
+
+	for i, test := range tests {
+		j := 0
+		test.bs.Walk(func(path []int, part *BodyStructure) bool {
+			if j >= len(test.nodes) {
+				t.Errorf("Test #%v: invalid node count: got > %v, want %v", i, j, len(test.nodes))
+				return false
+			}
+			n := &test.nodes[j]
+			if !reflect.DeepEqual(path, n.path) {
+				t.Errorf("Test #%v: node #%v: invalid path: got %v, want %v", i, j, path, n.path)
+			}
+			if part != n.part {
+				t.Errorf("Test #%v: node #%v: invalid part: got %v, want %v", i, j, part, n.part)
+			}
+			j++
+			return test.walkChildren
+		})
+		if j != len(test.nodes) {
+			t.Errorf("Test #%v: invalid node count: got %v, want %v", i, j, len(test.nodes))
+		}
+	}
+}

read.go

@@ -0,0 +1,467 @@
+package imap
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"strconv"
+	"strings"
+)
+
+const (
+	sp            = ' '
+	cr            = '\r'
+	lf            = '\n'
+	dquote        = '"'
+	literalStart  = '{'
+	literalEnd    = '}'
+	listStart     = '('
+	listEnd       = ')'
+	respCodeStart = '['
+	respCodeEnd   = ']'
+)
+
+const (
+	crlf    = "\r\n"
+	nilAtom = "NIL"
+)
+
+// TODO: add CTL to atomSpecials
+var (
+	quotedSpecials = string([]rune{dquote, '\\'})
+	respSpecials   = string([]rune{respCodeEnd})
+	atomSpecials   = string([]rune{listStart, listEnd, literalStart, sp, '%', '*'}) + quotedSpecials + respSpecials
+)
+
+type parseError struct {
+	error
+}
+
+func newParseError(text string) error {
+	return &parseError{errors.New(text)}
+}
+
+// IsParseError returns true if the provided error is a parse error produced by
+// Reader.
+func IsParseError(err error) bool {
+	_, ok := err.(*parseError)
+	return ok
+}
+
+// A string reader.
+type StringReader interface {
+	// ReadString reads until the first occurrence of delim in the input,
+	// returning a string containing the data up to and including the delimiter.
+	// See https://golang.org/pkg/bufio/#Reader.ReadString
+	ReadString(delim byte) (line string, err error)
+}
+
+type reader interface {
+	io.Reader
+	io.RuneScanner
+	StringReader
+}
+
+// ParseNumber parses a number.
+func ParseNumber(f interface{}) (uint32, error) {
+	// Useful for tests
+	if n, ok := f.(uint32); ok {
+		return n, nil
+	}
+
+	var s string
+	switch f := f.(type) {
+	case RawString:
+		s = string(f)
+	case string:
+		s = f
+	default:
+		return 0, newParseError("expected a number, got a non-atom")
+	}
+
+	nbr, err := strconv.ParseUint(string(s), 10, 32)
+	if err != nil {
+		return 0, &parseError{err}
+	}
+
+	return uint32(nbr), nil
+}
+
+// ParseString parses a string, which is either a literal, a quoted string or an
+// atom.
+func ParseString(f interface{}) (string, error) {
+	if s, ok := f.(string); ok {
+		return s, nil
+	}
+
+	// Useful for tests
+	if a, ok := f.(RawString); ok {
+		return string(a), nil
+	}
+
+	if l, ok := f.(Literal); ok {
+		b := make([]byte, l.Len())
+		if _, err := io.ReadFull(l, b); err != nil {
+			return "", err
+		}
+		return string(b), nil
+	}
+
+	return "", newParseError("expected a string")
+}
+
+// Convert a field list to a string list.
+func ParseStringList(f interface{}) ([]string, error) {
+	fields, ok := f.([]interface{})
+	if !ok {
+		return nil, newParseError("expected a string list, got a non-list")
+	}
+
+	list := make([]string, len(fields))
+	for i, f := range fields {
+		var err error
+		if list[i], err = ParseString(f); err != nil {
+			return nil, newParseError("cannot parse string in string list: " + err.Error())
+		}
+	}
+	return list, nil
+}
+
+func trimSuffix(str string, suffix rune) string {
+	return str[:len(str)-1]
+}
+
+// An IMAP reader.
+type Reader struct {
+	MaxLiteralSize uint32 // The maximum literal size.
+
+	reader
+
+	continues chan<- bool
+
+	brackets   int
+	inRespCode bool
+}
+
+func (r *Reader) ReadSp() error {
+	char, _, err := r.ReadRune()
+	if err != nil {
+		return err
+	}
+	if char != sp {
+		return newParseError("expected a space")
+	}
+	return nil
+}
+
+func (r *Reader) ReadCrlf() (err error) {
+	var char rune
+
+	if char, _, err = r.ReadRune(); err != nil {
+		return
+	}
+	if char == lf {
+		return
+	}
+	if char != cr {
+		err = newParseError("line doesn't end with a CR")
+		return
+	}
+
+	if char, _, err = r.ReadRune(); err != nil {
+		return
+	}
+	if char != lf {
+		err = newParseError("line doesn't end with a LF")
+	}
+
+	return
+}
+
+func (r *Reader) ReadAtom() (interface{}, error) {
+	r.brackets = 0
+
+	var atom string
+	for {
+		char, _, err := r.ReadRune()
+		if err != nil {
+			return nil, err
+		}
+
+		// TODO: list-wildcards and \
+		if r.brackets == 0 && (char == listStart || char == literalStart || char == dquote) {
+			return nil, newParseError("atom contains forbidden char: " + string(char))
+		}
+		if char == cr || char == lf {
+			break
+		}
+		if r.brackets == 0 && (char == sp || char == listEnd) {
+			break
+		}
+		if char == respCodeEnd {
+			if r.brackets == 0 {
+				if r.inRespCode {
+					break
+				} else {
+					return nil, newParseError("atom contains bad brackets nesting")
+				}
+			}
+			r.brackets--
+		}
+		if char == respCodeStart {
+			r.brackets++
+		}
+
+		atom += string(char)
+	}
+
+	r.UnreadRune()
+
+	if atom == nilAtom {
+		return nil, nil
+	}
+
+	return atom, nil
+}
+
+func (r *Reader) ReadLiteral() (Literal, error) {
+	char, _, err := r.ReadRune()
+	if err != nil {
+		return nil, err
+	} else if char != literalStart {
+		return nil, newParseError("literal string doesn't start with an open brace")
+	}
+
+	lstr, err := r.ReadString(byte(literalEnd))
+	if err != nil {
+		return nil, err
+	}
+	lstr = trimSuffix(lstr, literalEnd)
+
+	nonSync := strings.HasSuffix(lstr, "+")
+	if nonSync {
+		lstr = trimSuffix(lstr, '+')
+	}
+
+	n, err := strconv.ParseUint(lstr, 10, 32)
+	if err != nil {
+		return nil, newParseError("cannot parse literal length: " + err.Error())
+	}
+	if r.MaxLiteralSize > 0 && uint32(n) > r.MaxLiteralSize {
+		return nil, newParseError("literal exceeding maximum size")
+	}
+
+	if err := r.ReadCrlf(); err != nil {
+		return nil, err
+	}
+
+	// Send continuation request if necessary
+	if r.continues != nil && !nonSync {
+		r.continues <- true
+	}
+
+	// Read literal
+	b := make([]byte, n)
+	if _, err := io.ReadFull(r, b); err != nil {
+		return nil, err
+	}
+	return bytes.NewBuffer(b), nil
+}
+
+func (r *Reader) ReadQuotedString() (string, error) {
+	if char, _, err := r.ReadRune(); err != nil {
+		return "", err
+	} else if char != dquote {
+		return "", newParseError("quoted string doesn't start with a double quote")
+	}
+
+	var buf bytes.Buffer
+	var escaped bool
+	for {
+		char, _, err := r.ReadRune()
+		if err != nil {
+			return "", err
+		}
+
+		if char == '\\' && !escaped {
+			escaped = true
+		} else {
+			if char == cr || char == lf {
+				r.UnreadRune()
+				return "", newParseError("CR or LF not allowed in quoted string")
+			}
+			if char == dquote && !escaped {
+				break
+			}
+
+			if !strings.ContainsRune(quotedSpecials, char) && escaped {
+				return "", newParseError("quoted string cannot contain backslash followed by a non-quoted-specials char")
+			}
+
+			buf.WriteRune(char)
+			escaped = false
+		}
+	}
+
+	return buf.String(), nil
+}
+
+func (r *Reader) ReadFields() (fields []interface{}, err error) {
+	var char rune
+	for {
+		if char, _, err = r.ReadRune(); err != nil {
+			return
+		}
+		if err = r.UnreadRune(); err != nil {
+			return
+		}
+
+		var field interface{}
+		ok := true
+		switch char {
+		case literalStart:
+			field, err = r.ReadLiteral()
+		case dquote:
+			field, err = r.ReadQuotedString()
+		case listStart:
+			field, err = r.ReadList()
+		case listEnd:
+			ok = false
+		case cr:
+			return
+		default:
+			field, err = r.ReadAtom()
+		}
+
+		if err != nil {
+			return
+		}
+		if ok {
+			fields = append(fields, field)
+		}
+
+		if char, _, err = r.ReadRune(); err != nil {
+			return
+		}
+		if char == cr || char == lf || char == listEnd || char == respCodeEnd {
+			if char == cr || char == lf {
+				r.UnreadRune()
+			}
+			return
+		}
+		if char == listStart {
+			r.UnreadRune()
+			continue
+		}
+		if char != sp {
+			err = newParseError("fields are not separated by a space")
+			return
+		}
+	}
+}
+
+func (r *Reader) ReadList() (fields []interface{}, err error) {
+	char, _, err := r.ReadRune()
+	if err != nil {
+		return
+	}
+	if char != listStart {
+		err = newParseError("list doesn't start with an open parenthesis")
+		return
+	}
+
+	fields, err = r.ReadFields()
+	if err != nil {
+		return
+	}
+
+	r.UnreadRune()
+	if char, _, err = r.ReadRune(); err != nil {
+		return
+	}
+	if char != listEnd {
+		err = newParseError("list doesn't end with a close parenthesis")
+	}
+	return
+}
+
+func (r *Reader) ReadLine() (fields []interface{}, err error) {
+	fields, err = r.ReadFields()
+	if err != nil {
+		return
+	}
+
+	r.UnreadRune()
+	err = r.ReadCrlf()
+	return
+}
+
+func (r *Reader) ReadRespCode() (code StatusRespCode, fields []interface{}, err error) {
+	char, _, err := r.ReadRune()
+	if err != nil {
+		return
+	}
+	if char != respCodeStart {
+		err = newParseError("response code doesn't start with an open bracket")
+		return
+	}
+
+	r.inRespCode = true
+	fields, err = r.ReadFields()
+	r.inRespCode = false
+	if err != nil {
+		return
+	}
+
+	if len(fields) == 0 {
+		err = newParseError("response code doesn't contain any field")
+		return
+	}
+
+	codeStr, ok := fields[0].(string)
+	if !ok {
+		err = newParseError("response code doesn't start with a string atom")
+		return
+	}
+	if codeStr == "" {
+		err = newParseError("response code is empty")
+		return
+	}
+	code = StatusRespCode(strings.ToUpper(codeStr))
+
+	fields = fields[1:]
+
+	r.UnreadRune()
+	char, _, err = r.ReadRune()
+	if err != nil {
+		return
+	}
+	if char != respCodeEnd {
+		err = newParseError("response code doesn't end with a close bracket")
+	}
+	return
+}
+
+func (r *Reader) ReadInfo() (info string, err error) {
+	info, err = r.ReadString(byte(lf))
+	if err != nil {
+		return
+	}
+	info = strings.TrimSuffix(info, string(lf))
+	info = strings.TrimSuffix(info, string(cr))
+	info = strings.TrimLeft(info, " ")
+
+	return
+}
+
+func NewReader(r reader) *Reader {
+	return &Reader{reader: r}
+}
+
+func NewServerReader(r reader, continues chan<- bool) *Reader {
+	return &Reader{reader: r, continues: continues}
+}
+
+type Parser interface {
+	Parse(fields []interface{}) error
+}

read_test.go

@@ -0,0 +1,536 @@
+package imap_test
+
+import (
+	"bytes"
+	"io"
+	"io/ioutil"
+	"reflect"
+	"testing"
+
+	"github.com/emersion/go-imap"
+)
+
+func TestParseNumber(t *testing.T) {
+	tests := []struct {
+		f   interface{}
+		n   uint32
+		err bool
+	}{
+		{f: "42", n: 42},
+		{f: "0", n: 0},
+		{f: "-1", err: true},
+		{f: "1.2", err: true},
+		{f: nil, err: true},
+		{f: bytes.NewBufferString("cc"), err: true},
+	}
+
+	for _, test := range tests {
+		n, err := imap.ParseNumber(test.f)
+		if err != nil {
+			if !test.err {
+				t.Errorf("Cannot parse number %v", test.f)
+			}
+		} else {
+			if test.err {
+				t.Errorf("Parsed invalid number %v", test.f)
+			} else if n != test.n {
+				t.Errorf("Invalid parsed number: got %v but expected %v", n, test.n)
+			}
+		}
+	}
+}
+
+func TestParseStringList(t *testing.T) {
+	tests := []struct {
+		field interface{}
+		list  []string
+	}{
+		{
+			field: []interface{}{"a", "b", "c", "d"},
+			list:  []string{"a", "b", "c", "d"},
+		},
+		{
+			field: []interface{}{"a"},
+			list:  []string{"a"},
+		},
+		{
+			field: []interface{}{},
+			list:  []string{},
+		},
+		{
+			field: []interface{}{"a", 42, "c", "d"},
+			list:  nil,
+		},
+		{
+			field: []interface{}{"a", nil, "c", "d"},
+			list:  nil,
+		},
+		{
+			field: "Asuka FTW",
+			list:  nil,
+		},
+	}
+
+	for _, test := range tests {
+		list, err := imap.ParseStringList(test.field)
+		if err != nil {
+			if test.list != nil {
+				t.Errorf("Cannot parse string list: %v", err)
+			}
+		} else if !reflect.DeepEqual(list, test.list) {
+			t.Errorf("Invalid parsed string list: got \n%+v\n but expected \n%+v", list, test.list)
+		}
+	}
+}
+
+func newReader(s string) (b *bytes.Buffer, r *imap.Reader) {
+	b = bytes.NewBuffer([]byte(s))
+	r = imap.NewReader(b)
+	return
+}
+
+func TestReader_ReadSp(t *testing.T) {
+	b, r := newReader(" ")
+	if err := r.ReadSp(); err != nil {
+		t.Error(err)
+	}
+	if b.Len() > 0 {
+		t.Error("Buffer is not empty after read")
+	}
+
+	_, r = newReader("")
+	if err := r.ReadSp(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+}
+
+func TestReader_ReadCrlf(t *testing.T) {
+	b, r := newReader("\r\n")
+	if err := r.ReadCrlf(); err != nil {
+		t.Error(err)
+	}
+	if b.Len() > 0 {
+		t.Error("Buffer is not empty after read")
+	}
+
+	_, r = newReader("")
+	if err := r.ReadCrlf(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("\n")
+	if err := r.ReadCrlf(); err != nil {
+		t.Error(err)
+	}
+
+	_, r = newReader("\r")
+	if err := r.ReadCrlf(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("\r42")
+	if err := r.ReadCrlf(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+}
+
+func TestReader_ReadAtom(t *testing.T) {
+	b, r := newReader("NIL\r\n")
+	if atom, err := r.ReadAtom(); err != nil {
+		t.Error(err)
+	} else if atom != nil {
+		t.Error("NIL atom is not nil:", atom)
+	} else {
+		if err := r.ReadCrlf(); err != nil && err != io.EOF {
+			t.Error("Cannot read CRLF after atom:", err)
+		}
+		if b.Len() > 0 {
+			t.Error("Buffer is not empty after read")
+		}
+	}
+
+	b, r = newReader("atom\r\n")
+	if atom, err := r.ReadAtom(); err != nil {
+		t.Error(err)
+	} else if s, ok := atom.(string); !ok || s != "atom" {
+		t.Error("String atom has not the expected value:", atom)
+	} else {
+		if err := r.ReadCrlf(); err != nil && err != io.EOF {
+			t.Error("Cannot read CRLF after atom:", err)
+		}
+		if b.Len() > 0 {
+			t.Error("Buffer is not empty after read")
+		}
+	}
+
+	_, r = newReader("")
+	if _, err := r.ReadAtom(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("(hi there)\r\n")
+	if _, err := r.ReadAtom(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("{42}\r\n")
+	if _, err := r.ReadAtom(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("\"\r\n")
+	if _, err := r.ReadAtom(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("abc]")
+	if _, err := r.ReadAtom(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("[abc]def]ghi")
+	if _, err := r.ReadAtom(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+}
+
+func TestReader_ReadLiteral_NonSync(t *testing.T) {
+	// For synchronizing literal we should send continuation request.
+	b := bytes.NewBuffer([]byte("{7}\r\nabcdefg"))
+	cont := make(chan bool, 5)
+	r := imap.NewServerReader(b, cont)
+	if litr, err := r.ReadLiteral(); err != nil {
+		t.Error(err)
+	} else if litr.Len() != 7 {
+		t.Error("Invalid literal length")
+	} else {
+		if len(cont) != 1 {
+			t.Error("Missing continuation rejqest")
+		}
+		<-cont
+	}
+
+	b = bytes.NewBuffer([]byte("{7+}\r\nabcdefg"))
+	r = imap.NewServerReader(b, cont)
+	if litr, err := r.ReadLiteral(); err != nil {
+		t.Error(err)
+	} else if litr.Len() != 7 {
+		t.Error("Invalid literal length")
+	} else {
+		if len(cont) != 0 {
+			t.Error("Unexpected continuation rejqest")
+		}
+		if contents, err := ioutil.ReadAll(litr); err != nil {
+			t.Error(err)
+		} else if string(contents) != "abcdefg" {
+			t.Error("Literal has not the expected value:", string(contents))
+		} else if b.Len() > 0 {
+			t.Error("Buffer is not empty after read")
+		}
+	}
+}
+
+func TestReader_ReadLiteral(t *testing.T) {
+	b, r := newReader("{7}\r\nabcdefg")
+	if literal, err := r.ReadLiteral(); err != nil {
+		t.Error(err)
+	} else if literal.Len() != 7 {
+		t.Error("Invalid literal length:", literal.Len())
+	} else {
+		if contents, err := ioutil.ReadAll(literal); err != nil {
+			t.Error(err)
+		} else if string(contents) != "abcdefg" {
+			t.Error("Literal has not the expected value:", string(contents))
+		} else if b.Len() > 0 {
+			t.Error("Buffer is not empty after read")
+		}
+	}
+
+	_, r = newReader("")
+	if _, err := r.ReadLiteral(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("[7}\r\nabcdefg")
+	if _, err := r.ReadLiteral(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("{7]\r\nabcdefg")
+	if _, err := r.ReadLiteral(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("{7.4}\r\nabcdefg")
+	if _, err := r.ReadLiteral(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("{7}abcdefg")
+	if _, err := r.ReadLiteral(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("{7}\rabcdefg")
+	if _, err := r.ReadLiteral(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("{7}\nabcdefg")
+	if _, err := r.ReadLiteral(); err != nil {
+		t.Error(err)
+	}
+
+	_, r = newReader("{7}\r\nabcd")
+	if _, err := r.ReadLiteral(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+}
+
+func TestReader_ReadQuotedString(t *testing.T) {
+	b, r := newReader("\"hello gopher\"\r\n")
+	if s, err := r.ReadQuotedString(); err != nil {
+		t.Error(err)
+	} else if s != "hello gopher" {
+		t.Error("Quoted string has not the expected value:", s)
+	} else {
+		if err := r.ReadCrlf(); err != nil && err != io.EOF {
+			t.Error("Cannot read CRLF after quoted string:", err)
+		}
+		if b.Len() > 0 {
+			t.Error("Buffer is not empty after read")
+		}
+	}
+
+	_, r = newReader("\"here's a backslash: \\\\, and here's a double quote: \\\" !\"\r\n")
+	if s, err := r.ReadQuotedString(); err != nil {
+		t.Error(err)
+	} else if s != "here's a backslash: \\, and here's a double quote: \" !" {
+		t.Error("Quoted string has not the expected value:", s)
+	}
+
+	_, r = newReader("")
+	if _, err := r.ReadQuotedString(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("hello gopher\"\r\n")
+	if _, err := r.ReadQuotedString(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("\"hello gopher\r\n")
+	if _, err := r.ReadQuotedString(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("\"hello \\gopher\"\r\n")
+	if _, err := r.ReadQuotedString(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+}
+
+func TestReader_ReadFields(t *testing.T) {
+	b, r := newReader("field1 \"field2\"\r\n")
+	if fields, err := r.ReadFields(); err != nil {
+		t.Error(err)
+	} else if len(fields) != 2 {
+		t.Error("Expected 2 fields, but got", len(fields))
+	} else if s, ok := fields[0].(string); !ok || s != "field1" {
+		t.Error("Field 1 has not the expected value:", fields[0])
+	} else if s, ok := fields[1].(string); !ok || s != "field2" {
+		t.Error("Field 2 has not the expected value:", fields[1])
+	} else {
+		if err := r.ReadCrlf(); err != nil && err != io.EOF {
+			t.Error("Cannot read CRLF after fields:", err)
+		}
+		if b.Len() > 0 {
+			t.Error("Buffer is not empty after read")
+		}
+	}
+
+	_, r = newReader("")
+	if _, err := r.ReadFields(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("fi\"eld1 \"field2\"\r\n")
+	if _, err := r.ReadFields(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("field1 ")
+	if _, err := r.ReadFields(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("field1 (")
+	if _, err := r.ReadFields(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("field1\"field2\"\r\n")
+	if _, err := r.ReadFields(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("\"field1\"\"field2\"\r\n")
+	if _, err := r.ReadFields(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+}
+
+func TestReader_ReadList(t *testing.T) {
+	b, r := newReader("(field1 \"field2\" {6}\r\nfield3 field4)")
+	if fields, err := r.ReadList(); err != nil {
+		t.Error(err)
+	} else if len(fields) != 4 {
+		t.Error("Expected 2 fields, but got", len(fields))
+	} else if s, ok := fields[0].(string); !ok || s != "field1" {
+		t.Error("Field 1 has not the expected value:", fields[0])
+	} else if s, ok := fields[1].(string); !ok || s != "field2" {
+		t.Error("Field 2 has not the expected value:", fields[1])
+	} else if literal, ok := fields[2].(imap.Literal); !ok {
+		t.Error("Field 3 has not the expected value:", fields[2])
+	} else if contents, err := ioutil.ReadAll(literal); err != nil {
+		t.Error(err)
+	} else if string(contents) != "field3" {
+		t.Error("Field 3 has not the expected value:", string(contents))
+	} else if s, ok := fields[3].(string); !ok || s != "field4" {
+		t.Error("Field 4 has not the expected value:", fields[3])
+	} else if b.Len() > 0 {
+		t.Error("Buffer is not empty after read")
+	}
+
+	b, r = newReader("()")
+	if fields, err := r.ReadList(); err != nil {
+		t.Error(err)
+	} else if len(fields) != 0 {
+		t.Error("Expected 0 fields, but got", len(fields))
+	} else if b.Len() > 0 {
+		t.Error("Buffer is not empty after read")
+	}
+
+	_, r = newReader("")
+	if _, err := r.ReadList(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("[field1 field2 field3)")
+	if _, err := r.ReadList(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("(field1 fie\"ld2 field3)")
+	if _, err := r.ReadList(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("(field1 field2 field3\r\n")
+	if _, err := r.ReadList(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+}
+
+func TestReader_ReadLine(t *testing.T) {
+	b, r := newReader("field1 field2\r\n")
+	if fields, err := r.ReadLine(); err != nil {
+		t.Error(err)
+	} else if len(fields) != 2 {
+		t.Error("Expected 2 fields, but got", len(fields))
+	} else if s, ok := fields[0].(string); !ok || s != "field1" {
+		t.Error("Field 1 has not the expected value:", fields[0])
+	} else if s, ok := fields[1].(string); !ok || s != "field2" {
+		t.Error("Field 2 has not the expected value:", fields[1])
+	} else if b.Len() > 0 {
+		t.Error("Buffer is not empty after read")
+	}
+
+	_, r = newReader("")
+	if _, err := r.ReadLine(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("field1 field2\rabc")
+	if _, err := r.ReadLine(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+}
+
+func TestReader_ReadRespCode(t *testing.T) {
+	b, r := newReader("[CAPABILITY NOOP STARTTLS]")
+	if code, fields, err := r.ReadRespCode(); err != nil {
+		t.Error(err)
+	} else if code != imap.CodeCapability {
+		t.Error("Response code has not the expected value:", code)
+	} else if len(fields) != 2 {
+		t.Error("Expected 2 fields, but got", len(fields))
+	} else if s, ok := fields[0].(string); !ok || s != "NOOP" {
+		t.Error("Field 1 has not the expected value:", fields[0])
+	} else if s, ok := fields[1].(string); !ok || s != "STARTTLS" {
+		t.Error("Field 2 has not the expected value:", fields[1])
+	} else if b.Len() > 0 {
+		t.Error("Buffer is not empty after read")
+	}
+
+	_, r = newReader("")
+	if _, _, err := r.ReadRespCode(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("{CAPABILITY NOOP STARTTLS]")
+	if _, _, err := r.ReadRespCode(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("[CAPABILITY NO\"OP STARTTLS]")
+	if _, _, err := r.ReadRespCode(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("[]")
+	if _, _, err := r.ReadRespCode(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("[{3}\r\nabc]")
+	if _, _, err := r.ReadRespCode(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("[CAPABILITY NOOP STARTTLS\r\n")
+	if _, _, err := r.ReadRespCode(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+}
+
+func TestReader_ReadInfo(t *testing.T) {
+	b, r := newReader("I love potatoes.\r\n")
+	if info, err := r.ReadInfo(); err != nil {
+		t.Error(err)
+	} else if info != "I love potatoes." {
+		t.Error("Info has not the expected value:", info)
+	} else if b.Len() > 0 {
+		t.Error("Buffer is not empty after read")
+	}
+
+	_, r = newReader("I love potatoes.")
+	if _, err := r.ReadInfo(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("I love potatoes.\r")
+	if _, err := r.ReadInfo(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+
+	_, r = newReader("I love potatoes.\n")
+	if _, err := r.ReadInfo(); err != nil {
+		t.Error(err)
+	}
+
+	_, r = newReader("I love potatoes.\rabc")
+	if _, err := r.ReadInfo(); err == nil {
+		t.Error("Invalid read didn't fail")
+	}
+}

response.go

@@ -1,81 +1,181 @@
 package imap
 
 import (
-	"fmt"
 	"strings"
 )
 
-// StatusResponseType is a generic status response type.
-type StatusResponseType string
-
-const (
-	StatusResponseTypeOK      StatusResponseType = "OK"
-	StatusResponseTypeNo      StatusResponseType = "NO"
-	StatusResponseTypeBad     StatusResponseType = "BAD"
-	StatusResponseTypePreAuth StatusResponseType = "PREAUTH"
-	StatusResponseTypeBye     StatusResponseType = "BYE"
-)
-
-// ResponseCode is a response code.
-type ResponseCode string
-
-const (
-	ResponseCodeAlert                ResponseCode = "ALERT"
-	ResponseCodeAlreadyExists        ResponseCode = "ALREADYEXISTS"
-	ResponseCodeAuthenticationFailed ResponseCode = "AUTHENTICATIONFAILED"
-	ResponseCodeAuthorizationFailed  ResponseCode = "AUTHORIZATIONFAILED"
-	ResponseCodeBadCharset           ResponseCode = "BADCHARSET"
-	ResponseCodeCannot               ResponseCode = "CANNOT"
-	ResponseCodeClientBug            ResponseCode = "CLIENTBUG"
-	ResponseCodeContactAdmin         ResponseCode = "CONTACTADMIN"
-	ResponseCodeCorruption           ResponseCode = "CORRUPTION"
-	ResponseCodeExpired              ResponseCode = "EXPIRED"
-	ResponseCodeHasChildren          ResponseCode = "HASCHILDREN"
-	ResponseCodeInUse                ResponseCode = "INUSE"
-	ResponseCodeLimit                ResponseCode = "LIMIT"
-	ResponseCodeNonExistent          ResponseCode = "NONEXISTENT"
-	ResponseCodeNoPerm               ResponseCode = "NOPERM"
-	ResponseCodeOverQuota            ResponseCode = "OVERQUOTA"
-	ResponseCodeParse                ResponseCode = "PARSE"
-	ResponseCodePrivacyRequired      ResponseCode = "PRIVACYREQUIRED"
-	ResponseCodeServerBug            ResponseCode = "SERVERBUG"
-	ResponseCodeTryCreate            ResponseCode = "TRYCREATE"
-	ResponseCodeUnavailable          ResponseCode = "UNAVAILABLE"
-	ResponseCodeUnknownCTE           ResponseCode = "UNKNOWN-CTE"
-
-	// METADATA
-	ResponseCodeTooMany   ResponseCode = "TOOMANY"
-	ResponseCodeNoPrivate ResponseCode = "NOPRIVATE"
-
-	// APPENDLIMIT
-	ResponseCodeTooBig ResponseCode = "TOOBIG"
-)
-
-// StatusResponse is a generic status response.
-//
-// See RFC 9051 section 7.1.
-type StatusResponse struct {
-	Type StatusResponseType
-	Code ResponseCode
-	Text string
+// Resp is an IMAP response. It is either a *DataResp, a
+// *ContinuationReq or a *StatusResp.
+type Resp interface {
+	resp()
 }
 
-// Error is an IMAP error caused by a status response.
-type Error StatusResponse
-
-var _ error = (*Error)(nil)
-
-// Error implements the error interface.
-func (err *Error) Error() string {
-	var sb strings.Builder
-	fmt.Fprintf(&sb, "imap: %v", err.Type)
-	if err.Code != "" {
-		fmt.Fprintf(&sb, " [%v]", err.Code)
+// ReadResp reads a single response from a Reader.
+func ReadResp(r *Reader) (Resp, error) {
+	atom, err := r.ReadAtom()
+	if err != nil {
+		return nil, err
 	}
-	text := err.Text
-	if text == "" {
-		text = "<unknown>"
+	tag, ok := atom.(string)
+	if !ok {
+		return nil, newParseError("response tag is not an atom")
 	}
-	fmt.Fprintf(&sb, " %v", text)
-	return sb.String()
+
+	if tag == "+" {
+		if err := r.ReadSp(); err != nil {
+			r.UnreadRune()
+		}
+
+		resp := &ContinuationReq{}
+		resp.Info, err = r.ReadInfo()
+		if err != nil {
+			return nil, err
+		}
+
+		return resp, nil
+	}
+
+	if err := r.ReadSp(); err != nil {
+		return nil, err
+	}
+
+	// Can be either data or status
+	// Try to parse a status
+	var fields []interface{}
+	if atom, err := r.ReadAtom(); err == nil {
+		fields = append(fields, atom)
+
+		if err := r.ReadSp(); err == nil {
+			if name, ok := atom.(string); ok {
+				status := StatusRespType(name)
+				switch status {
+				case StatusRespOk, StatusRespNo, StatusRespBad, StatusRespPreauth, StatusRespBye:
+					resp := &StatusResp{
+						Tag:  tag,
+						Type: status,
+					}
+
+					char, _, err := r.ReadRune()
+					if err != nil {
+						return nil, err
+					}
+					r.UnreadRune()
+
+					if char == '[' {
+						// Contains code & arguments
+						resp.Code, resp.Arguments, err = r.ReadRespCode()
+						if err != nil {
+							return nil, err
+						}
+					}
+
+					resp.Info, err = r.ReadInfo()
+					if err != nil {
+						return nil, err
+					}
+
+					return resp, nil
+				}
+			}
+		} else {
+			r.UnreadRune()
+		}
+	} else {
+		r.UnreadRune()
+	}
+
+	// Not a status so it's data
+	resp := &DataResp{Tag: tag}
+
+	var remaining []interface{}
+	remaining, err = r.ReadLine()
+	if err != nil {
+		return nil, err
+	}
+
+	resp.Fields = append(fields, remaining...)
+	return resp, nil
+}
+
+// DataResp is an IMAP response containing data.
+type DataResp struct {
+	// The response tag. Can be either "" for untagged responses, "+" for continuation
+	// requests or a previous command's tag.
+	Tag string
+	// The parsed response fields.
+	Fields []interface{}
+}
+
+// NewUntaggedResp creates a new untagged response.
+func NewUntaggedResp(fields []interface{}) *DataResp {
+	return &DataResp{
+		Tag:    "*",
+		Fields: fields,
+	}
+}
+
+func (r *DataResp) resp() {}
+
+func (r *DataResp) WriteTo(w *Writer) error {
+	tag := RawString(r.Tag)
+	if tag == "" {
+		tag = RawString("*")
+	}
+
+	fields := []interface{}{RawString(tag)}
+	fields = append(fields, r.Fields...)
+	return w.writeLine(fields...)
+}
+
+// ContinuationReq is a continuation request response.
+type ContinuationReq struct {
+	// The info message sent with the continuation request.
+	Info string
+}
+
+func (r *ContinuationReq) resp() {}
+
+func (r *ContinuationReq) WriteTo(w *Writer) error {
+	if err := w.writeString("+"); err != nil {
+		return err
+	}
+
+	if r.Info != "" {
+		if err := w.writeString(string(sp) + r.Info); err != nil {
+			return err
+		}
+	}
+
+	return w.writeCrlf()
+}
+
+// ParseNamedResp attempts to parse a named data response.
+func ParseNamedResp(resp Resp) (name string, fields []interface{}, ok bool) {
+	data, ok := resp.(*DataResp)
+	if !ok || len(data.Fields) == 0 {
+		return
+	}
+
+	// Some responses (namely EXISTS and RECENT) are formatted like so:
+	//   [num] [name] [...]
+	// Which is fucking stupid. But we handle that here by checking if the
+	// response name is a number and then rearranging it.
+	if len(data.Fields) > 1 {
+		name, ok := data.Fields[1].(string)
+		if ok {
+			if _, err := ParseNumber(data.Fields[0]); err == nil {
+				fields := []interface{}{data.Fields[0]}
+				fields = append(fields, data.Fields[2:]...)
+				return strings.ToUpper(name), fields, true
+			}
+		}
+	}
+
+	// IMAP commands are formatted like this:
+	//   [name] [...]
+	name, ok = data.Fields[0].(string)
+	if !ok {
+		return
+	}
+	return strings.ToUpper(name), data.Fields[1:], true
 }

response_test.go

@@ -0,0 +1,252 @@
+package imap_test
+
+import (
+	"bytes"
+	"reflect"
+	"testing"
+
+	"github.com/emersion/go-imap"
+)
+
+func TestResp_WriteTo(t *testing.T) {
+	var b bytes.Buffer
+	w := imap.NewWriter(&b)
+
+	resp := imap.NewUntaggedResp([]interface{}{imap.RawString("76"), imap.RawString("FETCH"), []interface{}{imap.RawString("UID"), 783}})
+	if err := resp.WriteTo(w); err != nil {
+		t.Fatal(err)
+	}
+
+	if b.String() != "* 76 FETCH (UID 783)\r\n" {
+		t.Error("Invalid response:", b.String())
+	}
+}
+
+func TestContinuationReq_WriteTo(t *testing.T) {
+	var b bytes.Buffer
+	w := imap.NewWriter(&b)
+
+	resp := &imap.ContinuationReq{}
+
+	if err := resp.WriteTo(w); err != nil {
+		t.Fatal(err)
+	}
+
+	if b.String() != "+\r\n" {
+		t.Error("Invalid continuation:", b.String())
+	}
+}
+
+func TestContinuationReq_WriteTo_WithInfo(t *testing.T) {
+	var b bytes.Buffer
+	w := imap.NewWriter(&b)
+
+	resp := &imap.ContinuationReq{Info: "send literal"}
+
+	if err := resp.WriteTo(w); err != nil {
+		t.Fatal(err)
+	}
+
+	if b.String() != "+ send literal\r\n" {
+		t.Error("Invalid continuation:", b.String())
+	}
+}
+
+func TestReadResp_ContinuationReq(t *testing.T) {
+	b := bytes.NewBufferString("+ send literal\r\n")
+	r := imap.NewReader(b)
+
+	resp, err := imap.ReadResp(r)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cont, ok := resp.(*imap.ContinuationReq)
+	if !ok {
+		t.Fatal("Response is not a continuation request")
+	}
+
+	if cont.Info != "send literal" {
+		t.Error("Invalid info:", cont.Info)
+	}
+}
+
+func TestReadResp_ContinuationReq_NoInfo(t *testing.T) {
+	b := bytes.NewBufferString("+\r\n")
+	r := imap.NewReader(b)
+
+	resp, err := imap.ReadResp(r)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cont, ok := resp.(*imap.ContinuationReq)
+	if !ok {
+		t.Fatal("Response is not a continuation request")
+	}
+
+	if cont.Info != "" {
+		t.Error("Invalid info:", cont.Info)
+	}
+}
+
+func TestReadResp_Resp(t *testing.T) {
+	b := bytes.NewBufferString("* 1 EXISTS\r\n")
+	r := imap.NewReader(b)
+
+	resp, err := imap.ReadResp(r)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	data, ok := resp.(*imap.DataResp)
+	if !ok {
+		t.Fatal("Invalid response type")
+	}
+
+	if data.Tag != "*" {
+		t.Error("Invalid tag:", data.Tag)
+	}
+	if len(data.Fields) != 2 {
+		t.Error("Invalid fields:", data.Fields)
+	}
+}
+
+func TestReadResp_Resp_NoArgs(t *testing.T) {
+	b := bytes.NewBufferString("* SEARCH\r\n")
+	r := imap.NewReader(b)
+
+	resp, err := imap.ReadResp(r)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	data, ok := resp.(*imap.DataResp)
+	if !ok {
+		t.Fatal("Invalid response type")
+	}
+
+	if data.Tag != "*" {
+		t.Error("Invalid tag:", data.Tag)
+	}
+	if len(data.Fields) != 1 || data.Fields[0] != "SEARCH" {
+		t.Error("Invalid fields:", data.Fields)
+	}
+}
+
+func TestReadResp_StatusResp(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected *imap.StatusResp
+	}{
+		{
+			input: "* OK IMAP4rev1 Service Ready\r\n",
+			expected: &imap.StatusResp{
+				Tag:  "*",
+				Type: imap.StatusRespOk,
+				Info: "IMAP4rev1 Service Ready",
+			},
+		},
+		{
+			input: "* PREAUTH Welcome Pauline!\r\n",
+			expected: &imap.StatusResp{
+				Tag:  "*",
+				Type: imap.StatusRespPreauth,
+				Info: "Welcome Pauline!",
+			},
+		},
+		{
+			input: "a001 OK NOOP completed\r\n",
+			expected: &imap.StatusResp{
+				Tag:  "a001",
+				Type: imap.StatusRespOk,
+				Info: "NOOP completed",
+			},
+		},
+		{
+			input: "a001 OK [READ-ONLY] SELECT completed\r\n",
+			expected: &imap.StatusResp{
+				Tag:  "a001",
+				Type: imap.StatusRespOk,
+				Code: "READ-ONLY",
+				Info: "SELECT completed",
+			},
+		},
+		{
+			input: "a001 OK [CAPABILITY IMAP4rev1 UIDPLUS] LOGIN completed\r\n",
+			expected: &imap.StatusResp{
+				Tag:       "a001",
+				Type:      imap.StatusRespOk,
+				Code:      "CAPABILITY",
+				Arguments: []interface{}{"IMAP4rev1", "UIDPLUS"},
+				Info:      "LOGIN completed",
+			},
+		},
+	}
+
+	for _, test := range tests {
+		b := bytes.NewBufferString(test.input)
+		r := imap.NewReader(b)
+
+		resp, err := imap.ReadResp(r)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		status, ok := resp.(*imap.StatusResp)
+		if !ok {
+			t.Fatal("Response is not a status:", resp)
+		}
+
+		if status.Tag != test.expected.Tag {
+			t.Errorf("Invalid tag: expected %v but got %v", status.Tag, test.expected.Tag)
+		}
+		if status.Type != test.expected.Type {
+			t.Errorf("Invalid type: expected %v but got %v", status.Type, test.expected.Type)
+		}
+		if status.Code != test.expected.Code {
+			t.Errorf("Invalid code: expected %v but got %v", status.Code, test.expected.Code)
+		}
+		if len(status.Arguments) != len(test.expected.Arguments) {
+			t.Errorf("Invalid arguments: expected %v but got %v", status.Arguments, test.expected.Arguments)
+		}
+		if status.Info != test.expected.Info {
+			t.Errorf("Invalid info: expected %v but got %v", status.Info, test.expected.Info)
+		}
+	}
+}
+
+func TestParseNamedResp(t *testing.T) {
+	tests := []struct {
+		resp   *imap.DataResp
+		name   string
+		fields []interface{}
+	}{
+		{
+			resp:   &imap.DataResp{Fields: []interface{}{"CAPABILITY", "IMAP4rev1"}},
+			name:   "CAPABILITY",
+			fields: []interface{}{"IMAP4rev1"},
+		},
+		{
+			resp:   &imap.DataResp{Fields: []interface{}{"42", "EXISTS"}},
+			name:   "EXISTS",
+			fields: []interface{}{"42"},
+		},
+		{
+			resp:   &imap.DataResp{Fields: []interface{}{"42", "FETCH", "blah"}},
+			name:   "FETCH",
+			fields: []interface{}{"42", "blah"},
+		},
+	}
+
+	for _, test := range tests {
+		name, fields, ok := imap.ParseNamedResp(test.resp)
+		if !ok {
+			t.Errorf("ParseNamedResp(%v)[2] = false, want true", test.resp)
+		} else if name != test.name {
+			t.Errorf("ParseNamedResp(%v)[0] = %v, want %v", test.resp, name, test.name)
+		} else if !reflect.DeepEqual(fields, test.fields) {
+			t.Errorf("ParseNamedResp(%v)[1] = %v, want %v", test.resp, fields, test.fields)
+		}
+	}
+}

responses/authenticate.go

@@ -0,0 +1,61 @@
+package responses
+
+import (
+	"encoding/base64"
+
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-sasl"
+)
+
+// An AUTHENTICATE response.
+type Authenticate struct {
+	Mechanism       sasl.Client
+	InitialResponse []byte
+	RepliesCh       chan []byte
+}
+
+// Implements
+func (r *Authenticate) Replies() <-chan []byte {
+	return r.RepliesCh
+}
+
+func (r *Authenticate) writeLine(l string) error {
+	r.RepliesCh <- []byte(l + "\r\n")
+	return nil
+}
+
+func (r *Authenticate) cancel() error {
+	return r.writeLine("*")
+}
+
+func (r *Authenticate) Handle(resp imap.Resp) error {
+	cont, ok := resp.(*imap.ContinuationReq)
+	if !ok {
+		return ErrUnhandled
+	}
+
+	// Empty challenge, send initial response as stated in RFC 2222 section 5.1
+	if cont.Info == "" && r.InitialResponse != nil {
+		encoded := base64.StdEncoding.EncodeToString(r.InitialResponse)
+		if err := r.writeLine(encoded); err != nil {
+			return err
+		}
+		r.InitialResponse = nil
+		return nil
+	}
+
+	challenge, err := base64.StdEncoding.DecodeString(cont.Info)
+	if err != nil {
+		r.cancel()
+		return err
+	}
+
+	reply, err := r.Mechanism.Next(challenge)
+	if err != nil {
+		r.cancel()
+		return err
+	}
+
+	encoded := base64.StdEncoding.EncodeToString(reply)
+	return r.writeLine(encoded)
+}

responses/capability.go

@@ -0,0 +1,20 @@
+package responses
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// A CAPABILITY response.
+// See RFC 3501 section 7.2.1
+type Capability struct {
+	Caps []string
+}
+
+func (r *Capability) WriteTo(w *imap.Writer) error {
+	fields := []interface{}{imap.RawString("CAPABILITY")}
+	for _, cap := range r.Caps {
+		fields = append(fields, imap.RawString(cap))
+	}
+
+	return imap.NewUntaggedResp(fields).WriteTo(w)
+}

responses/enabled.go

@@ -0,0 +1,33 @@
+package responses
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// An ENABLED response, defined in RFC 5161 section 3.2.
+type Enabled struct {
+	Caps []string
+}
+
+func (r *Enabled) Handle(resp imap.Resp) error {
+	name, fields, ok := imap.ParseNamedResp(resp)
+	if !ok || name != "ENABLED" {
+		return ErrUnhandled
+	}
+
+	if caps, err := imap.ParseStringList(fields); err != nil {
+		return err
+	} else {
+		r.Caps = append(r.Caps, caps...)
+	}
+
+	return nil
+}
+
+func (r *Enabled) WriteTo(w *imap.Writer) error {
+	fields := []interface{}{imap.RawString("ENABLED")}
+	for _, cap := range r.Caps {
+		fields = append(fields, imap.RawString(cap))
+	}
+	return imap.NewUntaggedResp(fields).WriteTo(w)
+}

responses/expunge.go

@@ -0,0 +1,43 @@
+package responses
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+const expungeName = "EXPUNGE"
+
+// An EXPUNGE response.
+// See RFC 3501 section 7.4.1
+type Expunge struct {
+	SeqNums chan uint32
+}
+
+func (r *Expunge) Handle(resp imap.Resp) error {
+	name, fields, ok := imap.ParseNamedResp(resp)
+	if !ok || name != expungeName {
+		return ErrUnhandled
+	}
+
+	if len(fields) == 0 {
+		return errNotEnoughFields
+	}
+
+	seqNum, err := imap.ParseNumber(fields[0])
+	if err != nil {
+		return err
+	}
+
+	r.SeqNums <- seqNum
+	return nil
+}
+
+func (r *Expunge) WriteTo(w *imap.Writer) error {
+	for seqNum := range r.SeqNums {
+		resp := imap.NewUntaggedResp([]interface{}{seqNum, imap.RawString(expungeName)})
+		if err := resp.WriteTo(w); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}

responses/fetch.go

@@ -0,0 +1,70 @@
+package responses
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+const fetchName = "FETCH"
+
+// A FETCH response.
+// See RFC 3501 section 7.4.2
+type Fetch struct {
+	Messages chan *imap.Message
+	SeqSet   *imap.SeqSet
+	Uid      bool
+}
+
+func (r *Fetch) Handle(resp imap.Resp) error {
+	name, fields, ok := imap.ParseNamedResp(resp)
+	if !ok || name != fetchName {
+		return ErrUnhandled
+	} else if len(fields) < 1 {
+		return errNotEnoughFields
+	}
+
+	seqNum, err := imap.ParseNumber(fields[0])
+	if err != nil {
+		return err
+	}
+
+	msgFields, _ := fields[1].([]interface{})
+	msg := &imap.Message{SeqNum: seqNum}
+	if err := msg.Parse(msgFields); err != nil {
+		return err
+	}
+
+	if r.Uid && msg.Uid == 0 {
+		// we requested UIDs and got a message without one --> unilateral update --> ignore
+		return ErrUnhandled
+	}
+
+	var num uint32
+	if r.Uid {
+		num = msg.Uid
+	} else {
+		num = seqNum
+	}
+
+	// Check whether we obtained a result we requested with our SeqSet
+	// If the result is not contained in our SeqSet we have to handle an additional special case:
+	// In case we requested UIDs with a dynamic sequence (i.e. * or n:*) and the maximum UID of the mailbox
+	// is less then our n, the server will supply us with the max UID (cf. RFC 3501 §6.4.8 and §9 `seq-range`).
+	// Thus, such a result is correct and has to be returned by us.
+	if !r.SeqSet.Contains(num) && (!r.Uid || !r.SeqSet.Dynamic()) {
+		return ErrUnhandled
+	}
+
+	r.Messages <- msg
+	return nil
+}
+
+func (r *Fetch) WriteTo(w *imap.Writer) error {
+	var err error
+	for msg := range r.Messages {
+		resp := imap.NewUntaggedResp([]interface{}{msg.SeqNum, imap.RawString(fetchName), msg.Format()})
+		if err == nil {
+			err = resp.WriteTo(w)
+		}
+	}
+	return err
+}

responses/idle.go

@@ -0,0 +1,38 @@
+package responses
+
+import (
+	"github.com/emersion/go-imap"
+)
+
+// An IDLE response.
+type Idle struct {
+	RepliesCh chan []byte
+	Stop      <-chan struct{}
+
+	gotContinuationReq bool
+}
+
+func (r *Idle) Replies() <-chan []byte {
+	return r.RepliesCh
+}
+
+func (r *Idle) stop() {
+	r.RepliesCh <- []byte("DONE\r\n")
+}
+
+func (r *Idle) Handle(resp imap.Resp) error {
+	// Wait for a continuation request
+	if _, ok := resp.(*imap.ContinuationReq); ok && !r.gotContinuationReq {
+		r.gotContinuationReq = true
+
+		// We got a continuation request, wait for r.Stop to be closed
+		go func() {
+			<-r.Stop
+			r.stop()
+		}()
+
+		return nil
+	}
+
+	return ErrUnhandled
+}