Merge support for IDLE extension

Author: emersion

client/cmd_auth.go

@@ -276,3 +276,105 @@ func (c *Client) Enable(caps []string) ([]string, error) {
 		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/example_test.go

@@ -281,3 +281,43 @@ func ExampleClient_Search() {
 
 	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
+		}
+	}
+}

server/cmd_auth.go

@@ -1,7 +1,9 @@
 package server
 
 import (
+	"bufio"
 	"errors"
+	"strings"
 
 	"github.com/emersion/go-imap"
 	"github.com/emersion/go-imap/backend"
@@ -297,3 +299,26 @@ func (cmd *Unselect) Handle(conn Conn) error {
 	ctx.MailboxReadOnly = false
 	return nil
 }
+
+type Idle struct {
+	commands.Idle
+}
+
+func (cmd *Idle) Handle(conn Conn) error {
+	cont := &imap.ContinuationReq{Info: "idling"}
+	if err := conn.WriteResp(cont); err != nil {
+		return err
+	}
+
+	// Wait for DONE
+	scanner := bufio.NewScanner(conn)
+	scanner.Scan()
+	if err := scanner.Err(); err != nil {
+		return err
+	}
+
+	if strings.ToUpper(scanner.Text()) != "DONE" {
+		return errors.New("Expected DONE")
+	}
+	return nil
+}

server/server.go

@@ -177,6 +177,7 @@ func New(bkd backend.Backend) *Server {
 		"STATUS":   func() Handler { return &Status{} },
 		"APPEND":   func() Handler { return &Append{} },
 		"UNSELECT": func() Handler { return &Unselect{} },
+		"IDLE":     func() Handler { return &Idle{} },
 
 		"CHECK":   func() Handler { return &Check{} },
 		"CLOSE":   func() Handler { return &Close{} },