imap: manage idle mode with an idler

Untangle the idle functionality from the message handling routine. Wait
for the idle mode to properly exit every time to ensure a consistent
imap state. Timeout when hanging in idle mode and inform the ui.

Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

3 files changed, 181 insertions, 24 deletions

diff --git a/worker/imap/configure.go b/worker/imap/configure.go
index ac1d606..0bccbae 100644
--- a/worker/imap/configure.go
+++ b/worker/imap/configure.go
@@ -95,5 +95,7 @@ func (w *IMAPWorker) handleConfigure(msg *types.Configure) error {
 		}
 	}
 
+	w.idler = newIdler(w.config, w.worker)
+
 	return nil
 }
diff --git a/worker/imap/idler.go b/worker/imap/idler.go
new file mode 100644
index 0000000..e9aecfd
--- /dev/null
+++ b/worker/imap/idler.go
@@ -0,0 +1,149 @@
+package imap
+
+import (
+	"fmt"
+	"sync"
+	"time"
+
+	"git.sr.ht/~rjarry/aerc/logging"
+	"git.sr.ht/~rjarry/aerc/worker/types"
+	"github.com/emersion/go-imap"
+	"github.com/emersion/go-imap/client"
+)
+
+var (
+	errIdleTimeout   = fmt.Errorf("idle timeout")
+	errIdleModeHangs = fmt.Errorf("idle mode hangs; waiting to reconnect")
+)
+
+// idler manages the idle mode of the imap server. Enter idle mode if there's
+// no other task and leave idle mode when a new task arrives. Idle mode is only
+// used when the client is ready and connected. After a connection loss, make
+// sure that idling returns gracefully and the worker remains responsive.
+type idler struct {
+	sync.Mutex
+	config  imapConfig
+	client  *imapClient
+	worker  *types.Worker
+	stop    chan struct{}
+	done    chan error
+	waiting bool
+	idleing bool
+}
+
+func newIdler(cfg imapConfig, w *types.Worker) *idler {
+	return &idler{config: cfg, worker: w, done: make(chan error)}
+}
+
+func (i *idler) SetClient(c *imapClient) {
+	i.Lock()
+	i.client = c
+	i.Unlock()
+}
+
+func (i *idler) setWaiting(wait bool) {
+	i.Lock()
+	i.waiting = wait
+	i.Unlock()
+}
+
+func (i *idler) isWaiting() bool {
+	i.Lock()
+	defer i.Unlock()
+	return i.waiting
+}
+
+func (i *idler) isReady() bool {
+	i.Lock()
+	defer i.Unlock()
+	return (!i.waiting && i.client != nil &&
+		i.client.State() == imap.SelectedState)
+}
+
+func (i *idler) Start() {
+	if i.isReady() {
+		i.stop = make(chan struct{})
+		go func() {
+			defer logging.PanicHandler()
+			i.idleing = true
+			i.log("=>(idle)")
+			now := time.Now()
+			err := i.client.Idle(i.stop,
+				&client.IdleOptions{
+					LogoutTimeout: 0,
+					PollInterval:  0,
+				})
+			i.idleing = false
+			i.done <- err
+			i.log("elapsed ideling time:", time.Since(now))
+		}()
+	} else if i.isWaiting() {
+		i.log("not started: wait for idle to exit")
+	} else {
+		i.log("not started: client not ready")
+	}
+}
+
+func (i *idler) Stop() error {
+	var reterr error
+	if i.isReady() {
+		close(i.stop)
+		select {
+		case err := <-i.done:
+			if err == nil {
+				i.log("<=(idle)")
+			} else {
+				i.log("<=(idle) with err:", err)
+			}
+			reterr = nil
+		case <-time.After(i.config.idle_timeout):
+			i.log("idle err (timeout); waiting in background")
+
+			i.log("disconnect done->")
+			i.worker.PostMessage(&types.Done{
+				Message: types.RespondTo(&types.Disconnect{}),
+			}, nil)
+
+			i.waitOnIdle()
+
+			reterr = errIdleTimeout
+		}
+	} else if i.isWaiting() {
+		i.log("not stopped: still idleing/hanging")
+		reterr = errIdleModeHangs
+	} else {
+		i.log("not stopped: client not ready")
+		reterr = nil
+	}
+	return reterr
+}
+
+func (i *idler) waitOnIdle() {
+	i.setWaiting(true)
+	i.log("wait for idle in background")
+	go func() {
+		defer logging.PanicHandler()
+		select {
+		case err := <-i.done:
+			if err == nil {
+				i.log("<=(idle) waited")
+				i.log("connect done->")
+				i.worker.PostMessage(&types.Done{
+					Message: types.RespondTo(&types.Connect{}),
+				}, nil)
+			} else {
+				i.log("<=(idle) waited; with err:", err)
+			}
+			i.setWaiting(false)
+			i.stop = make(chan struct{})
+			i.log("restart")
+			i.Start()
+			return
+		}
+	}()
+}
+
+func (i *idler) log(args ...interface{}) {
+	header := fmt.Sprintf("idler (%p) [idle:%t,wait:%t]", i, i.idleing, i.waiting)
+	i.worker.Logger.Println(append([]interface{}{header}, args...)...)
+}
diff --git a/worker/imap/worker.go b/worker/imap/worker.go
index ad08333..d0f8482 100644
--- a/worker/imap/worker.go
+++ b/worker/imap/worker.go
@@ -14,7 +14,6 @@ import (
 	"github.com/pkg/errors"
 
 	"git.sr.ht/~rjarry/aerc/lib"
-	"git.sr.ht/~rjarry/aerc/logging"
 	"git.sr.ht/~rjarry/aerc/models"
 	"git.sr.ht/~rjarry/aerc/worker/handlers"
 	"git.sr.ht/~rjarry/aerc/worker/types"
@@ -56,44 +55,43 @@ type IMAPWorker struct {
 	config imapConfig
 
 	client   *imapClient
-	idleStop chan struct{}
-	idleDone chan error
 	selected *imap.MailboxStatus
 	updates  chan client.Update
 	worker   *types.Worker
 	// Map of sequence numbers to UIDs, index 0 is seq number 1
-	seqMap        []uint32
+	seqMap []uint32
+
 	done          chan struct{}
 	autoReconnect bool
 	retries       int
+
+	idler *idler
 }
 
 func NewIMAPWorker(worker *types.Worker) (types.Backend, error) {
 	return &IMAPWorker{
-		idleDone: make(chan error),
 		updates:  make(chan client.Update, 50),
 		worker:   worker,
 		selected: &imap.MailboxStatus{},
+		idler:    newIdler(imapConfig{}, worker),
 	}, nil
 }
 
+func (w *IMAPWorker) newClient(c *client.Client) {
+	c.Updates = w.updates
+	w.client = &imapClient{c, sortthread.NewThreadClient(c), sortthread.NewSortClient(c)}
+	w.idler.SetClient(w.client)
+}
+
 func (w *IMAPWorker) handleMessage(msg types.WorkerMessage) error {
-	if w.client != nil && w.client.State() == imap.SelectedState {
-		close(w.idleStop)
-		if err := <-w.idleDone; err != nil {
-			w.worker.PostMessage(&types.Error{Error: err}, nil)
-		}
-	}
 	defer func() {
-		if w.client != nil && w.client.State() == imap.SelectedState {
-			w.idleStop = make(chan struct{})
-			go func() {
-				defer logging.PanicHandler()
-
-				w.idleDone <- w.client.Idle(w.idleStop, &client.IdleOptions{LogoutTimeout: 0, PollInterval: 0})
-			}()
-		}
+		w.idler.Start()
 	}()
+	if err := w.idler.Stop(); err != nil {
+		return err
+	}
+
+	var reterr error // will be returned at the end, needed to support idle
 
 	checkConn := func(wait time.Duration) {
 		time.Sleep(wait)
@@ -101,7 +99,10 @@ func (w *IMAPWorker) handleMessage(msg types.WorkerMessage) error {
 		w.startConnectionObserver()
 	}
 
-	var reterr error // will be returned at the end, needed to support idle
+	// set connection timeout for calls to imap server
+	if w.client != nil {
+		w.client.Timeout = w.config.connection_timeout
+	}
 
 	switch msg := msg.(type) {
 	case *types.Unsupported:
@@ -128,8 +129,7 @@ func (w *IMAPWorker) handleMessage(msg types.WorkerMessage) error {
 
 		w.stopConnectionObserver()
 
-		c.Updates = w.updates
-		w.client = &imapClient{c, sortthread.NewThreadClient(c), sortthread.NewSortClient(c)}
+		w.newClient(c)
 
 		w.startConnectionObserver()
 
@@ -150,8 +150,7 @@ func (w *IMAPWorker) handleMessage(msg types.WorkerMessage) error {
 
 		w.stopConnectionObserver()
 
-		c.Updates = w.updates
-		w.client = &imapClient{c, sortthread.NewThreadClient(c), sortthread.NewSortClient(c)}
+		w.newClient(c)
 
 		w.startConnectionObserver()
 
@@ -203,6 +202,11 @@ func (w *IMAPWorker) handleMessage(msg types.WorkerMessage) error {
 		reterr = errUnsupported
 	}
 
+	// we don't want idle to timeout, so set timeout to zero
+	if w.client != nil {
+		w.client.Timeout = 0
+	}
+
 	return reterr
 }
 
@@ -433,6 +437,7 @@ func (w *IMAPWorker) Run() {
 		select {
 		case msg := <-w.worker.Actions:
 			msg = w.worker.ProcessAction(msg)
+
 			if err := w.handleMessage(msg); err == errUnsupported {
 				w.worker.PostMessage(&types.Unsupported{
 					Message: types.RespondTo(msg),
@@ -443,6 +448,7 @@ func (w *IMAPWorker) Run() {
 					Error:   err,
 				}, nil)
 			}
+
 		case update := <-w.updates:
 			w.handleImapUpdate(update)
 		}