1 files changed, 149 insertions, 0 deletions
diff --git a/worker/imap/idler.go b/worker/imap/idler.go
new file mode 100644
index 00000000..e9aecfd9
--- /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...)...)
+}