From e5b339702a56fa02dedec770a79b64313fb30108 Mon Sep 17 00:00:00 2001
From: Koni Marti <koni.marti@gmail.com>
Date: Sat, 30 Apr 2022 01:08:56 +0200
Subject: imap: monitor the logout channel with an observer

Untangle the observer functionality from the message handling routine.
Observe the imap client's logout channel and trigger a connection error
when necessary to start the reconnect cycle.

Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>
---
 worker/imap/observer.go | 152 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 152 insertions(+)
 create mode 100644 worker/imap/observer.go

(limited to 'worker/imap/observer.go')

diff --git a/worker/imap/observer.go b/worker/imap/observer.go
new file mode 100644
index 00000000..e49744cc
--- /dev/null
+++ b/worker/imap/observer.go
@@ -0,0 +1,152 @@
+package imap
+
+import (
+	"fmt"
+	"math"
+	"sync"
+	"time"
+
+	"git.sr.ht/~rjarry/aerc/worker/types"
+	"github.com/emersion/go-imap"
+)
+
+// observer monitors the loggedOut channel of the imap client. If the logout
+// signal is received, the observer will emit a connection error to the ui in
+// order to start the reconnect cycle.
+type observer struct {
+	sync.Mutex
+	config        imapConfig
+	client        *imapClient
+	worker        *types.Worker
+	done          chan struct{}
+	autoReconnect bool
+	retries       int
+	running       bool
+}
+
+func newObserver(cfg imapConfig, w *types.Worker) *observer {
+	return &observer{config: cfg, worker: w, done: make(chan struct{})}
+}
+
+func (o *observer) SetClient(c *imapClient) {
+	o.Stop()
+	o.Lock()
+	o.client = c
+	o.Unlock()
+	o.Start()
+	o.retries = 0
+}
+
+func (o *observer) SetAutoReconnect(auto bool) {
+	o.autoReconnect = auto
+}
+
+func (o *observer) AutoReconnect() bool {
+	return o.autoReconnect
+}
+
+func (o *observer) isClientConnected() bool {
+	o.Lock()
+	defer o.Unlock()
+	return o.client != nil && o.client.State() == imap.SelectedState
+}
+
+func (o *observer) EmitIfNotConnected() bool {
+	if !o.isClientConnected() {
+		o.emit("imap client not connected: attempt reconnect")
+		return true
+	}
+	return false
+}
+
+func (o *observer) IsRunning() bool {
+	return o.running
+}
+
+func (o *observer) Start() {
+	if o.running {
+		o.log("runs already")
+		return
+	}
+	if o.client == nil {
+		return
+	}
+	if o.EmitIfNotConnected() {
+		return
+	}
+	go func() {
+		select {
+		case <-o.client.LoggedOut():
+			o.log("<-logout")
+			if o.autoReconnect {
+				o.emit("logged out")
+			} else {
+				o.log("ignore logout (auto-reconnect off)")
+			}
+		case <-o.done:
+			o.log("<-done")
+		}
+		o.running = false
+		o.log("stopped")
+	}()
+	o.running = true
+	o.log("started")
+}
+
+func (o *observer) Stop() {
+	if o.client == nil {
+		return
+	}
+	if o.done != nil {
+		close(o.done)
+	}
+	o.done = make(chan struct{})
+	o.running = false
+}
+
+func (o *observer) DelayedReconnect() error {
+	if o.client == nil {
+		return nil
+	}
+	var wait time.Duration
+	var reterr error
+
+	if o.retries > 0 {
+		backoff := int(math.Pow(1.8, float64(o.retries)))
+		var err error
+		wait, err = time.ParseDuration(fmt.Sprintf("%ds", backoff))
+		if err != nil {
+			return err
+		}
+		if wait > o.config.reconnect_maxwait {
+			wait = o.config.reconnect_maxwait
+		}
+
+		reterr = fmt.Errorf("reconnect in %v", wait)
+	} else {
+		reterr = fmt.Errorf("reconnect")
+	}
+
+	go func() {
+		<-time.After(wait)
+		o.emit(reterr.Error())
+	}()
+
+	o.retries++
+	return reterr
+}
+
+func (o *observer) emit(errMsg string) {
+	o.log("disconnect done->")
+	o.worker.PostMessage(&types.Done{
+		Message: types.RespondTo(&types.Disconnect{})}, nil)
+	o.log("connection error->")
+	o.worker.PostMessage(&types.ConnError{
+		Error: fmt.Errorf(errMsg),
+	}, nil)
+}
+
+func (o *observer) log(args ...interface{}) {
+	header := fmt.Sprintf("observer (%p) [running:%t]", o, o.running)
+	o.worker.Logger.Println(append([]interface{}{header}, args...)...)
+}
-- 
cgit