From d2791094d90359c84c6bf103e6ca36ce9b96ee20 Mon Sep 17 00:00:00 2001
From: Alex Auvolat <alex@adnab.me>
Date: Sun, 1 Mar 2020 20:37:34 +0100
Subject: [PATCH] Update how mattermost connector works to be more resilient to
 deco

---
 connector/mattermost/mattermost.go | 71 ++++++++++++++++++++----------
 1 file changed, 48 insertions(+), 23 deletions(-)

diff --git a/connector/mattermost/mattermost.go b/connector/mattermost/mattermost.go
index 6c0e091..0a632a9 100644
--- a/connector/mattermost/mattermost.go
+++ b/connector/mattermost/mattermost.go
@@ -42,6 +42,7 @@ type mmCaches struct {
 	mmusers     map[string]string // map mm username to mm user id
 	sentjoined  map[string]bool   // map username/room name to bool
 	displayname map[UserID]string // map username to last displayname
+	initsynced  map[string]bool   // chans for which init sync has been done
 }
 
 func (mm *Mattermost) SetHandler(h Handler) {
@@ -57,6 +58,15 @@ func (mm *Mattermost) Configure(c Configuration) error {
 		mm.Close()
 	}
 
+	// Reinitialize shared data structures
+	mm.handlerStopChan = make(chan bool)
+
+	mm.caches.mmusers = make(map[string]string)
+	mm.caches.sentjoined = make(map[string]bool)
+	mm.caches.displayname = make(map[UserID]string)
+	mm.caches.initsynced = make(map[string]bool)
+
+	// Read config
 	var err error
 
 	mm.server, err = c.GetString("server")
@@ -100,23 +110,23 @@ func (mm *Mattermost) Configure(c Configuration) error {
 	if token != "" {
 		password = "token=" + token
 	}
+
+	// Try to log in
 	mm.conn = matterclient.New(mm.username, password, anyteam, mm.server)
 	mm.conn.Credentials.NoTLS = notls
 	err = mm.conn.Login()
 	if err != nil {
 		return err
 	}
+
+	// Try to start listening for messages
+	// Everytime the listener reconnects, mm.handleConnected does a sync of room status
+	mm.conn.OnWsConnect = mm.handleConnected
 	go mm.conn.WsReceiver()
 	go mm.conn.StatusLoop()
+	go mm.handleLoop(mm.conn.MessageChan, mm.handlerStopChan)
 
-	for i := 0; i < 42; i++ {
-		time.Sleep(time.Duration(1) * time.Second)
-		if mm.conn.WsConnected {
-			mm.handleConnected()
-			return nil
-		}
-	}
-	return fmt.Errorf("Failed to connect after 42s attempting")
+	return nil
 }
 
 func (mm *Mattermost) User() UserID {
@@ -319,17 +329,7 @@ func (mm *Mattermost) Close() {
 }
 
 func (mm *Mattermost) handleConnected() {
-	// Reinitialize shared data structures
-	mm.handlerStopChan = make(chan bool)
-
-	mm.caches.mmusers = make(map[string]string)
-	mm.caches.sentjoined = make(map[string]bool)
-	mm.caches.displayname = make(map[UserID]string)
-
-	log.Debugf("Connected to mattermost: %s@%s\n", mm.username, mm.server)
-
-	// Handle incoming messages
-	go mm.handleLoop(mm.conn.MessageChan, mm.handlerStopChan)
+	log.Debugf("(Re-)connected to mattermost: %s@%s ; doing channel sync\n", mm.username, mm.server)
 
 	// Initial channel sync
 	chans := mm.conn.GetChannels()
@@ -337,20 +337,43 @@ func (mm *Mattermost) handleConnected() {
 	for _, ch := range chans {
 		if _, ok := doneCh[ch.Id]; !ok {
 			doneCh[ch.Id] = true
-			go mm.initSyncChannel(ch)
+			go mm.syncChannel(ch)
 		}
 	}
 }
 
+func (mm *Mattermost) syncChannel(ch *model.Channel) {
+	// The first time we see a chan, sync everything (member list, names, profile pictures)
+	must_initsync := func() bool {
+		mm.caches.Lock()
+		defer mm.caches.Unlock()
+
+		if x, ok := mm.caches.initsynced[ch.Id]; ok && x {
+			return false
+		}
+		mm.caches.initsynced[ch.Id] = true
+		return true
+	}()
+
+	if must_initsync {
+		mm.initSyncChannel(ch)
+	}
+
+	// The following times, only sync missing messages
+	mm.backlogChannel(ch)
+}
+
 func (mm *Mattermost) initSyncChannel(ch *model.Channel) {
 	if len(strings.Split(ch.Name, "__")) == 2 {
 		// DM channel
 		// Update remote user info
 		users := strings.Split(ch.Name, "__")
 		for _, uid := range users {
-			user := mm.conn.GetUser(uid)
-			if user != nil && uid != mm.conn.User.Id {
-				mm.updateUserInfo(user)
+			if uid != mm.conn.User.Id {
+				user := mm.conn.GetUser(uid)
+				if user != nil {
+					mm.updateUserInfo(user)
+				}
 			}
 		}
 	} else {
@@ -415,7 +438,9 @@ func (mm *Mattermost) initSyncChannel(ch *model.Channel) {
 			log.Warnf("Could not get channel members: %s", resp.Error.Error())
 		}
 	}
+}
 
+func (mm *Mattermost) backlogChannel(ch *model.Channel) {
 	// Read backlog
 	last_seen_post := mm.handler.CacheGet(fmt.Sprintf("last_seen_%s", ch.Id))
 	if last_seen_post != "" {