From 09bc5379b7244a943bef92465cce59e624c573f7 Mon Sep 17 00:00:00 2001
From: Simon THOBY <git@nightmared.fr>
Date: Sun, 14 Aug 2022 16:40:27 +0200
Subject: [PATCH] matrix: stop updating the global display names

We can afford to do that (which should stress less the [matrix]
homeservers) because we no longer drop all the user displaynames
across all channels) when we see a Leave or Ban membership event
---
 bridge/matrix/handlers.go | 20 ++++++++++----------
 bridge/matrix/helpers.go  | 23 +++++++++--------------
 2 files changed, 19 insertions(+), 24 deletions(-)

diff --git a/bridge/matrix/handlers.go b/bridge/matrix/handlers.go
index 8833b0ed..c6df3bec 100644
--- a/bridge/matrix/handlers.go
+++ b/bridge/matrix/handlers.go
@@ -75,15 +75,6 @@ func (b *Bmatrix) handleEvent(origin EventOrigin, ev *event.Event) {
 		b.Unlock()
 	}
 
-	// if we receive messages both via the classical matrix syncer and appserver, prefer appservice and throw away this duplicate event
-	if channel.appService && origin != originAppService {
-		b.Log.Debugf("Dropping event, should receive it via appservice: %s", ev.ID)
-
-		return
-	}
-
-	b.Log.Debugf("== Receiving event: %#v (appService=%t)", ev, origin == originAppService)
-
 	if ev.Type == event.EphemeralEventTyping {
 		typing := ev.Content.AsTyping()
 		if len(typing.UserIDs) > 0 {
@@ -98,6 +89,15 @@ func (b *Bmatrix) handleEvent(origin EventOrigin, ev *event.Event) {
 		return
 	}
 
+	// if we receive messages both via the classical matrix syncer and appserver, prefer appservice and throw away this duplicate event
+	if channel.appService && origin != originAppService {
+		b.Log.Debugf("Dropping event, should receive it via appservice: %s", ev.ID)
+
+		return
+	}
+
+	b.Log.Debugf("== Receiving event: %#v (appService=%t)", ev, origin == originAppService)
+
 	defer (func(ev *event.Event) {
 		// not crucial, so no ratelimit check here
 		if err := b.mc.MarkRead(ev.RoomID, ev.ID); err != nil {
@@ -146,7 +146,7 @@ func (b *Bmatrix) handleMemberChange(ev *event.Event) {
 	if member.Membership == event.MembershipJoin {
 		b.cacheDisplayName(ev.RoomID, ev.Sender, member.Displayname)
 	} else if member.Membership == event.MembershipLeave || member.Membership == event.MembershipBan {
-		b.removeDisplayNameFromCache(ev.Sender)
+		b.removeDisplayNameFromCache(ev.Sender, ev.RoomID)
 	}
 }
 
diff --git a/bridge/matrix/helpers.go b/bridge/matrix/helpers.go
index 93031e1d..bc9ca403 100644
--- a/bridge/matrix/helpers.go
+++ b/bridge/matrix/helpers.go
@@ -88,9 +88,6 @@ func (c *NicknameCache) retrieveDisplaynameFromCache(channelID id.RoomID, mxid i
 	}
 
 	if cachedEntry.conflictWithOtherUsername {
-		// TODO: the current behavior is that only users with clashing usernames and *that have
-		// spoken since the bridge started* will get their mxids shown, and this doesn't
-		// feel right
 		return fmt.Sprintf("%s (%s)", cachedEntry.displayName, mxid)
 	}
 
@@ -232,18 +229,11 @@ func (b *Bmatrix) cacheDisplayName(channelID id.RoomID, mxid id.UserID, displayN
 		conflictWithOtherUsername: conflict,
 	}
 
-	// this is a local (room-specific) display name, let's cache it as such
 	if channelID == "" {
 		newEntry.globalEntry = &cacheEntry
 	} else {
-		globalDisplayName := b.retrieveGlobalDisplayname(mxid)
-		// updating the global display name or resetting the room name to the global name
-		if globalDisplayName == displayName {
-			delete(newEntry.perChannel, channelID)
-			newEntry.globalEntry = &cacheEntry
-		} else {
-			newEntry.perChannel[channelID] = cacheEntry
-		}
+		// this is a local (room-specific) display name, let's cache it as such
+		newEntry.perChannel[channelID] = cacheEntry
 	}
 
 	cache.users[mxid] = newEntry
@@ -251,13 +241,18 @@ func (b *Bmatrix) cacheDisplayName(channelID id.RoomID, mxid id.UserID, displayN
 	return displayName
 }
 
-func (b *Bmatrix) removeDisplayNameFromCache(mxid id.UserID) {
+func (b *Bmatrix) removeDisplayNameFromCache(mxid id.UserID, roomID id.RoomID) {
 	cache := b.NicknameCache
 
 	cache.Lock()
 	defer cache.Unlock()
 
-	delete(cache.users, mxid)
+	if user, userPresent := cache.users[mxid]; userPresent {
+		if _, roomPresent := user.perChannel[roomID]; roomPresent {
+			delete(user.perChannel, roomID)
+			cache.users[mxid] = user
+		}
+	}
 }
 
 // getAvatarURL returns the avatar URL of the specified sender.