From f67ccc18f4f9fef56a6ad674ef269ce281634ec2 Mon Sep 17 00:00:00 2001
From: Bruno Windels <brunow@element.io>
Date: Thu, 8 Apr 2021 12:57:10 +0200
Subject: [PATCH] take most recent member rather than first in timeline for
 inline lookup

noticed this while inspecting the code, looks related to #269
---
 .../room/timeline/persistence/MemberWriter.js | 30 +++++++++++++++----
 .../room/timeline/persistence/SyncWriter.js   |  2 +-
 2 files changed, 25 insertions(+), 7 deletions(-)

diff --git a/src/matrix/room/timeline/persistence/MemberWriter.js b/src/matrix/room/timeline/persistence/MemberWriter.js
index dc6f621d..73da64cd 100644
--- a/src/matrix/room/timeline/persistence/MemberWriter.js
+++ b/src/matrix/room/timeline/persistence/MemberWriter.js
@@ -73,7 +73,8 @@ export class MemberWriter {
         }
     }
 
-    async lookupMember(userId, timelineEvents, txn) {
+    async lookupSenderMember(event, timelineEvents, txn) {
+        const userId = event.sender;
         let member = this._cache.get(userId);
         if (!member) {
             const memberData = await txn.roomMembers.get(this._roomId, userId);
@@ -83,12 +84,21 @@ export class MemberWriter {
             }
         }
         if (!member) {
+            let memberEvent;
             // sometimes the member event isn't included in state, but rather in the timeline,
-            // even if it is not the first event in the timeline. In this case, go look for the
-            // first occurence
-            const memberEvent = timelineEvents.find(e => {
-                return e.type === MEMBER_EVENT_TYPE && e.state_key === userId;
-            });
+            // even if it is not the first event in the timeline. In this case, go look for
+            // the last one before the event
+            let foundEvent = false;
+            for (let i = timelineEvents.length - 1; i >= 0; i -= 1) {
+                const e = timelineEvents[i];
+                if (!foundEvent && e.event_id === event.event_id) {
+                    foundEvent = true;
+                }
+                if (foundEvent && e.type === MEMBER_EVENT_TYPE && e.state_key === userId) {
+                    memberEvent = e;
+                    break;
+                }
+            }
             if (memberEvent) {
                 member = RoomMember.fromMemberEvent(this._roomId, memberEvent);
             }
@@ -228,5 +238,13 @@ export function tests() {
             const change = await writer.writeTimelineMemberEvent(event, txn);
             assert(change);
         },
+        "lookupSenderMember returns closest member in the past": async assert => {
+            const event1 = createMemberEvent("join", alice, "Alice");
+            const event2 = createMemberEvent("join", alice, "Alies");
+            const writer = new MemberWriter(roomId);
+            const txn = createStorage();
+            const member = await writer.lookupSenderMember(event2, [event1, event2], txn);
+            assert.equal(member.displayName, "Alies");
+        },
     };
 }
diff --git a/src/matrix/room/timeline/persistence/SyncWriter.js b/src/matrix/room/timeline/persistence/SyncWriter.js
index a7675993..1f251fce 100644
--- a/src/matrix/room/timeline/persistence/SyncWriter.js
+++ b/src/matrix/room/timeline/persistence/SyncWriter.js
@@ -162,7 +162,7 @@ export class SyncWriter {
                 // store event in timeline
                 currentKey = currentKey.nextKey();
                 const entry = createEventEntry(currentKey, this._roomId, event);
-                let member = await this._memberWriter.lookupMember(event.sender, events, txn);
+                let member = await this._memberWriter.lookupSenderMember(event, events, txn);
                 if (member) {
                     entry.displayName = member.displayName;
                     entry.avatarUrl = member.avatarUrl;