From f948a8f798d9dce51c3ea035adf41a98a2e68f92 Mon Sep 17 00:00:00 2001
From: Germain <germains@element.io>
Date: Thu, 31 Aug 2023 14:36:47 +0100
Subject: [PATCH] Update member count on room summary update (#11488)

* Update member count on room summary update

* Fix performance regression for large rooms

* Update useRoomMemberCount JSDoc

* Improve throttle updates definition

* remove useCallback
---
 src/hooks/room/useRoomCallStatus.ts |  2 +-
 src/hooks/useRoomMembers.ts         | 60 +++++++++++++----------------
 2 files changed, 28 insertions(+), 34 deletions(-)

diff --git a/src/hooks/room/useRoomCallStatus.ts b/src/hooks/room/useRoomCallStatus.ts
index 1f96395a35..7afd1f9ce4 100644
--- a/src/hooks/room/useRoomCallStatus.ts
+++ b/src/hooks/room/useRoomCallStatus.ts
@@ -67,7 +67,7 @@ export const useRoomCallStatus = (
 
     const hasGroupCall = useCall(room.roomId) !== null;
 
-    const memberCount = useRoomMemberCount(room, { includeFunctional: false });
+    const memberCount = useRoomMemberCount(room);
 
     const [mayEditWidgets, mayCreateElementCalls] = useTypedEventEmitterState(
         room,
diff --git a/src/hooks/useRoomMembers.ts b/src/hooks/useRoomMembers.ts
index b9db87bc2d..f054d7337b 100644
--- a/src/hooks/useRoomMembers.ts
+++ b/src/hooks/useRoomMembers.ts
@@ -14,12 +14,11 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import { useState } from "react";
+import { useMemo, useState } from "react";
 import { Room, RoomEvent, RoomMember, RoomStateEvent } from "matrix-js-sdk/src/matrix";
 import { throttle } from "lodash";
 
 import { useTypedEventEmitter } from "./useEventEmitter";
-import { getJoinedNonFunctionalMembers } from "../utils/room/getJoinedNonFunctionalMembers";
 
 // Hook to simplify watching Matrix Room joined members
 export const useRoomMembers = (room: Room, throttleWait = 250): RoomMember[] => {
@@ -43,43 +42,38 @@ type RoomMemberCountOpts = {
      * Wait time between room member count update
      */
     throttleWait?: number;
-    /**
-     * Whether to include functional members (bots, etc...) in the room count
-     * @default true
-     */
-    includeFunctional: boolean;
 };
 
-// Hook to simplify watching Matrix Room joined member count
-export const useRoomMemberCount = (
-    room: Room,
-    opts: RoomMemberCountOpts = { throttleWait: 250, includeFunctional: true },
-): number => {
+/**
+ * Returns a count of members in a given room
+ * @param room the room to track.
+ * @param opts The options.
+ * @returns the room member count.
+ */
+export const useRoomMemberCount = (room: Room, opts: RoomMemberCountOpts = { throttleWait: 250 }): number => {
     const [count, setCount] = useState<number>(room.getJoinedMemberCount());
 
-    const { throttleWait, includeFunctional } = opts;
+    const { throttleWait } = opts;
 
-    useTypedEventEmitter(
-        room.currentState,
-        RoomStateEvent.Members,
-        throttle(
-            () => {
-                // At the time where `RoomStateEvent.Members` is emitted the
-                // summary API has not had a chance to update the `summaryJoinedMemberCount`
-                // value, therefore handling the logic locally here.
-                //
-                // Tracked as part of https://github.com/vector-im/element-web/issues/26033
-                const membersCount = includeFunctional
-                    ? room.getMembers().reduce((count, m) => {
-                          return m.membership === "join" ? count + 1 : count;
-                      }, 0)
-                    : getJoinedNonFunctionalMembers(room).length;
-                setCount(membersCount);
-            },
-            throttleWait,
-            { leading: true, trailing: true },
-        ),
+    const throttledUpdate = useMemo(
+        () =>
+            throttle(
+                () => {
+                    setCount(room.getJoinedMemberCount());
+                },
+                throttleWait,
+                { leading: true, trailing: true },
+            ),
+        [room, throttleWait],
     );
+
+    useTypedEventEmitter(room.currentState, RoomStateEvent.Members, throttledUpdate);
+
+    /**
+     * `room.getJoinedMemberCount()` caches the member count behind the room summary
+     * So we need to re-compute the member count when the summary gets updated
+     */
+    useTypedEventEmitter(room, RoomEvent.Summary, throttledUpdate);
     return count;
 };