base impl of member list

src/matrix/room/Room.js

@@ -23,6 +23,7 @@ import {FragmentIdComparer} from "./timeline/FragmentIdComparer.js";
 import {SendQueue} from "./sending/SendQueue.js";
 import {WrappedError} from "../error.js"
 import {RoomMember} from "./members/RoomMember.js";
+import {MemberList} from "./members/MemberList.js";
 
 export class Room extends EventEmitter {
 	constructor({roomId, storage, hsApi, emitCollectionChange, sendScheduler, pendingEvents, user}) {

src/matrix/room/members/MemberList.js

@@ -0,0 +1,49 @@
+/*
+Copyright 2020 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import {ObservableMap} from "../../../observable/map/ObservableMap.js";
+
+export class MemberList {
+    constructor({members, closeCallback}) {
+        this._members = new ObservableMap();
+        for (const member of members) {
+            this._members.add(member.userId, member);
+        }
+        this._closeCallback = closeCallback;
+        this._retentionCount = 1;
+    }
+
+    afterSync(updatedMembers) {
+        for (const member of updatedMembers) {
+            this._members.add(member.userId, member);
+        }
+    }
+
+    get members() {
+        return this._members;
+    }
+
+    retain() {
+        this._retentionCount += 1;
+    }
+
+    release() {
+        this._retentionCount -= 1;
+        if (this._retentionCount === 0) {
+            this._closeCallback();
+        }
+    }
+}