implement heroes logic to calculate the room name

src/matrix/room/members/Heroes.js

@@ -0,0 +1,101 @@
+/*
+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 {RoomMember} from "./RoomMember.js";
+
+function calculateRoomName(sortedMembers, summary) {
+    const countWithoutMe = summary.joinCount + summary.inviteCount - 1;
+    if (sortedMembers.length >= countWithoutMe) {
+        if (sortedMembers.length > 1) {
+            const lastMember = sortedMembers[sortedMembers.length - 1];
+            const firstMembers = sortedMembers.slice(0, sortedMembers.length - 1);
+            return firstMembers.map(m => m.displayName).join(", ") + " and " + lastMember.displayName;
+        } else {
+            return sortedMembers[0].displayName;
+        }
+    } else if (sortedMembers.length < countWithoutMe) {
+        return sortedMembers.map(m => m.displayName).join(", ") + ` and ${countWithoutMe} others`;
+    } else {
+        // Empty Room
+        return null;
+    }
+}
+
+export class Heroes {
+    constructor(roomId) {
+        this._roomId = roomId;
+        this._members = new Map();
+    }
+
+    /**
+     * @param  {string[]} newHeroes      array of user ids
+     * @param  {RoomMember[]} changedMembers array of changed members in this sync
+     * @param  {Transaction} txn
+     * @return {Promise}
+     */
+    async calculateChanges(newHeroes, changedMembers, txn) {
+        const updatedHeroMembers = new Map();
+        const removedUserIds = [];
+        // remove non-present members
+        for (const existingUserId of this._members.keys()) {
+            if (newHeroes.indexOf(existingUserId) === -1) {
+                removedUserIds.push(existingUserId);
+            }
+        }
+        // update heroes with synced member changes
+        for (const member of changedMembers) {
+            if (this._members.has(member.userId) || newHeroes.indexOf(member.userId) !== -1) {
+                updatedHeroMembers.set(member.userId, member);
+            }
+        }
+        // load member for new heroes from storage
+        for (const userId of newHeroes) {
+            if (!this._members.has(userId) && !updatedHeroMembers.has(userId)) {
+                const memberData = await txn.roomMembers.get(this._roomId, userId);
+                if (memberData) {
+                    const member = new RoomMember(memberData);
+                    updatedHeroMembers.set(member.userId, member);
+                }
+            }
+        }
+        return {updatedHeroMembers: updatedHeroMembers.values(), removedUserIds};
+    }
+
+    applyChanges({updatedHeroMembers, removedUserIds}, summary) {
+        for (const userId of removedUserIds) {
+            this._members.delete(userId);
+        }
+        for (const member of updatedHeroMembers) {
+            this._members.set(member.userId, member);
+        }
+        const sortedMembers = Array.from(this._members.values()).sort((a, b) => a.displayName.localeCompare(b.displayName));
+        this._roomName = calculateRoomName(sortedMembers, summary);
+    }
+
+    get roomName() {
+        return this._roomName;
+    }
+
+    get roomAvatarUrl() {
+        if (this._members.size === 1) {
+            for (const member of this._members.values()) {
+                console.log("roomAvatarUrl", member, member.avatarUrl);
+                return member.avatarUrl;
+            }
+        }
+        return null;
+    }
+}