Hopefully read DM rooms from account data

src/DMRoomMap.js

@@ -0,0 +1,46 @@
+/*
+Copyright 2016 OpenMarket Ltd
+
+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.
+*/
+
+/**
+ * Class that takes a Matrix Client and flips the m.direct map
+ * so the operation of mapping a room ID to which user it's a DM
+ * with can be performed efficiently.
+ */
+export default class DMRoomMap {
+    constructor(matrixClient) {
+        const mDirectEvent = matrixClient.getAccountData('m.direct');
+        if (!mDirectEvent) {
+            this.userToRooms = {};
+            this.roomToUser = {};
+        } else {
+            this.userToRooms = mDirectEvent.getContent();
+            this.roomToUser = {};
+            for (const user of Object.keys(this.userToRooms)) {
+                for (const roomId of this.userToRooms[user]) {
+                    this.roomToUser[roomId] = user;
+                }
+            }
+        }
+    }
+
+    getDMRoomsForUserId(userId) {
+        return this.userToRooms[userId];
+    }
+
+    getUserIdForRoomId(roomId) {
+        return this.roomToUser[roomId];
+    }
+}