Convert LocalEchoWrapper to TS

src/settings/handlers/LocalEchoWrapper.ts

@@ -0,0 +1,70 @@
+/*
+Copyright 2017 Travis Ralston
+Copyright 2019, 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 SettingsHandler from "./SettingsHandler";
+
+/**
+ * A wrapper for a SettingsHandler that performs local echo on
+ * changes to settings. This wrapper will use the underlying
+ * handler as much as possible to ensure values are not stale.
+ */
+export default class LocalEchoWrapper extends SettingsHandler {
+    private cache: {
+        [settingName: string]: {
+            [roomId: string]: any;
+        };
+    } = {};
+
+    /**
+     * Creates a new local echo wrapper
+     * @param {SettingsHandler} handler The handler to wrap
+     */
+    constructor(private handler: SettingsHandler) {
+        super();
+    }
+
+    public getValue(settingName: string, roomId: string): any {
+        const cacheRoomId = roomId ? roomId : "UNDEFINED"; // avoid weird keys
+        const bySetting = this.cache[settingName];
+        if (bySetting && bySetting.hasOwnProperty(cacheRoomId)) {
+            return bySetting[cacheRoomId];
+        }
+
+        return this.handler.getValue(settingName, roomId);
+    }
+
+    public setValue(settingName: string, roomId: string, newValue: any): Promise<void> {
+        if (!this.cache[settingName]) this.cache[settingName] = {};
+        const bySetting = this.cache[settingName];
+
+        const cacheRoomId = roomId ? roomId : "UNDEFINED"; // avoid weird keys
+        bySetting[cacheRoomId] = newValue;
+
+        const handlerPromise = this.handler.setValue(settingName, roomId, newValue);
+        return Promise.resolve(handlerPromise).finally(() => {
+            delete bySetting[cacheRoomId];
+        });
+    }
+
+    public canSetValue(settingName, roomId): boolean {
+        return this.handler.canSetValue(settingName, roomId);
+    }
+
+    public isSupported(): boolean {
+        return this.handler.isSupported();
+    }
+}