Refactor widget postMessage API.

src/ToWidgetPostMessageApi.js

@@ -0,0 +1,86 @@
+/*
+Copyright 2018 New Vector 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.
+*/
+
+import Promise from "bluebird";
+
+// const OUTBOUND_API_NAME = 'toWidget';
+
+// Initiate requests using the "toWidget" postMessage API and handle responses
+// NOTE: ToWidgetPostMessageApi only handles message events with a data payload with a
+// response field
+export default class ToWidgetPostMessageApi {
+    constructor(timeoutMs) {
+        this._timeoutMs = timeoutMs || 5000; // default to 5s timer
+        this._counter = 0;
+        this._requestMap = {
+            // $ID: {resolve, reject}
+        };
+        this.start = this.start.bind(this);
+        this.stop = this.stop.bind(this);
+        this.onPostMessage = this.onPostMessage.bind(this);
+    }
+
+    start() {
+        window.addEventListener('message', this.onPostMessage);
+    }
+
+    stop() {
+        window.removeEventListener('message', this.onPostMessage);
+    }
+
+    onPostMessage(ev) {
+        // THIS IS ALL UNSAFE EXECUTION.
+        // We do not verify who the sender of `ev` is!
+        const payload = ev.data;
+        // NOTE: Workaround for running in a mobile WebView where a
+        // postMessage immediately triggers this callback even though it is
+        // not the response.
+        if (payload.response === undefined) {
+            return;
+        }
+        const promise = this._requestMap[payload._id];
+        if (!promise) {
+            return;
+        }
+        delete this._requestMap[payload._id];
+        promise.resolve(payload);
+    }
+
+    // Initiate outbound requests (toWidget)
+    exec(action, targetWindow, targetOrigin) {
+        targetWindow = targetWindow || window.parent; // default to parent window
+        targetOrigin = targetOrigin || "*";
+        this._counter += 1;
+        action._id = Date.now() + "-" + Math.random().toString(36) + "-" + this._counter;
+
+        return new Promise((resolve, reject) => {
+            this._requestMap[action._id] = {resolve, reject};
+            targetWindow.postMessage(action, targetOrigin);
+
+            if (this._timeoutMs > 0) {
+                setTimeout(() => {
+                    if (!this._requestMap[action._id]) {
+                        return;
+                    }
+                    console.error("postMessage request timed out. Sent object: " + JSON.stringify(action),
+                        this._requestMap);
+                    this._requestMap[action._id].reject(new Error("Timed out"));
+                    delete this._requestMap[action._id];
+                }, this._timeoutMs);
+            }
+        });
+    }
+}