Add postmessage api and move functions in to class

src/MatrixPostMessageApi.js

@@ -0,0 +1,101 @@
+import Promise from "bluebird";
+
+
+function defer() {
+    let resolve, reject;
+    let isPending = true;
+    let promise = new Promise(function(...args) {
+        resolve = args[0];
+        reject = args[1];
+    });
+    return {
+        resolve: function(...args) {
+            if (!isPending) {
+                return;
+            }
+            isPending = false;
+            resolve(args[0]);
+        },
+        reject: function(...args) {
+            if (!isPending) {
+                return;
+            }
+            isPending = false;
+            reject(args[0]);
+        },
+        isPending: function() {
+            return isPending;
+        },
+        promise: promise,
+    };
+}
+
+// NOTE: PostMessageApi only handles message events with a data payload with a
+// response field
+export default class PostMessageApi {
+    constructor(targetWindow, timeoutMs) {
+        this._window = targetWindow || window.parent; // default to parent window
+        this._timeoutMs = timeoutMs || 5000; // default to 5s timer
+        this._counter = 0;
+        this._pending = {
+            // $ID: Deferred
+        };
+    }
+
+    start() {
+        addEventListener('message', this.getOnMessageCallback());
+    }
+
+    stop() {
+        removeEventListener('message', this.getOnMessageCallback());
+    }
+
+    // Somewhat convoluted so we can successfully capture the PostMessageApi 'this' instance.
+    getOnMessageCallback() {
+        if (this._onMsgCallback) {
+            return this._onMsgCallback;
+        }
+        let self = this;
+        this._onMsgCallback = function(ev) {
+            // THIS IS ALL UNSAFE EXECUTION.
+            // We do not verify who the sender of `ev` is!
+            let 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;
+            }
+            let deferred = self._pending[payload._id];
+            if (!deferred) {
+                return;
+            }
+            if (!deferred.isPending()) {
+                return;
+            }
+            delete self._pending[payload._id];
+            deferred.resolve(payload);
+        };
+        return this._onMsgCallback;
+    }
+
+    exec(action, target) {
+        this._counter += 1;
+        target = target || "*";
+        action._id = Date.now() + "-" + Math.random().toString(36) + "-" + this._counter;
+        let d = defer();
+        this._pending[action._id] = d;
+        this._window.postMessage(action, target);
+
+        if (this._timeoutMs > 0) {
+            setTimeout(function() {
+                if (!d.isPending()) {
+                    return;
+                }
+                console.error("postMessage request timed out. Sent object: " + JSON.stringify(action));
+                d.reject(new Error("Timed out"));
+            }, this._timeoutMs);
+        }
+        return d.promise;
+    }
+}