Convert shim to Typescript (#32)

ext/src/shim/messageBridge.ts

@@ -0,0 +1,45 @@
+"use strict";
+
+import { Message } from "../types";
+
+type ListenerFunc = (message: Message) => void;
+
+
+export function onMessage (listener: ListenerFunc) {
+    document.addEventListener("__castMessage", (ev: CustomEvent) => {
+        listener(JSON.parse(ev.detail));
+
+        /**
+         * TODO:
+         * Figure out a way to handle and stop propagation of this
+         * event to hide it from page scripts.
+         * Currently the event handler is set after the page loads the
+         * cast API, allowing pages set handlers before this script,
+         * intercept the event, and cancel it.
+         */
+        ev.stopPropagation();
+    }, true);
+}
+
+export function sendMessageResponse (message: Message) {
+    const event = new CustomEvent("__castMessageResponse", {
+        detail: JSON.stringify(message)
+    });
+
+    document.dispatchEvent(event);
+}
+
+
+export function onMessageResponse (listener: ListenerFunc) {
+    document.addEventListener("__castMessageResponse", (ev: CustomEvent) => {
+        listener(JSON.parse(ev.detail));
+    }, true);
+}
+
+export function sendMessage (message: Message) {
+    const event = new CustomEvent("__castMessage", {
+        detail: JSON.stringify(message)
+    });
+
+    document.dispatchEvent(event);
+}