Implement base.IPC

remoting/webapp/base/js/ipc.js

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+/**
+* @fileoverview
+*
+* In Chrome Apps, some platform APIs can only be called from the background
+* page (e.g. reloading a chrome.app.AppWindow).  Likewise, some chrome API's
+* must be initiated by user interaction, which can only be called from the
+* foreground.
+*
+* This class provides helper functions to invoke methods on different pages
+* using chrome.runtime.sendMessage.  Messages are passed in the following
+* format:
+*     {methodName:{string}, params:{Array}}
+*
+* chrome.runtime.sendMessage allows multiple handlers to be registered on a
+* document, but only one handler can send a response.
+* This class uniquely identifies a method with the |methodName| and enforces
+* that only one handler can be registered per |methodName| in the document.
+*
+* For example, to call method foo() in the background page from the foreground
+* chrome.app.AppWindow, you can do the following.
+* In the background page:
+*     base.Ipc.getInstance().register('my.service.name', foo);
+*
+* In the AppWindow document:
+*     base.Ipc.invoke('my.service.name', arg1, arg2, ...).then(
+*       function(result) {
+*         console.log('The result is ' + result);
+*     });
+*
+* This will invoke foo() with the arg1, arg2, ....
+* The return value of foo() will be passed back to the caller in the
+* form of a promise.
+*/
+
+/** @suppress {duplicate} */
+var base = base || {};
+
+(function() {
+
+'use strict';
+
+/**
+ * @constructor
+ * @private
+ */
+base.Ipc = function() {
+  base.debug.assert(instance_ === null);
+  /**
+   * @type {!Object.<Function>}
+   * @private
+   */
+  this.handlers_ = {};
+  this.onMessageHandler_ = this.onMessage_.bind(this);
+  chrome.runtime.onMessage.addListener(this.onMessageHandler_);
+};
+
+/** @private */
+base.Ipc.prototype.dispose_ = function() {
+  chrome.runtime.onMessage.removeListener(this.onMessageHandler_);
+};
+
+/**
+ * The error strings are only used for debugging purposes and are not localized.
+ *
+ * @enum {string}
+ */
+base.Ipc.Error = {
+  UNSUPPORTED_REQUEST_TYPE: 'Unsupported method name.',
+  INVALID_REQUEST_ORIGIN:
+      'base.Ipc only accept incoming requests from the same extension.'
+};
+
+/**
+ * @constructor
+ * @param {string} methodName
+ * @param {?Array} params
+ * @struct
+ * @private
+ */
+base.Ipc.Request_ = function(methodName, params) {
+  this.methodName = methodName;
+  this.params = params;
+};
+
+
+/**
+ * @param {string} methodName
+ * @param {function(*)} handler The handler can be invoked by calling
+ *   base.Ipc.invoke(|methodName|, arg1, arg2, ...)
+ * Async handlers that return promises are currently not supported.
+ * @return {boolean} Whether the handler is successfully registered.
+ */
+base.Ipc.prototype.register = function(methodName, handler) {
+  if (methodName in this.handlers_) {
+    console.error('service ' + methodName + ' is already registered.');
+    return false;
+  }
+  this.handlers_[methodName] = handler;
+  return true;
+};
+
+/**
+ * @param {string} methodName
+ */
+base.Ipc.prototype.unregister = function(methodName) {
+  delete this.handlers_[methodName];
+};
+
+/**
+ * @param {base.Ipc.Request_} message
+ * @param {chrome.runtime.MessageSender} sender
+ * @param {function(*): void} sendResponse
+ */
+base.Ipc.prototype.onMessage_ = function(message, sender, sendResponse) {
+  var methodName = message.methodName;
+  if (typeof methodName !== 'string') {
+    return;
+  }
+
+  if (sender.id !== chrome.runtime.id) {
+    sendResponse({error: base.Ipc.Error.INVALID_REQUEST_ORIGIN});
+    return;
+  }
+
+  var remoteMethod =
+      /** @type {function(*):void} */ (this.handlers_[methodName]);
+  if (!remoteMethod) {
+    sendResponse({error: base.Ipc.Error.UNSUPPORTED_REQUEST_TYPE});
+    return;
+  }
+
+  try {
+    sendResponse(remoteMethod.apply(null, message.params));
+  } catch (/** @type {Error} */ e) {
+    sendResponse({error: e.message});
+  }
+};
+
+/**
+ * Invokes a method on a remote page
+ *
+ * @param {string} methodName
+ * @param {...} var_args
+ * @return A Promise that would resolve to the return value of the handler or
+ *   reject if the handler throws an exception.
+ */
+base.Ipc.invoke = function(methodName, var_args) {
+  var params = Array.prototype.slice.call(arguments, 1);
+  var sendMessage = base.Promise.as(
+      chrome.runtime.sendMessage,
+      [null, new base.Ipc.Request_(methodName, params)]);
+
+  return sendMessage.then(
+    /** @param {?{error: Error}} response */
+    function(response) {
+      if (response && response.error) {
+        return Promise.reject(response.error);
+      } else {
+        return Promise.resolve(response);
+      }
+  });
+};
+
+
+/** @type {base.Ipc} */
+var instance_ = null;
+
+/** @return {base.Ipc} */
+base.Ipc.getInstance = function() {
+  if (!instance_) {
+    instance_ = new base.Ipc();
+  }
+  return instance_;
+};
+
+base.Ipc.deleteInstance = function() {
+  if (instance_) {
+    instance_.dispose_();
+    instance_ = null;
+  }
+};
+
+})();