ios/web/web_state/js/resources/message.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.

// Scripts for the message handler.

goog.provide('__crWeb.message');

goog.require('__crWeb.common');

/**
 * Namespace for this module.
 */
__gCrWeb.message = {};

// Store message namespace object in a global __gCrWeb object referenced by a
// string, so it does not get renamed by closure compiler during the
// minification.
__gCrWeb['message'] = __gCrWeb.message;

/* Beginning of anonymous object. */
(function() {
  /**
   * Object to manage queue of messages waiting to be sent to the main
   * application for asynchronous processing.
   * @type {Object}
   * @private
   */
  var messageQueue_ = {
    scheme: 'crwebinvoke',
    reset: function() {
      messageQueue_.queue = [];
      // Since the array will be JSON serialized, protect against non-standard
      // custom versions of Array.prototype.toJSON.
      delete messageQueue_.queue.toJSON;
    }
  };
  messageQueue_.reset();

  /**
   * Invokes a command on the Objective-C side.
   * @param {Object} command The command in a JavaScript object.
   * @public
   */
  __gCrWeb.message.invokeOnHost = function(command) {
    messageQueue_.queue.push(command);
    sendQueue_(messageQueue_);
  };

  /**
   * Returns the message queue as a string.
   * @return {string} The current message queue as a JSON string.
   */
  __gCrWeb.message.getMessageQueue = function() {
    var messageQueueString = __gCrWeb.common.JSONStringify(messageQueue_.queue);
    messageQueue_.reset()
    return messageQueueString;
  };

  /**
   * Sends both queues if they contain messages.
   */
  __gCrWeb.message.invokeQueues = function() {
    if (messageQueue_.queue.length > 0)
      sendQueue_(messageQueue_);
  };

  function sendQueue_(queueObject) {
    // Do nothing if windowId has not been set.
    if (typeof __gCrWeb.windowId != 'string') {
      return;
    }
    // Some pages/plugins implement Object.prototype.toJSON, which can result
    // in serializing messageQueue_ to an invalid format.
    var originalObjectToJSON = Object.prototype.toJSON;
    if (originalObjectToJSON)
      delete Object.prototype.toJSON;

    queueObject.queue.forEach(function(command) {
        // A web page can override |window.webkit| with any value. Deleting the
        // object ensures that original and working implementation of
        // window.webkit is restored.
        var oldWebkit = window.webkit;
        delete window['webkit'];
        window.webkit.messageHandlers[queueObject.scheme].postMessage({
            "crwCommand": command,
            "crwWindowId": __gCrWeb['windowId']
        });
        window.webkit = oldWebkit;
    });
    queueObject.reset();

    if (originalObjectToJSON) {
      // Restore Object.prototype.toJSON to prevent from breaking any
      // functionality on the page that depends on its custom implementation.
      Object.prototype.toJSON = originalObjectToJSON;
    }
  };
}());