Issue 1663 - Emulate background page and implement proper message responder

ext/content.js

 /*
  * This file is part of Adblock Plus <http://adblockplus.org/>,
  * Copyright (C) 2006-2014 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 (function(global)
 {
   if (!global.ext)
     global.ext = {};
 
-  function updateFromURL(data)
+  var backgroundFrame = document.createElement("iframe");
+  backgroundFrame.setAttribute("src", "background.html" + window.location.search);
+  backgroundFrame.style.display = "none";
+  window.addEventListener("DOMContentLoaded", function()
   {
-    if (window.location.search)
+    document.body.appendChild(backgroundFrame);
+  }, false);
+
+  var messageQueue = [];
+  var maxMessageId = -1;
+  var loadHandler = function(event)
+  {
+    if (event.data.type == "backgroundPageLoaded")
     {
-      var params = window.location.search.substr(1).split("&");
-      for (var i = 0; i < params.length; i++)
-      {
-        var parts = params[i].split("=", 2);
-        if (parts.length == 2 && parts[0] in data)
-          data[parts[0]] = decodeURIComponent(parts[1]);
-      }
+      var queue = messageQueue;
+      messageQueue = null;
+      if (queue)
+        for (var i = 0; i < queue.length; i++)
+          backgroundFrame.contentWindow.postMessage(queue[i], "*");
+      window.removeEventListener("message", loadHandler, false);
     }
   }
-
-  var subscriptions =[
-    "https://easylist-downloads.adblockplus.org/easylistgermany+easylist.txt",
-    "https://easylist-downloads.adblockplus.org/exceptionrules.txt",
-    "https://easylist-downloads.adblockplus.org/fanboy-social.txt"
-  ];
-
-  var listenerFilter = null;
+  window.addEventListener("message", loadHandler, false);
 
   global.ext.backgroundPage = {
     sendMessage: function(message, responseCallback)
     {
-      var respond = function(response)
+      var rawMessage = {
+        type: "message",
+        messageId: ++maxMessageId,
+        payload: message
+      };
+      if (messageQueue)
+        messageQueue.push(rawMessage);
+      else
+        backgroundFrame.contentWindow.postMessage(rawMessage, "*");
+
+      if (responseCallback)
       {
-        setTimeout(responseCallback.bind(responseCallback, response), 0);
-      };
-
-      var dispatchListenerNotification = function(action)
-      {
-        var match = /^subscription\.(.*)/.exec(action);
-        if (match && listenerFilter && listenerFilter.indexOf(match[1]) >= 0)
+        var callbackWrapper = function(event)
         {
-          global.ext.onMessage._dispatch({
-            type: "subscriptions.listen",
-            action: match[1],
-            args: Array.prototype.slice.call(arguments, 1)
-          });
-        }
-      };
-
-      switch (message.type)
-      {
-        case "app.get":
-          if (message.what == "issues")
+          if (event.data.type == "response" && event.data.messageId == rawMessage.messageId)
           {
-            var response = {seenDataCorruption: false, filterlistsReinitialized: false};
-            updateFromURL(response);
-
-            var info = {platform: "gecko", platformVersion: "34.0", application: "firefox", applicationVersion: "34.0"};
-            updateFromURL(info);
-            response.legacySafariVersion = (info.platform == "safari" && (
-              parseInt(info.platformVersion, 10) < 6 ||  // beforeload breaks websites in Safari 5
-              info.platformVersion == "6.1" ||           // extensions are broken in 6.1 and 7.0
-              info.platformVersion == "7.0"));
-
-            respond(response);
+            window.removeEventListener("message", callbackWrapper, false);
+            responseCallback(event.data.payload);
           }
-          else if (message.what == "doclink")
-            respond("https://adblockplus.org/redirect?link=" + encodeURIComponent(message.link));
-          else
-            respond(null);
-          break;
-        case "app.open":
-          if (message.what == "options")
-            window.open("http://example.com/options.html", "_blank");
-          break;
-        case "subscriptions.get":
-          respond(subscriptions);
-          break;
-        case "filters.blocked":
-          var params = {blockedURLs: ""};
-          updateFromURL(params);
-          var blocked = params.blockedURLs.split(",");
-          respond(blocked.indexOf(message.url) >= 0);
-          break;
-        case "subscriptions.toggle":
-          var index = subscriptions.indexOf(message.url);
-          if (index >= 0)
-          {
-            subscriptions.splice(index, 1);
-            dispatchListenerNotification("subscription.removed", message.url);
-          }
-          else
-          {
-            subscriptions.push(message.url);
-            dispatchListenerNotification("subscription.added", message.url);
-          }
-          break;
-        case "subscriptions.listen":
-          listenerFilter = message.filter;
-          break;
+        };
+        window.addEventListener("message", callbackWrapper, false);
       }
     }
   };
-
-  var EventTarget = function(cancelable)
-  {
-    this._listeners = [];
-    this._cancelable = cancelable;
-  };
-  EventTarget.prototype = {
-    addListener: function(listener)
-    {
-      if (this._listeners.indexOf(listener) == -1)
-        this._listeners.push(listener);
-    },
-    removeListener: function(listener)
-    {
-      var idx = this._listeners.indexOf(listener);
-      if (idx != -1)
-        this._listeners.splice(idx, 1);
-    },
-    _dispatch: function()
-    {
-      var result = null;
-
-      for (var i = 0; i < this._listeners.length; i++)
-      {
-        result = this._listeners[i].apply(null, arguments);
-
-        if (this._cancelable && result === false)
-          break;
-      }
-
-      return result;
-    }
-  };
-  global.ext.onMessage = new EventTarget();
 })(this);