Issue 3862 - Add EventEmitter class and implement in the FilterNotifier

lib/filterNotifier.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 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/>.
  */
 
 /**
  * @fileOverview This component manages listeners and calls them to distributes
  * messages about filter changes.
  */
 
-/**
- * List of registered listeners
- * @type function[]
- */
-let listeners = [];
+let {EventEmitter} = require("events");
+
+const CATCH_ALL = "__all";
 
 /**
  * This class allows registering and triggering listeners for filter events.
  * @class
  */
-let FilterNotifier = exports.FilterNotifier =
+exports.FilterNotifier =
 {
+  __proto__: new EventEmitter(),
+
   /**
    * Adds a listener
+   *
+   * @deprecated use FilterNotifier.on(action, callback)
    */
   addListener: function(/**function(action, item, newValue, oldValue)*/ listener)
   {
-    if (listeners.indexOf(listener) >= 0)
-      return;
-
-    listeners.push(listener);
+    let listeners = this._listeners[CATCH_ALL];
+    if (!listeners || listeners.indexOf(listener) == -1)
+      this.on(CATCH_ALL, listener);
   },
 
   /**
    * Removes a listener that was previosly added via addListener
+   *
+   * @deprecated use FilterNotifier.off(action, callback)
    */
   removeListener: function(/**function(action, item, newValue, oldValue)*/ listener)
   {
-    let index = listeners.indexOf(listener);
-    if (index >= 0)
-      listeners.splice(index, 1);
+    this.off(CATCH_ALL, listener);
   },
 
   /**
    * Notifies listeners about an event
    * @param {String} action event code ("load", "save", "elemhideupdate",
    *                 "subscription.added", "subscription.removed",
    *                 "subscription.disabled", "subscription.title",
    *                 "subscription.lastDownload", "subscription.downloadStatus",
    *                 "subscription.homepage", "subscription.updated",
    *                 "filter.added", "filter.removed", "filter.moved",
    *                 "filter.disabled", "filter.hitCount", "filter.lastHit")
    * @param {Subscription|Filter} item item that the change applies to
+   * @deprecated use FilterNotifier.emit(action)
    */
   triggerListeners: function(action, item, param1, param2, param3)
   {
-    let list = listeners.slice();
-    for (let listener of list)
-      listener(action, item, param1, param2, param3);
+    this.emit(action, item, param1, param2, param3);
+    this.emit(CATCH_ALL, action, item, param1, param2, param3);
   }
 };