EventEmitter: inherit from Node's EventEmitter

This reduces code duplication by using a well known/tested module:
  http://nodejs.org/api/events.html

This also preserves most of the public API:
  http://sipjs.com/api/0.6.0/eventEmitter/

See below for more details:

* #on, #once and #off do NOT take third arguments (bindTarget)

  listeners should be explicitly bound to their objects before passing to
  EventEmitter methods

* #setMaxListeners works like Node's

  - does NOT prevent extra listeners
  - passing 0 allows unlimited listeners

* #emit no longer returns `this`, works like Node's

* #checkListener has been removed

  The rest of SIP.js uses:

    emitter.listeners(eventName).length

  instead of:

    emitter.checkListener(eventName)

* remove all other methods and their tests

Supporting changes:

* test/spec/SpecSession.js: define .logger on the constructed Session

  This prevents tests from failing
  due to an artificially constructed Session's logger being undefined
  since the Session no longer has a logger by virtue of being an EventEmitter

* src/Session.js: fix the following methods to correctly return `this`:

  - failed
  - rejected
  - canceled
  - accepted
  - terminated
  - connecting

Author: joseph-onsip

src/ClientContext.js

@@ -3,14 +3,7 @@ module.exports = function (SIP) {
 var ClientContext;
 
 ClientContext = function (ua, method, target, options) {
-  var originalTarget = target,
-      events = [
-        'progress',
-        'accepted',
-        'rejected',
-        'failed',
-        'cancel'
-      ];
+  var originalTarget = target;
 
   // Validate arguments
   if (target === undefined) {
@@ -54,7 +47,6 @@ ClientContext = function (ua, method, target, options) {
   this.localIdentity = this.request.from;
   this.remoteIdentity = this.request.to;
 
-  this.initEvents(events);
   this.data = {};
 };
 ClientContext.prototype = new SIP.EventEmitter();

src/Dialogs.js

@@ -92,7 +92,6 @@ Dialog = function(owner, message, type, state) {
   this.owner = owner;
   owner.ua.dialogs[this.id.toString()] = this;
   this.logger.log('new ' + type + ' dialog created with status ' + (this.state === C.STATUS_EARLY ? 'EARLY': 'CONFIRMED'));
-  owner.initMoreEvents(['dialog']);
   owner.emit('dialog', this);
 };
 

src/EventEmitter.js

@@ -1,202 +1,16 @@
 "use strict";
-/**
- * @fileoverview EventEmitter
- */
+var NodeEventEmitter = require('events').EventEmitter;
 
-/**
- * @augments SIP
- * @class Class creating an event emitter.
- */
-module.exports = function (SIP) {
-var
-  EventEmitter,
-  logger = new SIP.LoggerFactory().getLogger('sip.eventemitter'),
-  C = {
-    MAX_LISTENERS: 10
-  };
+function EventEmitter () {}
 
-EventEmitter = function(){};
-EventEmitter.prototype = {
-  /**
-   * Initialize events dictionaries.
-   * @param {Array} events
-   */
-  initEvents: function(events) {
-    this.events = {};
+EventEmitter.prototype = Object.create(NodeEventEmitter.prototype);
 
-    return this.initMoreEvents(events);
-  },
-
-  initMoreEvents: function(events) {
-    var idx;
-
-    if (!this.logger) {
-      this.logger = logger;
-    }
-
-    this.maxListeners = C.MAX_LISTENERS;
-
-    for (idx = 0; idx < events.length; idx++) {
-      if (!this.events[events[idx]]) {
-        this.logger.log('adding event '+ events[idx]);
-        this.events[events[idx]] = [];
-      } else {
-        this.logger.log('skipping event '+ events[idx]+ ' - Event exists');
-      }
-    }
-
-    return this;
-  },
-
-  /**
-  * Check whether an event exists or not.
-  * @param {String} event
-  * @returns {Boolean}
-  */
-  checkEvent: function(event) {
-    return !!(this.events && this.events[event]);
-  },
-
-  /**
-  * Check whether an event exists and has at least one listener or not.
-  * @param {String} event
-  * @returns {Boolean}
-  */
-  checkListener: function(event) {
-    return this.checkEvent(event) && this.events[event].length > 0;
-  },
-
-  /**
-  * Add a listener to the end of the listeners array for the specified event.
-  * @param {String} event
-  * @param {Function} listener
-  */
-  on: function(event, listener, bindTarget) {
-    if (listener === undefined) {
-      return this;
-    } else if (typeof listener !== 'function') {
-      this.logger.error('listener must be a function');
-      return this;
-    } else if (!this.checkEvent(event)) {
-      this.logger.error('unable to add a listener to a nonexistent event '+ event);
-      throw new TypeError('Invalid or uninitialized event: ' + event);
-    }
-
-    var listenerObj = { listener: listener };
-    if (bindTarget) {
-      listenerObj.bindTarget = bindTarget;
-    }
-
-    if (this.events[event].length >= this.maxListeners) {
-      this.logger.warn('max listeners exceeded for event '+ event);
-      return this;
-    }
-
-    this.events[event].push(listenerObj);
-    this.logger.log('new listener added to event '+ event);
-    return this;
-  },
-
-  /**
-  * Add a one time listener for the specified event.
-  * The listener is invoked only the next time the event is fired, then it is removed.
-  * @param {String} event
-  * @param {Function} listener
-  */
-  once: function(event, listener, bindTarget) {
-    var self = this;
-    function listenOnce () {
-      /* jshint validthis:true */
-      listener.apply(this, arguments);
-      self.off(event, listenOnce, bindTarget);
-    }
-
-    return this.on(event, listenOnce, bindTarget);
-  },
-
-  /**
-  * Remove a listener from the listener array for the specified event.
-  * Note that the order of the array elements will change after removing the listener
-  * @param {String} event
-  * @param {Function} listener
-  */
-  off: function(event, listener, bindTarget) {
-    var events, length,
-      idx = 0;
-
-    if (listener && typeof listener !== 'function') {
-      this.logger.error('listener must be a function');
-      return this;
-    } else if (!event) {
-      for (idx in this.events) {
-        this.events[idx] = [];
-      }
-      return this;
-    } else if (!this.checkEvent(event)) {
-      this.logger.error('unable to remove a listener from a nonexistent event '+ event);
-      throw new TypeError('Invalid or uninitialized event: ' + event);
-    }
-
-    events = this.events[event];
-    length = events.length;
-
-    while (idx < length) {
-      if (events[idx] &&
-          (!listener || events[idx].listener === listener) &&
-          (!bindTarget || events[idx].bindTarget === bindTarget)) {
-        events.splice(idx,1);
-      } else {
-        idx ++;
-      }
-    }
-
-    return this;
-  },
-
-  /**
-  * By default EventEmitter will print a warning
-  * if more than C.MAX_LISTENERS listeners are added for a particular event.
-  * This function allows that limit to be modified.
-  * @param {Number} listeners
-  */
-  setMaxListeners: function(listeners) {
-    if (typeof listeners !== 'number' || listeners < 0) {
-      this.logger.error('listeners must be a positive number');
-      return this;
-    }
-
-    this.maxListeners = listeners;
-    return this;
-  },
-
-  /**
-  * Execute each of the listeners in order with the supplied arguments.
-  * @param {String} events
-  * @param {Array} args
-  */
-  emit: function(event) {
-    if (!this.checkEvent(event)) {
-      this.logger.error('unable to emit a nonexistent event '+ event);
-      throw new TypeError('Invalid or uninitialized event: ' + event);
-    }
-
-    this.logger.log('emitting event '+ event);
-
-    // Fire event listeners
-    var args = Array.prototype.slice.call(arguments, 1);
-    this.events[event].slice().forEach(function (listener) {
-      try {
-        listener.listener.apply(listener.bindTarget || this, args);
-      } catch(err) {
-        this.logger.error(err.stack);
-      }
-    }, this);
-
-    return this;
+EventEmitter.prototype.off = function off (eventName, listener) {
+  if (arguments.length < 2) {
+    return this.removeAllListeners.apply(this, arguments);
+  } else {
+    return this.removeListener(eventName, listener);
   }
 };
 
-EventEmitter.C = C;
-
-SIP.EventEmitter = EventEmitter;
-};
+module.exports = EventEmitter;

src/RegisterContext.js

@@ -5,11 +5,7 @@ var RegisterContext;
 
 RegisterContext = function (ua) {
   var params = {},
-      regId = 1,
-      events = [
-        'registered',
-        'unregistered'
-      ];
+      regId = 1;
 
   this.registrar = ua.configuration.registrarServer;
   this.expires = ua.configuration.registerExpires;
@@ -43,7 +39,6 @@ RegisterContext = function (ua) {
   this.registered = false;
 
   this.logger = ua.getLogger('sip.registercontext');
-  this.initMoreEvents(events);
 };
 
 RegisterContext.prototype = {

src/SIP.js

@@ -20,7 +20,7 @@ Object.defineProperties(SIP, {
 
 require('./Utils')(SIP, environment);
 SIP.LoggerFactory = require('./LoggerFactory')(environment.console);
-require('./EventEmitter')(SIP);
+SIP.EventEmitter = require('./EventEmitter');
 SIP.C = require('./Constants')(SIP.name, SIP.version);
 SIP.Exceptions = require('./Exceptions');
 SIP.Timers = require('./Timers')(environment.timers);

src/ServerContext.js

@@ -3,12 +3,6 @@ module.exports = function (SIP) {
 var ServerContext;
 
 ServerContext = function (ua, request) {
-  var events = [
-      'progress',
-      'accepted',
-      'rejected',
-      'failed'
-    ];
   this.ua = ua;
   this.logger = ua.getLogger('sip.servercontext');
   this.request = request;
@@ -30,8 +24,6 @@ ServerContext = function (ua, request) {
 
   this.localIdentity = request.to;
   this.remoteIdentity = request.from;
-
-  this.initEvents(events);
 };
 
 ServerContext.prototype = new SIP.EventEmitter();