/**
 * @author 		Matthew Foster
 * @date		June 6th 2007
 * @purpose		To have a base class to extend subclasses from to inherit event dispatching functionality.
 * @procedure	Use a hash of event "types" that will contain an array of functions to execute.  The logic is if any function explicitally returns false the chain will halt execution.
 */
 var EventDispatcher = function(){};
     
     
     Object.extend(EventDispatcher.prototype,
                         {
                              
                              buildListenerChain : function(){
                                   
                                   if(!this.listenerChain)
                                        this.listenerChain = {};                                   
                              
                              },
                              addEventListener : function(type, listener){
                                   
                                   if(!listener instanceof Function)
                                        throw { message : "Listener isn't a function" };
                                   
                                   this.buildListenerChain();
                                   
                                   
                                   
                                   if(!this.listenerChain[type])                         
                                        this.listenerChain[type] = [listener];
                                   else
                                        this.listenerChain[type].push(listener);
                                   
                              },
                              hasEventListener : function(type){
                                   
                                   return (typeof this.listenerChain[type] != "undefined");
                              
                              },
                              removeEventListener : function(type, listener){
                                   if(!this.hasEventListener(type))
                                        return false;
                                        
                                   for(var i = 0; i < this.listenerChain[type].length; i++)
                                        if(this.listenerChain[type][i] == listener)
                                             this.listenerChain.splice(i, 1);
                              
                              },
                              dispatchEvent : function(type, args){
                                   this.buildListenerChain();
                                   
                                   if(!this.hasEventListener(type))
                                        return false;
                                        
                                   this.listenerChain[type].any(function(f){ return (f(args) == false ? true : false); });
                              
                              }
                         }
                         
                    );