EventDispatcher

/*
    CASA Framework for ActionScript 2.0
    Copyright (C) 2006  CASA Framework
    http://casaframework.org
    
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.
    
    This library 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
    Lesser General Public License for more details.
    
    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
*/

import org.casaframework.core.CoreObject;
import org.casaframework.event.DispatchableInterface;
import org.casaframework.util.TypeUtil;

/**
    Provides event notification and listener management capabilities to objects. 
    
    Advantages of using this EventDispatcher:
    <ul>
        <li>Ability to {@link #addEventObserver remap event handlers} to a function not sharing the same name as the event.</li>
        <li>Ability to {@link #removeEventObserversForEvent remove all} event observers for a specified event.</li>
        <li>Ability to {@link #removeEventObserversForScope remove all} event observers for a specified scope.</li>
        <li>Ability to {@link #removeAllEventObservers remove all} event observers subscribed to broadcasting object.</li>
    </ul>

    @author Aaron Clinger
    @version 12/18/06
    @usageNote <strong>Always call {@link #destroy} before deleting/removing an EventDispatcher instance.</strong>
*/

class org.casaframework.event.EventDispatcher extends CoreObject implements DispatchableInterface {
    private var $eventMap:Object;
    
    public function EventDispatcher() {
        super();
        
        this.$eventMap = new Object();
        
        this.$setClassDescription('org.casaframework.event.EventDispatcher');
    }
    
    public function addEventObserver(scope:Object, eventName:String, eventHandler:String):Boolean {
        var eventFunction:String = (eventHandler == undefined) ? eventName : eventHandler;
        
        if (!TypeUtil.isTypeOf(scope[eventFunction], 'function'))
            return false;
        
        var eventList:Array = this.$eventMap[eventName];
        
        if (eventList == undefined)
            this.$eventMap[eventName] = new Array();
        else {
            var len:Number = eventList.length;
            while (len--)
                if (eventList[len].obser == scope && eventList[len].funct == eventFunction)
                    return false;
        }
        
        var event:Object = new Object();
        event.obser      = scope;
        event.funct      = eventFunction;
        
        this.$eventMap[eventName].push(event);
        
        return true;
    }
    
    public function removeEventObserver(scope:Object, eventName:String, eventHandler:String):Boolean {
        var funct:String    = (eventHandler == undefined) ? eventName : eventHandler;
        var eventList:Array = this.$eventMap[eventName];
        var len:Number      = eventList.length;
        
        while (len--) {
            if (eventList[len].obser == scope && eventList[len].funct == funct) {
                eventList.splice(len, 1);
                
                if (eventList.length == 0)
                    delete this.$eventMap[eventName];
                
                return true;
            }
        }
        
        return false;
    }
    
    public function removeEventObserversForEvent(eventName:String):Boolean {
        if (this.$eventMap[eventName] == undefined)
            return false;
        
        delete this.$eventMap[eventName];
        
        return true;
    }
    
    public function removeEventObserversForScope(scope:Object):Boolean {
        var removed:Boolean = false;
        
        for (var i:String in this.$eventMap) {
            var eventList:Array = this.$eventMap[i];
            var len:Number      = eventList.length;
            
            while (len--) {
                if (eventList[len].obser == scope) {
                    this.$eventMap[i].splice(len, 1);
                    
                    if (eventList.length == 0)
                        delete this.$eventMap[i];
                    
                    removed = true;
                }
            }
        }
        
        return removed;
    }
    
    public function removeAllEventObservers():Boolean {
        for (var i:String in this.$eventMap) {
            this.$eventMap[i].splice(0);
            delete this.$eventMap[i];
        }
        
        this.$eventMap = new Object();
        
        return true;
    }
    
    public function dispatchEvent(eventName:String):Boolean {
        var eventList:Array = this.$eventMap[eventName];
        if (eventList == undefined)
            return false;
        
        var i:Number = -1;
        while (++i < eventList.length)
            eventList[i].obser[eventList[i].funct].apply(eventList[i].obser, arguments.slice(1));
        
        return true;
    }
    
    public function destroy():Void {
        this.removeAllEventObservers();
        delete this.$eventMap;
        
        super.destroy();
    }
}