var Core = {};

if (document.addEventListener) 
{
	Core.addEventListener = function(target, type, listener)
	{
		target.addEventListener(type, listener, false);
	};
	
	Core.removeEventListener = function(target, type, listener)
	{
		target.removeEventListener(type, listener, false);
	};
	
	Core.preventDefault = function(e)
	{
		e.preventDefault();
	};
	
	Core.stopPropogation = function(e)
	{
		e.stopPropogation();
	};
}
else if (document.attachEvent) 
{
	Core.addEventListener = function(target, type, listener)
	{
		if (Core._findListener(target, type, listener) != -1) { return; };
		
		var listener2 = function()
		{
			var event = window.event;
			
			if (Function.prototype.call) 
			{
				listener.call(target, event);
			}
			else
			{
				target._currentListener = listener;
				target._currentListener(event);
				target._currentListener = null;
			}
		};
		
		target.attachEvent('on' + type, listener2);
		
		var listenerRecord = 
		{
			target: target,
			type: type,
			listener: listener,
			listener2: listener2
		};
		
		var targetDocument = target.document || target;
		var targetWindow = targetDocument.parentWindow;
		
		var listenerId = 'l' + Core._listenerCounter++;
		
		if (!targetWindow._allListenerts) 
		{
			targetWindow._allListeners = {};
		}
		else
		{
			targetWindow._allListeners[listenerId] = listenerRecord;
		}
		
		if (!target._listeners) 
		{
			target._listeners = {};
		}
		else
		{
			target._listeners[target._listeners.length] = listenerId;
		}
		
		if (!targetWindow._unloadListenerAdded) 
		{
			targetWindow._unloadListenerAdded = true;
			targetWindow.attachEvent('onunload', Core._removeAllListeners);
		}
	};
	
	Core.removeEventListener = function(target, type, listener)
	{
		var listenerIndex = Core._findListener(target, type, listener);
		if (listenerIndex == -1) { return; };
		
		var targetDocument = target.document || target;
		var targetWindow = targetDocument.parentWindow;
		
		var listenerId = target._listeners[listenerIndex];
		var listenerRecord = targetWindow._allListeners[listenerId];
		
		target.detachEvent('on' + type, listenerRecord.listener2);
		target._listeners.splice(listenerIndex, 1);
		
		delete targetWindow._allListeners[listenerId];
	};
	
	Core.preventDefault = function(e)
	{
		e.returnValue = false;
	};
	
	Core.stopPropogation = function(e)
	{
		e.cancelBubble = true;
	};
	
	Core._findListener = function(target, type, listener)
	{
		var listeners = target._listeners;
		if (!listeners) { return -1; };
		
		var targetDocument = target.document || target;
		var targetWindow = targetDocument.parentWindow;
		
		for (var i = listeners.length - 1; i >= 0; i--) 
		{
			var listenerId = listeners[i];
			
			var listenerRecord = targetWindow._allListeners[listenerId];
			
			if (listenerRecord.type == type && listenerRecord.listener == listener) { return i; };
		}
		return -1;
	};
	
	Core._removeAllListeners = function()
	{
		var targetWindow = this;
		
		for(id in targetWindow._allListeners)
		{
			var listenerRecord = targetWindow._allLIsteners[id];
			listenerRecord.target.detachEvent('on' + listenerRecord.type, listenerRecord.listener2);
			delete targetWindow._allListeners[id];
		}
	};
	
	Core._listenerCounter = 0;
};

Core.addClass = function(target, theClass)
{
	if (!Core.hasClass(target, theClass)) 
	{
		if (target.className == '') 
		{
			target.className = theClass;
		}
		else
		{
			target.className += ' ' + theClass;
		}
	}
};

Core.getElementsByClass = function(theClass, node, tag)
{
	var elementArray = [];
	
	if (node == null) {
		node = document;
	}
	
	if (tag == null) 
	{
		tag = '*';
	}
	
	//removed from original and refactored
	elementArray = node.getElementsByTagName(tag);
	
	var matchedArray = [];
	var pattern = new RegExp("(^| )" + theClass + "( |$)");
	
	for (var i=0; i < elementArray.length; i++) {
		if (pattern.test(elementArray[i].className)) 
		{
			// can we just use array.push?
			matchedArray[matchedArray.length] = elementArray[i];
		}
	}
	return matchedArray;
};

Core.getElementsByRel = function(theRel)
{
	var elementArray = [];
	
	elementArray = document.getElementsByTagName('a');
	
	var matchedArray = [];
	var pattern = new RegExp("(^| )" + theRel + "( |$)");
	
	for (var i=0; i < elementArray.length; i++) {
		if (pattern.test(elementArray[i].rel)) 
		{
			matchedArray[matchedArray.length] = elementArray[i];
		}
	}
	return matchedArray;
};

Core.hasClass = function(target, theClass)
{
	//extract into regex function
	var pattern = new RegExp("(^| )" + theClass + "( |$)");
	
	if (pattern.test(target.className)) 
	{
		return true;
	}
	return false;
};

Core.removeClass = function(target, theClass)
{
	var pattern = new RegExp("(^| )" + theClass + "( |$)");
	
	target.className = target.className.replace(pattern, "$1");
	target.className = target.className.replace(/ $/, '');
};

Core.getComputedStyle = function(element, styleProperty)
{
	var computedStyle = null;
	
	if (typeof element.currentStyle != 'undefined') 
	{
		computedStyle = element.currentStyle;
	}
	else
	{
		computedStyle = document.defaultView.getComputedStyle(element, null);
	}
	return computedStyle[styleProperty];
};

//to do - add commonly used regexs used (email, classname, relname)

Core.start = function(runnable)
{
	Core.addEventListener(window, 'load', runnable.init);
}