// written by Dean Edwards, 2005
// with input from Tino Zijdel, Matthias Miller, Diego Perini

// http://dean.edwards.name/weblog/2005/10/add-event/

function addEvent(element, type, handler) {
	// Check if the element exists
	if ( element ) {
		if (element.addEventListener) {
			element.addEventListener(type, handler, false);
		} else {
			// assign each event handler a unique ID
			if (!handler.$$guid) handler.$$guid = addEvent.guid++;
			// create a hash table of event types for the element
			if (!element.events) element.events = {};
			// create a hash table of event handlers for each element/event pair
			var handlers = element.events[type];
			if (!handlers) {
				handlers = element.events[type] = {};
				// store the existing event handler (if there is one)
				if (element["on" + type]) {
					handlers[0] = element["on" + type];
				}
			}
			// store the event handler in the hash table
			handlers[handler.$$guid] = handler;
			// assign a global event handler to do all the work
			element["on" + type] = handleEvent;
		}
	}
};
// a counter used to create unique IDs
addEvent.guid = 1;

function removeEvent(element, type, handler) {
	if ( element ) {
		if (element.removeEventListener) {
			element.removeEventListener(type, handler, false);
		} else {
			// delete the event handler from the hash table
			if (element.events && element.events[type]) {
				delete element.events[type][handler.$$guid];
			}
		}
	}
};

function handleEvent(event) {
	var returnValue = true;
	// grab the event object (IE uses a global event object)
	event = event || fixEvent(((this.ownerDocument || this.document || this).parentWindow || window).event);
	// get a reference to the hash table of event handlers
	var handlers = this.events[event.type];
	// execute each event handler
	for (var i in handlers) {
		this.$$handleEvent = handlers[i];
		if (this.$$handleEvent(event) === false) {
			returnValue = false;
		}
	}
	return returnValue;
};

function fixEvent(event) {
	// add W3C standard event methods
	event.preventDefault = fixEvent.preventDefault;
	event.stopPropagation = fixEvent.stopPropagation;
	return event;
};
fixEvent.preventDefault = function() {
	this.returnValue = false;
};
fixEvent.stopPropagation = function() {
	this.cancelBubble = true;
};