var backButton = {
	event: { hash: '', refer: '', type: 'load'},
	copyHistory: [],
/* - */
	addEvent: function(type,fn){
		if(type == 'backbutton' && (!this.events || !this.events.backbutton))
					this.addEvent('domready',backButton.start.bind(backButton));
		return this._addEvent(type,fn);
	},
/* - */
	getHash: function() {
		return location.hash.substring(1);
	},
/* - */
	start: function() {
		window.hash = this.hash.bind(this);
	    if(window.ie) this.onHash = this.onIframe;
	    if(window.khtml) {
			this.history = $A(history).slice(1);
			this.history.push(this.getHash());
			this.oldHistoryLength = location.hash ? -1 : history.length;
			this.onHash = this.onLink;
	    }
		this.timer = this.onHash.periodical(1000,this,[false]);
	},
/* - */
	onHash: function(force) {
		var hash = this.getHash();
		if(hash=='' || hash.substring(0,4) == 'http'){
			if(hash != this.event.hash || force) this.fireEvent(hash);
		}
	},
/* - */
	onLink: function(force) {
		var h = history.length;
	    if (h != this.oldHistoryLength || force) {
			if(typeof (this.history[h-1]) == 'undefined') this.history = this.copyHistory.copy();
			this.fireEvent(this.history[h-1]);
			this.oldHistoryLength = h;
	    }
	},
/* - */
	onIframe: function() {
		$clear(this.timer);
		this.iframe = new Element('iframe').setStyle('display','none').injectInside(document.body).contentWindow.document;
		if(this.getHash()) this.updateIFrame(this.getHash());
	},
/* - */
	updateIFrame: function(hash) {
	    this.iframe.open();
	    this.iframe.write('<script>parent.location.hash = "'+hash+'"; parent.backButton.fireEvent("'+hash +'");</script>');
	    this.iframe.close();
  },
/* - */
	hash: function(hash) {
		if($type(hash) != 'string') return this.event.hash;
	    this.event.type = 'click';
        if(!window.ie) {
			if(window.khtml) {
		      	var link = new Element('a').setProperty('href','#'+hash), event = document.createEvent('MouseEvents');
		      	event.initEvent('click', true, true);
		      	link.dispatchEvent(event);
		      	if(this.history.length >= history.length) {
		        	this.copyHistory = this.history.copy();
		        	this.history = this.history.splice(0, history.length-1);
		      	}
		      	this.history.push(hash);
			} else location.hash = hash || '#';
			this.onHash(true);
		} else this.updateIFrame(hash);
	},
/* - */	
	fireEvent: function(vhash) {
		var vrefer = this.event.hash;
		this.event.hash = vhash;
		Element.prototype.fireEvent.call(window, 'backbutton', [Object.extend({},this.event)]);
		Object.extend(this.event,{ refer: vrefer, type: 'backbutton' });
	}
};
/*
 * 
  */
window.extend({
	_addEvent: window.addEvent,
	addEvent: backButton.addEvent,
	hash: Class.empty
});