var XHR = new Class({

	options: {
		method: 'post',
		async: true,
		onRequest: Class.empty,
		onSuccess: Class.empty,
		onFailure: Class.empty,
		urlEncoded: true,
		encoding: 'utf-8',
		autoCancel: false,
		headers: {}
	},

	setTransport: function(){
		this.transport = (window.XMLHttpRequest) ? new XMLHttpRequest() : (window.ie ? new ActiveXObject('Microsoft.XMLHTTP') : false);
		return this;
	},

	initialize: function(options){
		this.setTransport().setOptions(options);
		this.options.isSuccess = this.options.isSuccess || this.isSuccess;
		this.headers = {};
		if (this.options.urlEncoded && this.options.method == 'post'){
			var encoding = (this.options.encoding) ? '; charset=' + this.options.encoding : '';
			this.setHeader('Content-type', 'application/x-www-form-urlencoded' + encoding);
		}
		if (this.options.initialize) this.options.initialize.call(this);
	},

	onStateChange: function(){
		if (this.transport.readyState != 4 || !this.running) return;
		this.running = false;
		var status = 0;
		try {status = this.transport.status;} catch(e){};
		if (this.options.isSuccess.call(this, status)) this.onSuccess();
		else this.onFailure();
		this.transport.onreadystatechange = Class.empty;
	},

	isSuccess: function(status){
		return ((status >= 200) && (status < 300));
	},

	onSuccess: function(){
		this.response = {
			'text': this.transport.responseText,
			'xml': this.transport.responseXML
		};
		this.fireEvent('onSuccess', [this.response.text, this.response.xml]);
		this.callChain();
	},

	onFailure: function(){
		this.fireEvent('onFailure', this.transport);
	},

	setHeader: function(name, value){
		this.headers[name] = value;
		return this;
	},

	send: function(url, data){
		if (this.options.autoCancel) this.cancel();
		else if (this.running) return this;
		this.running = true;
		if (data && this.options.method == 'get'){
			url = url + (url.contains('?') ? '&' : '?') + data;
			data = null;
		}
		this.transport.open(this.options.method.toUpperCase(), url, this.options.async);
		this.transport.onreadystatechange = this.onStateChange.bind(this);
		if ((this.options.method == 'post') && this.transport.overrideMimeType) this.setHeader('Connection', 'close');
		$extend(this.headers, this.options.headers);
		for (var type in this.headers) try {this.transport.setRequestHeader(type, this.headers[type]);} catch(e){};
		this.fireEvent('onRequest');
		this.transport.send($pick(data, null));
		return this;
	},

	cancel: function(){
		if (!this.running) return this;
		this.running = false;
		this.transport.abort();
		this.transport.onreadystatechange = Class.empty;
		this.setTransport();
		this.fireEvent('onCancel');
		return this;
	}

});

XHR.implement(new Chain, new Events, new Options);

var Ajax = XHR.extend({

	options: {
		data: null,
		update: null,
		onComplete: Class.empty,
		evalScripts: false,
		evalResponse: false
	},

	initialize: function(url, options){
		this.addEvent('onSuccess', this.onComplete);
		this.setOptions(options);
		this.options.data = this.options.data || this.options.postBody;
		if (!['post', 'get'].contains(this.options.method)){
			this._method = '_method=' + this.options.method;
			this.options.method = 'post';
		}
		this.parent();
		this.setHeader('X-Requested-With', 'XMLHttpRequest');
		this.setHeader('Accept', 'text/javascript, text/html, application/xml, text/xml, */*');
		this.url = url;
	},

	onComplete: function(){
		if (this.options.update) $(this.options.update).empty().setHTML(this.response.text);
		if (this.options.evalScripts || this.options.evalResponse) this.evalScripts();
		this.fireEvent('onComplete', [this.response.text, this.response.xml], 20);
	},

	request: function(data){
		data = data || this.options.data;
		switch($type(data)){
			case 'element': data = $(data).toQueryString(); break;
			case 'object': data = Object.toQueryString(data);
		}
		if (this._method) data = (data) ? [this._method, data].join('&') : this._method;
		return this.send(this.url, data);
	},

	evalScripts: function(){
		var script, scripts;
		if (this.options.evalResponse || (/(ecma|java)script/).test(this.getHeader('Content-type'))) scripts = this.response.text;
		else {
			scripts = [];
			var regexp = /<script[^>]*>([\s\S]*?)<\/script>/gi;
			while ((script = regexp.exec(this.response.text))) scripts.push(script[1]);
			scripts = scripts.join('\n');
		}
		if (scripts) (window.execScript) ? window.execScript(scripts) : window.setTimeout(scripts, 0);
	},

	getHeader: function(name){
		try {return this.transport.getResponseHeader(name);} catch(e){};
		return null;
	}

});

Object.toQueryString = function(source){
	var queryString = [];
	for (var property in source) queryString.push(encodeURIComponent(property) + '=' + encodeURIComponent(source[property]));
	return queryString.join('&');
};

Element.extend({

	send: function(options){
		return new Ajax(this.getProperty('action'), $merge({data: this.toQueryString()}, options, {method: 'post'})).request();
	}

});