var requests = new Array();

function CreateXMLHttpRequest()
{
	var	xmlHttpReq = null;
	if( typeof(XMLHttpRequest)!="undefined" )
		xmlHttpReq = new XMLHttpRequest();
	if( xmlHttpReq != null ) return xmlHttpReq;
	try	
	{
		xmlHttpReq = new ActiveXObject("Msxml2.XMLHTTP");
	} 
	catch(e) 
	{
		try
		{
			xmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");
		} 
		catch(oc)	
		{
			return null;
		}
	}
	return xmlHttpReq;
}

function ajax_create_request(context)
{
	for(var i=0; i<requests.length; i++)
	{
		if(requests[i].readyState == 4)
		{
			requests[i].abort();
			requests[i].context = context;
			return requests[i];
		}
	}

	var pos = requests.length;
	
	requests[pos] = Object();
	requests[pos].obj = CreateXMLHttpRequest();
	requests[pos].context = context;
	
	return requests[pos];
}


function ajax_request(url, data, callback, context)
{
	var request = ajax_create_request(context);
	var async = typeof(callback) == 'function';

	if(async) request.obj.onreadystatechange = function()
	{
		if(request.obj.readyState == 4)
			callback(new ajax_response(request));
	}
	
	request.obj.open('GET', url, async);
	request.obj.send(data);
	
	if(!async)
		return new ajax_response(request);
}

function ajax_request_with_params_for_callback(url, data, callback, context, params)
{
	var request = ajax_create_request(context);
	var async = typeof(callback) == 'function';

	if(async) request.obj.onreadystatechange = function()
	{
		if(request.obj.readyState == 4)
			callback(new ajax_response(request), params);
	}
	
	request.obj.open('GET', url, async);
	request.obj.send(data);
	
	if(!async)
		return new ajax_response(request);
}

function ajax_response(request)
{
	this.request = request.obj;
	this.error = null;
	this.value = null;
	this.context = request.context;
	
	if(request.obj.status == 200)
	{
		try
		{			
			// For now just assign the responseText
			// For JSON use: this.value = object_from_json(request); 
			this.value = request.obj.responseText;
			if(this.value && this.value.error)
			{
				this.error = this.value.error;
				this.value = null;
			}
		}
		catch(e)
		{
			this.error = new ajax_error(e.name, e.description, e.number);
		}
	}
	else
	{
		this.error = new ajax_error('HTTP request failed with status: ' + request.obj.status, request.obj.status);
	}
	
	return this;
}


ajax_error.prototype.toString = function()
{
	return this.name + " " + this.description;
}


function ajax_error(name, description, number)
{
	this.name = name;
	this.description = description;
	this.number = number;

	return this;
}


//******************************************************
// The following code is to be used for JSON (JavaScript 
// Object Notation) implementation
//******************************************************

//function enc(s)
//{
//	return s == null ? null : s.toString().replace(/\%/g, "%26").replace(/=/g, "%3D");
//}

//function object_from_json(request)
//{
//	if(request.obj.responseXML != null && request.obj.responseXML.xml != null && request.obj.responseXML.xml != '')
//		return request.obj.responseXML;
//	
//	var r = null;	
//	eval('r=' + request.obj.responseText + ';');
//	return r;
//}


//function json_from_object(o)
//{
//	if(o == null)
//		return 'null';

//	switch(typeof(o))
//	{
//		case 'object':
//			if(o.constructor == Array)		// checks if it is an array [,,,]
//			{
//				var s = '';
//				for(var i=0; i<o.length; ++i)
//				{
//					s += json_from_object(o[i]);
//
//					if(i < o.length -1)
//						s += ',';
//				}
//
//				return '[' + s + ']';
//			}
//			break;
//		case 'string':
//			return '"' + o.replace(/(["\\])/g, '\\$1') + '"';
//		default:
//			return String(o);
//	}
//}