/**
 * Create loader to request data from server
 *
 * @param handler Object providing clear()/render() function when data arrives
 */
function it_loader(handler)
{
	/* Clear cache etc. if completely new data */
	this.loader = null;
	this.handler = handler;
	this.instance = it_loader.instances++;
	this.callid = 0;
	this.clear();
}

/* Methods */
it_loader.prototype =
{

/* Clear cache and initialize handler */
clear: function()
{
	/* Clear cache etc. if completely new data */
	this.entry = new Array();
	this.start = this.end = 0;
	this.attr = { num: 0, loadtime: 0 };
	this.method = "GET";
	this.post_data = null;

	if (this.handler.clear)
		this.handler.clear();
},

load: function(baseurl, pos, num, query_volatile, retry)
{
	/* Convert to int */
	pos -= 0;
	num -= 0;

	if (isNaN(retry))
		retry = 0;

	if (baseurl != this.baseurl)
	{
		this.clear();
		this.baseurl = baseurl;
		this.start = this.end = pos;
	}

	this.pos = pos;
	this.num = num;
	this.query_volatile = query_volatile;

	if (this.loader)
		this.stop();

	while ((num > 0) && this.entry[pos])
	{
		pos++;
		num--;
	}

	if (this.attr.eof)
		num = Math.min(num, this.end - pos);

	if (num > 0)
	{
		this.loader = null;

		if (retry)
			baseurl += "&retry=" + retry;

		// use XMLHTTP request if available
		if (baseurl.indexOf('http://') < 0 || baseurl.indexOf(window.location.hostname) > 0)
		{
			try
			{
				this.loader = new XMLHttpRequest();
			}
			catch (e)
			{
				var classnames = [ 'MSXML2.XMLHTTP', 'Microsoft.XMLHTTP' ];

				for (var i in classnames)
				{
					try
					{
						this.loader = new ActiveXObject(classnames[i]);
						break;
					}
					catch (e) { }
				}
			}

			try
			{
				this.loader.open(this.method, baseurl + "&pos=" + pos + "&num=" + num + (query_volatile ? query_volatile : ""));
				var me = this;
				this.loader.onreadystatechange = function() { me.readyStateChanged(); }
				var workingxmlhttp = this.loader.onreadystatechange;

				if (!workingxmlhttp)    /* Old Konqueror */
					this.loader = null;
			}
			catch (e) { }
		}

		if (this.loader)
		{
			if (this.method == "POST")
				this.loader.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");

			this.starttime = new Date().getTime();
			this.retry = retry;
			this.loader.send(this.post_data);
		}
		else
		{
			var req_url = baseurl + "&pos=" + pos + "&num=" + num + (query_volatile ? query_volatile : "") + (this.post_data ? '&' + this.post_data : "") + "&itjs_call=it_loader.__inst" + this.instance + "&itjs_callid=" + ++this.callid;

			if (window.opera && !window.XMLHttpRequest)  // Opera 7 only works with iframes
			{
				this.scrpt = document.createElement("iframe");
				this.scrpt.style.width = this.scrpt.style.height = 1;
				req_url += "&itjs_iframe=1";
			}
			else
				this.scrpt = document.createElement("script");

			it_loader['__inst'+this.instance] = this;
			this.loader = { starttime: new Date().getTime(), retry: retry };
			try
			{
				this.scrpt.src = req_url;
				document.body.appendChild(this.scrpt);
			}
			catch (e) { return false; }
		}
	}
	else
		this.handler.render(this);

	return true;
},

post: function(baseurl, data)
{
	this.clear();
	this.method = "POST";
	this.baseurl = baseurl;
	this.start = this.end = 10;
	this.post_data = "";

	if (typeof data == 'object')
	{
		for (var k in data)
			this.post_data += (this.post_data ? "&" : "") + k + "=" + escape(data[k]);
	}
	else
		this.post_data = data;

	this.load(baseurl, 0, 1, "");
},

readyStateChanged: function()
{
	var loader = this.loader;	// Avoid race conditions

	if (loader && (loader.readyState == 4))
	{
		var data = null;

		try
		{
			if (loader.responseText != "")
				data = eval("("+ loader.responseText + ")");
		}
		catch (e)
		{
			var retry = this.retry + 1;

			if (retry < 10)
				it_timer({ object: this, method: "retryload", timeout: Math.pow(5, Math.min(retry, 5)), baseurl: this.baseurl, pos: this.pos, num: this.num, query_volatile: this.query_volatile, retry: retry });
			else
				ED(e, loader.responseText);
		}

		if (data)
			this.dataReady(data, this.callid);
	}
},

retryload: function(p)
{
	this.load(p.baseurl, p.pos, p.num, p.query_volatile, p.retry);
},

dataReady: function(data, callid)
{
	var fixkonqueror33gcbug = this.loader;
	var loadtime = new Date().getTime() - this.starttime;

	this.loader = null;

	if ((typeof data == "object") && (this.callid == callid))
	{
		this.attr = { loadtime: loadtime };

		for (var key in data)
		{
			var value = data[key];
			var id = key - 0;

			if (!isNaN(id))
			{
				this.start = Math.min(this.start, id);
				this.end = Math.max(this.end, id + 1);
				this.entry[id] = data[key];
			}
			else
				this.attr[key] = data[key];
		}

		if (this.attr.eof)
			this.attr.num = this.end;	/* Fix bogus # of result value */

		this.handler.render(this);

		if (!this.attr.eof && (this.end < this.pos + this.num))
			this.load(this.baseurl, this.end, this.pos + this.num - this.end);
	}

	this.unlink();
},

stop: function()
{
	try
	{
		this.loader.abort();
	}
	catch (e) { }

	this.unlink();
},

unlink: function()
{
	if (it_loader['__inst'+this.instance])
		it_loader['__inst'+this.instance] = null;

	if (this.loader)
		this.loader = null;

	if (this.scrpt)
	{
		document.body.removeChild(this.scrpt);
		this.scrpt = null;
	}
}/* NO COMMA */

}

// static properties
it_loader.instances = 0;