var XMLHandler = function ()
{
	this.DOMDocument = null;
}

/**
 * Return a XMLHttpRequest Handler.
 * Currently works for both IE and Gecko.
 * Maybe add support for Opera?
 * 
 * @see http://www.scss.com.au/scripts/xmlhttprequest.js
 */
XMLHandler.prototype.GetHttpRequest = function ()
{
	if (window.XMLHttpRequest) {
		return new XMLHttpRequest();
	} else if (window.ActiveXObject) {
		var aMSXML = new Array(
			'Msxml2.XMLHTTP.5.0',
			'Msxml2.XMLHTTP.4.0',
			'Msxml2.XMLHTTP.3.0',
			'Msxml2.XMLHTTP',
			'Microsoft.XMLHTTP');
		
		for (var i = 0; i < aMSXML.length; i++) {
			try {
				return new ActiveXObject(aMSXML[i]);
			} catch (e) {}
		}
		
		return null;
	}
}

/**
 * Load a specific URL into this XMLHandler.
 * If asyncFunction is specified, this function will return immediately
 * and the asyncFunction will be called when the document has been
 * fetched.
 */
XMLHandler.prototype.LoadURL = function (xmlUrl, asyncFunction, silentRequest)
{
	var bAsync = (typeof(asyncFunction) == 'function');
	var oXmlHttp = this.GetHttpRequest();
	
	oXmlHttp.open('GET', xmlUrl, bAsync);
	
	if (bAsync) {
		var oXmlHandler = this;
		oXmlHttp.onreadystatechange = function ()
		{
			if (oXmlHttp.readyState == 4) {
				if (oXmlHttp.status == 200) {
					if (oXmlHttp.responseXML != null) {
						oXmlHandler.DOMDocument = oXmlHttp.responseXML;
						asyncFunction(oXmlHandler);
					} else {
						if (!silentRequest && confirm('XML Response Error.\nView response?')) {
							alert('-= REQUEST =-\n' + xmlUrl + '\n\n-= RESPONSE =-\n' + oXmlHttp.responseText);
						}
					}
				} else if (!silentRequest) {
					alert('XML Request Error: (' + oXmlHttp.status + ') ' + oXmlHttp.statusText);
				}
			}
		}
	}
	
	try {
		oXmlHttp.send(null);
		
		if (!bAsync) {
			if (oXmlHttp.status == 200) {
				if (oXmlHttp.responseXML != null) {
					this.DOMDocument = oXmlHttp.responseXML;
				} else {
					if (!silentRequest && confirm('XML Response Error.\nView response?')) {
						alert('-= REQUEST =-\n' + xmlUrl + '\n\n-= RESPONSE =-\n' + oXmlHttp.responseText);
					}
					
					return false;
				}
			} else {
				if (!silentRequest) {
					alert('XML Request Error: (' + oXmlHttp.status + ') ' + oXmlHttp.statusText);
				}
				
				return false;
			}
		}
	} catch (e) {
		if (!silentRequest) {
			alert('XML Request Error: Unable to connect.');
		}
		
		return false;
	}
	
	return true;
}

/**
 * Select nodes in the fetched XML document according to the specified
 * xpath. The nodes are returned as an array.
 */
XMLHandler.prototype.SelectNodes = function (xpath)
{
	try {
		return this.DOMDocument.selectNodes(xpath);
	} catch (e) {}
	
	var aNodes = new Array();
	
	var xPathResult = this.DOMDocument.evaluate(xpath, this.DOMDocument,
			this.DOMDocument.createNSResolver(this.DOMDocument.documentElement),
			XPathResult.ORDERED_NODE_ITERATOR_TYPE, null);
	
	if (xPathResult) {
		var oNode;
		while (oNode = xPathResult.iterateNext()) {
			aNodes[aNodes.length] = oNode;
		}
	}
	
	return aNodes;
}

/**
 * Select the first node in the XML document according to the specified
 * xpath.
 */
XMLHandler.prototype.SelectNode = function (xpath)
{
	try {
		return this.DOMDocument.selectSingleNode(xpath);
	} catch (e) {}
	
	var xPathResult = this.DOMDocument.evaluate(xpath, this.DOMDocument,
			this.DOMDocument.createNSResolver(this.DOMDocument.documentElement),
			XPathResult.FIRST_ORDERED_NODE_TYPE, null);
	
	if (xPathResult && xPathResult.singleNodeValue) {
		return xPathResult.singleNodeValue;
	}
	
	return null;
}