// singleton class constructor
function Logger() {
	// fields
	this.req;

	// methods
	this.errorToXML = errorToXML;
	this.log = log;
}

// map an error to an XML document
function errorToXML(err) {
	var xml = '<?xml version="1.0"?>' +
        '<JavascriptError xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">' +
        '  <Name>' + encodeXml(err.name) + '</Name>' +
        '  <Message>'  + encodeXml(err.message) + '</Message>';
	if (err.location) xml += '  <Location>' + encodeXml(err.location) + '</Location>';
	xml += '</JavascriptError>';
	return xml;
}

// log method of Logger class
function log(err) {
	// feature sniff
	if (window.XMLHttpRequest) this.req = new XMLHttpRequest();
	else if (window.ActiveXObject) this.req =
		new ActiveXObject("Microsoft.XMLHTTP");
	else return; // throw up our hands in despair
	// set the method and URI
	this.req.open("POST", "/Error/JsError.aspx");
	// set the request headers. REFERER will be the top-level
	// URI which may differ from the location of the error if
	// it occurs in an included .js file
	this.req.setRequestHeader('REFERER', location.href);
	this.req.setRequestHeader('content-type', 'text/xml');
	// function to be called when the request is complete
	this.req.onreadystatechange = errorLogged;
	this.req.send(this.errorToXML(err));
	// if the request doesn't complete in 10 seconds,
	// something is up
	this.timeout = window.setTimeout("abortLog();", 10000);
}

// should only be one instance of the logger
var logger = new Logger();

// we tried, but if there is a connection error, it is hopeless
function abortLog() {
	logger.req.abort();
	alert("Attempt to log the error timed out.");
}

// called when the state of the request changes
function errorLogged() {
	if (logger.req.readyState != 4) return;
	window.clearTimeout(logger.timeout);
	// request completed
	if (logger.req.status >= 400)
		alert('Attempt to log the error failed.');
}

function trapError(msg, URI, ln) {
	// wrap our unknown error condition in an object
	var error = new Error(msg);
	error.location = URI + ', line: ' + ln; // add custom property
	logger.log(error);
	return false;
	//warnUser();
	//return true; // stop the yellow triangle
}

function warnUser() {
	alert("An error has occurred while processing this page.  Our engineers have been alerted!");
	// drastic action
	location.href = '/path/to/error/page.html';
}

function encodeXml(val)
{
    if(val && val.replace)
    {
        var retVal = val.replace(/[&]/g, "&amp;"); //MUST be done FIRST!
        retVal = retVal.replace(/["]/g, "&quot;");
        retVal = retVal.replace(/[']/g, "&apos;");
        retVal = retVal.replace(/[<]/g, "&lt;");
        retVal = retVal.replace(/[>]/g, "&gt;");
        return retVal;
    }
    return val;
}

window.onerror = trapError;