/*
 Function Name: ContentLoader
 Arguments: 
  URL: the URL to which the request is sent
  METHOD: the method used to send the request.  If this is set to JSON or XML, the POST method will be used.
  CALLBACK: the function to call when the server response is complete
  RESULTDIV: the name of the div that will contain the output
  PARAMS: an object with properties and values
 Returns: Nothing
 Notes: Used to create and send an XMLHttpRequest object and call a specified callback function when the server response is complete.
*/
function ContentLoader(URL,METHOD,CALLBACK,RESULTDIV,PARAMS)
{
 this.xmlhttp=null;
 this.url = URL;
 this.method = (typeof METHOD == "undefined" || typeof METHOD == null) ? "GET" : METHOD.toUpperCase();
 this.callBack=CALLBACK;
 this.resultDiv = (typeof RESULTDIV == "string") ? document.getElementById(RESULTDIV) : RESULTDIV;
 this.resultDivString = RESULTDIV;
 this.params = (typeof PARAMS == "undefined") ? null : PARAMS;
 this._loadAjax();
}

ContentLoader.prototype._loadAjax=function()
{ 
 var PostQS;
 if (this.method=="POST")
 {
  PostQS = this._createQueryString();
 }
 else //GET OR HEAD
 {
  this.url = this.url + "?" + this._createQueryString();
  PostQS = null;
 }
 
 if ( this.xmlhttp=this._createXHR() )
 {
  try
  {
   var loader=this;
   this.xmlhttp.onreadystatechange=function() 
   {
          loader._onReadyState.call(loader);
   }
   this.xmlhttp.open(this.method,this.url,true);
   
   if (this.method=="POST")
   {
    this.xmlhttp.setRequestHeader("Content-Type","application/x-www-form-urlencoded;");
   }
   this.xmlhttp.send(PostQS);
  }
  catch(exc)
  {
   alert("ERROR: " + exc.message);
  }
 }
 else
 {
  alert("ERROR: AJAX NOT SUPPORTED");
 }
}

ContentLoader.prototype._onReadyState=function()
{
 if (this.xmlhttp.readyState==4 && this.xmlhttp.status == 200)
 {
  if (this.callBack) this.callBack.call(this);
 }
 else if (this.xmlhttp.readyState==4)
 {
  alert("Error: " + this.xmlhttp.responseText);
 }
}

/*
 Function Name: _createXHR
 Arguments: none
 Returns: browser-specific xmlhttp object or false
*/
ContentLoader.prototype._createXHR=function()
{
 try
 {
  xmlhttp = new XMLHttpRequest();
 }
 catch(exc1)
 {
  var ieXmlHttpVersions = new Array();
  /*ieXmlHttpVersions[ieXmlHttpVersions.length] = "MSXML2.XMLHttp.7.0";
  ieXmlHttpVersions[ieXmlHttpVersions.length] = "MSXML2.XMLHttp.6.0";
  ieXmlHttpVersions[ieXmlHttpVersions.length] = "MSXML2.XMLHttp.5.0";
  ieXmlHttpVersions[ieXmlHttpVersions.length] = "MSXML2.XMLHttp.4.0";
  ieXmlHttpVersions[ieXmlHttpVersions.length] = "MSXML2.XMLHttp.3.0";
  ieXmlHttpVersions[ieXmlHttpVersions.length] = "MSXML2.XMLHttp";*/
  ieXmlHttpVersions[ieXmlHttpVersions.length] = "Microsoft.XMLHTTP";
  
  var i;
  for (i=0; i < ieXmlHttpVersions.length; i++)
  {
   try
   {
    xmlhttp = new ActiveXObject(ieXmlHttpVersions[i]);
    break;
   }
   catch (exc2)
   {
    alert(ieXmlHttpVersions[i] + " not supported.");
   }
  }
 }
 return xmlhttp;
}

ContentLoader.prototype._createQueryString=function()
{
 var qs="timestamp=" + new Date().getTime();
 if (typeof this.params == "object") //if no arguments are passed, arguments has a length of 1 and arguments[0] is undefined.
 {
  for (i in this.params)
  {
   qs += "&" + i + "=" + this.params[i];
  }
 }
 return qs;
}