function Xajax()
{
  if (typeof xajaxDebug == 'undefined') { var xajaxDebug = false;}

  if (xajaxDebug) this.DebugMessage = function(text) { alert("Xajax Debug:\n " + text) };

  this.workId = 'xajaxWork'+ new Date().getTime();
  this.depth = 0;
  this.logging = '';
  this.loop = '';

  //Get the XMLHttpRequest Object
  this.getRequestObject = function()
  {
    if (xajaxDebug) this.DebugMessage("Initializing Request Object..");
    var req;
    try
    {
      req=new ActiveXObject("Msxml2.XMLHTTP");
    }
    catch (e)
    {
      try
      {
        req=new ActiveXObject("Microsoft.XMLHTTP");
      }
      catch (e2)
      {
        req=null;
      }
    }
    if(!req && typeof XMLHttpRequest != "undefined")
      req = new XMLHttpRequest();

      if (xajaxDebug) {
        if (!req) this.DebugMessage("Request Object Instantiation failed.");
      }

    return req;
  }

  // xajax.$() is shorthand for document.getElementById()
  this.$ = function(sId)
  {
    if (!sId) {
      return null;
    }
    var returnObj = document.getElementById(sId);
    if (xajaxDebug && !returnObj && sId != this.workId) {
      this.DebugMessage("Element with the id \"" + sId + "\" not found.");
    }
    return returnObj;
  }

  // xajax.include(sFileName) dynamically includes an external javascript file
  this.include = function(sFileName)
  {
    var objHead = document.getElementsByTagName('head');
    var objScript = document.createElement('script');
    objScript.type = 'text/javascript';
    objScript.src = sFileName;
    objHead[0].appendChild(objScript);
  }

  // xajax.addHandler adds an event handler to an element
  this.addHandler = function(sElementId, sEvent, sFunctionName)
  {
    if (window.addEventListener)
    {
      eval("this.$('"+sElementId+"').addEventListener('"+sEvent+"',"+sFunctionName+",false);");
    }
    else
    {
      eval("this.$('"+sElementId+"').attachEvent('on"+sEvent+"',"+sFunctionName+",false);");
    }
  }

  // xajax.removeHandler removes an event handler from an element
  this.removeHandler = function(sElementId, sEvent, sFunctionName)
  {
    if (window.addEventListener)
    {
      eval("this.$('"+sElementId+"').removeEventListener('"+sEvent+"',"+sFunctionName+",false);");
    }
    else
    {
      eval("this.$('"+sElementId+"').detachEvent('on"+sEvent+"',"+sFunctionName+",false);");
    }
  }

  // xajax.create creates a new child node under a parent
  this.create = function(sParentId, sTag, sId)
  {
    var objParent = this.$(sParentId);
    if(!objParent)return;
    objElement = document.createElement(sTag);
    objElement.setAttribute('id',sId);
    objParent.appendChild(objElement);
  }

  // xajax.insert inserts a new node before another node
  this.insert = function(sBeforeId, sTag, sId)
  {
    var objSibling = this.$(sBeforeId);
    objElement = document.createElement(sTag);
    objElement.setAttribute('id',sId);
    objSibling.parentNode.insertBefore(objElement, objSibling);
  }

  this.getInput = function(sType, sName, sId)
  {
    var Obj;
    if (sType == "radio" && !window.addEventListener)
    {
      Obj = document.createElement('<input type="radio" id="'+sId+'" name="'+sName+'">');
    }
    else
    {
      Obj = document.createElement('input');
      Obj.setAttribute('type',sType);
      Obj.setAttribute('name',sName);
      Obj.setAttribute('id',sId);
    }
    return Obj;
  }

  // xajax.createInput creates a new input node under a parent
  this.createInput = function(sParentId, sType, sName, sId)
  {
    var objParent = this.$(sParentId);
    if(!objParent)return;
    var objElement = this.getInput(sType, sName, sId);
    objParent.appendChild(objElement);
  }

  // xajax.insertInput creates a new input node before another node
  this.insertInput = function(sBeforeId, sType, sName, sId)
  {
    var objSibling = this.$(sBeforeId);
    var objElement = this.getInput(sType, sName, sId);
    objSibling.parentNode.insertBefore(objElement, objSibling);
  }

  // xajax.remove deletes an element
  this.remove = function(sId)
  {
    objElement = this.$(sId);
    if (objElement.parentNode && objElement.parentNode.removeChild)
    {
      objElement.parentNode.removeChild(objElement);
    }
  }

  //xajax.replace searches for text in an attribute of an element and replaces it
  //with a different text
  this.replace = function(sId,sAttribute,sSearch,sReplace)
  {
    var bFunction = false;

    if (sAttribute == "innerHTML")
      sSearch = this.getBrowserHTML(sSearch);

    eval("var txt=document.getElementById('"+sId+"')."+sAttribute);
    if (typeof txt == "function")
        {
            txt = txt.toString();
            bFunction = true;
        }
    if (txt.indexOf(sSearch)>-1)
    {
      var newTxt = '';
      while (txt.indexOf(sSearch) > -1)
      {
        x = txt.indexOf(sSearch)+sSearch.length+1;
        newTxt += txt.substr(0,x).replace(sSearch,sReplace);
        txt = txt.substr(x,txt.length-x);
      }
      newTxt += txt;
      if (bFunction)
      {
        eval("newTxt =" + newTxt);
        eval('this.$("'+sId+'").'+sAttribute+'=newTxt;');
      }
      else if (this.willChange(sId,sAttribute,newTxt))
      {
        eval('this.$("'+sId+'").'+sAttribute+'=newTxt;');
      }
    }
  }

  // xajax.getFormValues() builds a query string XML message from the elements of a form object
  this.getFormValues = function(frm)
  {
    var objForm;
    var submitDisabledElements = false;
    if (arguments.length > 1 && arguments[1] == true)
      submitDisabledElements = true;

    if (typeof(frm) == "string")
      objForm = this.$(frm);
    else
      objForm = frm;
    var sXml = "<xjxquery><q>";
    if (objForm && objForm.tagName == 'FORM')
    {
      var formElements = objForm.elements;
      for( var i=0; i < formElements.length; i++)
      {
        if (formElements[i].type && (formElements[i].type == 'radio' || formElements[i].type == 'checkbox') && formElements[i].checked == false)
          continue;
        if (formElements[i].disabled && formElements[i].disabled == true && submitDisabledElements == false) continue;
        var name = formElements[i].name;
        if (name)
        {
          if (sXml != '<xjxquery><q>')
            sXml += '&';
          if(formElements[i].type=='select-multiple')
          {
            for (var j = 0; j < formElements[i].length; j++)
            {
              if (formElements[i].options[j].selected == true)   sXml += name+"="+encodeURIComponent(formElements[i].options[j].value)+"&";
            }
          }
          else
          {
            sXml += name+"="+encodeURIComponent(formElements[i].value);
          }
        }
      }
    }

    sXml +="</q></xjxquery>";

    return sXml;
  }

  // Generates an XML message that xajax can understand from a javascript object
  this.objectToXML = function(obj)
  {
    var sXml = "<xjxobj>";
    for (i in obj)
    {
      try
      {
        if (i == 'constructor')
          continue;
        if (obj[i] && typeof(obj[i]) == 'function')
          continue;

        var key = i;
        var value = obj[i];
        if (value && typeof(value)=="object" &&
          (value.constructor == Array
           ) && this.depth <= 50)
        {
          this.depth++;
          value = this.objectToXML(value);
          this.depth--;
        }

        sXml += "<e><k>"+key+"</k><v>"+value+"</v></e>";

      }
      catch(e)
      {
        if (xajaxDebug) this.DebugMessage(e);
      }
    }
    sXml += "</xjxobj>";

    return sXml;
  }

  // Sends a XMLHttpRequest to call the specified PHP function on the server
  // * sRequestType is optional -- defaults to POST
  this.call = function(sFunction, aArgs, sRequestType)
  {
    var i,r,postData;
    if (document.body && xajaxWaitCursor)
      document.body.style.cursor = 'wait';
    if (xajaxStatusMessages == true) window.status = 'Sending Request...';
    if (xajaxDebug) this.DebugMessage("Starting xajax...");
    if (sRequestType == null) {
       var xajaxRequestType = xajaxDefinedPost;
    }
    else {
      var xajaxRequestType = sRequestType;
    }
    var uri = xajaxRequestUri;
    var value;
    switch(xajaxRequestType)
    {
      case xajaxDefinedGet:{
        var uriGet = uri.indexOf("?")==-1?"?xajax="+encodeURIComponent(sFunction):"&xajax="+encodeURIComponent(sFunction);
        if (aArgs) {
          for (i = 0; i<aArgs.length; i++)
          {
            value = aArgs[i];
            if (typeof(value)=="object")
              value = this.objectToXML(value);
            uriGet += "&xajaxargs[]="+encodeURIComponent(value);
          }
        }
        uriGet += "&xajaxr=" + new Date().getTime();
        uri += uriGet;
        postData = null;
        } break;
      case xajaxDefinedPost:{
        postData = "xajax="+encodeURIComponent(sFunction);
        postData += "&xajaxr="+new Date().getTime();
        if (aArgs) {
          for (i = 0; i <aArgs.length; i++)
          {
            value = aArgs[i];
            if (typeof(value)=="object")
              value = this.objectToXML(value);
            postData = postData+"&xajaxargs[]="+encodeURIComponent(value);
          }
        }
        } break;
      default:
        alert("Illegal request type: " + xajaxRequestType); return false; break;
    }
    r = this.getRequestObject();
    if (!r) return false;
    r.open(xajaxRequestType==xajaxDefinedGet?"GET":"POST", uri, true);
    if (xajaxRequestType == xajaxDefinedPost)
    {
      try
      {
        r.setRequestHeader("Method", "POST " + uri + " HTTP/1.1");
        r.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
      }
      catch(e)
      {
        alert("Your browser does not appear to  support asynchronous requests using POST.");
        return false;
      }
    }

    xajax.loop = 0;
    xajax.logging = "Calling "+sFunction +" uri="+uri+" (post:"+ postData +")";

    r.onreadystatechange = function()
    {
      if (typeof xajaxDebug == 'undefined') { var xajaxDebug = false;}

      try
      {
        xajax.loop+=1;
        if (r.readyState != 4){
          xajax.logging+=',loop '+xajax.loop+'';
          return;
        }
        xajax.logging+=',ready,status='+r.status;

        if (r.status==200)
        {
          if (xajaxDebug && r.responseText.length < 1000) xajax.DebugMessage("Received:\n" + r.responseText);
          else if (xajaxDebug) xajax.DebugMessage("Received:\n" + r.responseText.substr(0,1000)+"...\n[long response]\n...</xajax>");
          if (r.responseXML)
            xajax.processResponse(r.responseXML);
          else {
            //alert("Error: the XML response that was returned from the server is invalid.");
            document.body.style.cursor = 'default';
            if (xajaxStatusMessages == true) window.status = 'Invalid XML response error';

            xajax.logging+= "";
            xajax.logging+= "content is no XML! ";
            xajax.logging+= "Response-Data="+r.responseText+"";
            xajax_get_function('xlog',xajax.logging);

          }
        }else{
          xajax.logging+= " Error fetching Response "+r.statusText+" , Response-Data="+r.responseText+"";
          xajax_get_function('xlog',xajax.logging);
        }
      }
      catch(e)
      {
        this.logging+="Error fetching XML-Responsedata";
        xajax_get_function('xlog',xajax.logging);
      }
      delete r;
    }
    xajax.loop=0;
    xajax.logging='';
    r.send(postData);
    if (xajaxStatusMessages == true) window.status = 'Waiting for data...';
    delete r;
    return true;
  }

  //Gets the text as it would be if it were being retrieved from
  //the innerHTML property in the current browser
  this.getBrowserHTML = function(html)
  {
    tmpXajax = this.$(this.workId);
    if (tmpXajax == null)
    {
      tmpXajax = document.createElement("div");
      tmpXajax.setAttribute('id',this.workId);
      tmpXajax.style.display = "none";
      tmpXajax.style.visibility = "hidden";
      document.body.appendChild(tmpXajax);
    }
    tmpXajax.innerHTML = html;
    var browserHTML = tmpXajax.innerHTML;
    tmpXajax.innerHTML = '';

    return browserHTML;
  }

  // Tests if the new Data is the same as the extant data
  this.willChange = function(element, attribute, newData)
  {
    if (!document.body)
    {
      return true;
    }
    var oldData;
    if (attribute == "innerHTML")
    {
      newData = this.getBrowserHTML(newData);
    }
    eval("try{oldData=document.getElementById('"+element+"')."+attribute+"}catch(e){}");
    if (newData != oldData)
      return true;

    return false;
  }

  //Process XML xajaxResponses returned from the request
  this.processResponse = function(xml)
  {
    if (xajaxStatusMessages == true) window.status = 'Processing...';
    var tmpXajax = null;
    xml = xml.documentElement;
    if (xml == null) {
      document.body.style.cursor = 'default';
      if (xajaxStatusMessages == true) window.status = 'XML response processing error';
      return;
    }
    for (i=0; i<xml.childNodes.length; i++)
    {
      if (xml.childNodes[i].nodeName == "cmd")
      {
        var cmd;
        var id;
        var property;
        var data;
        var search;
        var type;
        var before;

        for (j=0; j<xml.childNodes[i].attributes.length; j++)
        {
          if (xml.childNodes[i].attributes[j].name == "n")
          {
            cmd = xml.childNodes[i].attributes[j].value;
          }
          if (xml.childNodes[i].attributes[j].name == "t")
          {
            id = xml.childNodes[i].attributes[j].value;
          }
          if (xml.childNodes[i].attributes[j].name == "p")
          {
            property = xml.childNodes[i].attributes[j].value;
          }
          if (xml.childNodes[i].attributes[j].name == "c")
          {
            type = xml.childNodes[i].attributes[j].value;
          }
        }
        if (xml.childNodes[i].childNodes.length > 1)
        {
          for (j=0; j<xml.childNodes[i].childNodes.length; j++)
          {
            if (xml.childNodes[i].childNodes[j].nodeName == "s")
            {
              if (xml.childNodes[i].childNodes[j].firstChild)
                search = xml.childNodes[i].childNodes[j].firstChild.nodeValue;
            }
            if (xml.childNodes[i].childNodes[j].nodeName == "r")
            {
              if (xml.childNodes[i].childNodes[j].firstChild)
                data = xml.childNodes[i].childNodes[j].firstChild.data;
            }
          }
        }
        else if (xml.childNodes[i].firstChild)
          data = xml.childNodes[i].firstChild.nodeValue;
        else
          data = "";

        var objElement = this.$(id);
        try
        {
          if (cmd=="al")
          {
            alert(data);
          }
          if (cmd=="js")
          {
            eval(data);
          }
          if (cmd=="in")
          {
            this.include(data);
          }
          if (cmd=="as")
          {
            if (this.willChange(id,property,data))
            {
              eval("try{objElement."+property+"=data;}catch(e){}");
            }
          }
          if (cmd=="ap")
          {
            eval("objElement."+property+"+=data");
          }
          if (cmd=="pp")
          {
            eval("objElement."+property+"=data+objElement."+property);
          }
          if (cmd=="rp")
          {
            this.replace(id,property,search,data)
          }
          if (cmd=="rm")
          {
            this.remove(id);
          }
          if (cmd=="ce")
          {
            this.create(id,data,property);
          }
          if (cmd=="ie")
          {
            this.insert(id,data,property);
          }
          if (cmd=="ci")
          {
            this.createInput(id,type,data,property);
          }
          if (cmd=="ii")
          {
            this.insertInput(id,type,data,property);
          }
          if (cmd=="ev")
          {
            eval("this.$('"+id+"')."+property+"= function(){"+data+";}");
          }
          if (cmd=="ah")
          {
            this.addHandler(id, property, data);
          }
          if (cmd=="rh")
          {
            this.removeHandler(id, property, data);
          }
        }
        catch(e)
        {
          alert(e);
        }
        delete objElement;
        delete cmd;
        delete id;
        delete property;
        delete search;
        delete data;
        delete type;
        delete before;
      }
    }
    delete xml;
    document.body.style.cursor = 'default';
    if (xajaxStatusMessages == true) window.status = 'Done';
  }
}

var xajax = new Xajax();