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

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

        //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);
                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);
                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;
                        }
                }
                r.onreadystatechange = function()
                {
                        if (r.readyState != 4)
                                return;

                        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';
                                }
                        }

                        delete r;
                }
                if (xajaxDebug) this.DebugMessage("Calling "+sFunction +" uri="+uri+" (post:"+ postData +")");
                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("oldData=document.getElementById('"+element+"')."+attribute);
                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) {
                        alert("Error: the XML response that was returned from the server cannot be processed.");
                        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("objElement."+property+"=data;");
                                                }
                                        }
                                        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();