var slideshow_timer;
var slidesArray;
var thisSlide = -1;	

//create image objects to preload images into
var next_background_image = new Image;
var next_mis_banner_image = new Image;

var thisRequest;

function startSlideshow(){	
	thisRequest = new makeRequest(url);
}

function makeRequest(url) {
        var http_request = false;

        if (window.XMLHttpRequest) { // Mozilla, Safari, ...
            http_request = new XMLHttpRequest();
            if (http_request.overrideMimeType) {
                http_request.overrideMimeType('text/xml');
            }
        } else if (window.ActiveXObject) { // IE
            try {
                http_request = new ActiveXObject("Msxml2.XMLHTTP");
            } catch (e) {
                try {
                http_request = new ActiveXObject("Microsoft.XMLHTTP");
                } catch (e) {}
            }
        }

        if (!http_request) {
            alert('Giving up :( Cannot create an XMLHTTP instance');
            return false;
        }
       http_request.onreadystatechange = function() { 
			slidesArray = alertContents(http_request);
				
			if(slidesArray != null){

				///////////////////
				displaySlide("");
				//////////////////
			}
				
			else{
			}	
		
	  };
	
       http_request.open('GET', url, true);
       http_request.send(null);
   
 }


	
function displaySlide(slide_name){
	

	numberSlides = slidesArray.length;	
	if (slide_name != "" ){
		for (var n=0; n < slidesArray.length; n++){
			if (slidesArray[n]["name"] == slide_name){
				thisSlide = n;				
			}
		}

	}else{

		thisSlide++
		switch(true){
			case (thisSlide >= numberSlides):
				thisSlide= 0;
				break;
			case (thisSlide < 0):
				thisSlide = numberSlides;
				break;
		}
	}
	nextSlide_index = thisSlide+1;	
	if (nextSlide_index >= numberSlides){
		nextSlide_index= 0;
	}
	for(var l=0; l < theDivArray.length; l++){
		len = theDivArray.length;
		//get the div name and the corresponding xmlTag name
		thisDivTag = theDivArray[l];
		thisXMLTag = xmlTagsArray[l];
		//get the content of the xmlTag from slide object in the slideArray
		tagContent = slidesArray[thisSlide][thisXMLTag];
		//get the div
		var divContainer = document.getElementById(thisDivTag);
		if (divContainer != null){

			//check for special cases where extra markup or logic is needed (ie, images)
			switch (thisDivTag){
				case "background_image":
					//check to make sure the preloaded image is the right one
					if (next_background_image.src != tagContent){
						next_background_image.src = tagContent;
					}
					var imageElement = divContainer.getElementsByTagName("img")[0];
					imageElement.src = next_background_image.src;
					imageElement.width='800'; 
					imageElement.height='480';
					next_background_image.src = slidesArray[nextSlide_index][thisXMLTag];
	
					break;		
				case "mis_banner":				
					//check to make sure the preloaded image is the right one
					if (next_mis_banner_image.src != tagContent){
						next_mis_banner_image.src = tagContent;
					}
					var imageElement = divContainer.getElementsByTagName("img")[0];
					imageElement.src = next_mis_banner_image.src;
					imageElement.width='676'; 
					imageElement.height='90';
					next_mis_banner_image.src = slidesArray[nextSlide_index][thisXMLTag];
					break;
				default:
					divContainer.innerHTML = tagContent;
				
			}
		}
	
	}
	//set non-content parameters:
	layout  = slidesArray[thisSlide]["layout"];	
	theme  = slidesArray[thisSlide]["theme"];	
	duration  = slidesArray[thisSlide]["duration"];	
	thisTheme = manageTheme();
	
	//preload image_corners for next slide
	var next_theme_root = "themes/" + slidesArray[nextSlide_index]["theme"] + "/theme";
		var ul = new Image();
		ul.src = next_theme_root + "_round_ul.gif";
		var ll = new Image();
		ll.src = next_theme_root + "_round_ll.gif";
		var ur = new Image();
		ur.src = next_theme_root + "_round_ur.gif";
		var lr = new Image();
		lr.src = next_theme_root + "_round_lr.gif";
		var fcb = new Image();
		fcb.src = next_theme_root + "_b.gif";
		var fcc = new Image();
		fcc.src = next_theme_root + "_c.gif";


	clearTimeout(slideshow_timer);
	slideshow_timer = setTimeout('displaySlide("")', duration);
}


function alertContents(http_request, xmlTagArray, theDivArray, theVariablesArray) {

	if (http_request.readyState == 4) {
		if (http_request.status == 200) {
			xmlContents = processXMLContents(http_request);  
		return xmlContents;
		}

	else {
			alert('There was a problem with the request.');
		}
	}
}

	
function processXMLContents(http_request){
	
	var slidesArray = Array();
			
	var xmlResponse = http_request.responseXML;
	var xmlRoot = xmlResponse.documentElement;
	var xmlSlides = xmlRoot.getElementsByTagName('slide');
	
	//parse xmlSlides into an array of slide objects:
	
	for(var i=0; i < xmlSlides.length; i++){
		var slide = Object();
		var slide_attributes = xmlSlides.item(i).attributes;
		for (var a=0; a < slide_attributes.length;a++){
			if  (slide_attributes[a].nodeValue != null){					
 				slide[slide_attributes[a].nodeName] = slide_attributes[a].nodeValue;
			}
		}
		if (xmlSlides.item(i).hasChildNodes()){
			var slide_childNodes = xmlSlides.item(i).childNodes;
			for (var c=0;c< slide_childNodes.length;c++){
				if (slide_childNodes[c].nodeType==1 && slide_childNodes[c].hasChildNodes() && slide_childNodes[c].firstChild.nodeType==3 ){
				slide[slide_childNodes[c].nodeName] = slide_childNodes[c].firstChild.data;
				}
			}
		}
		slidesArray.push(slide);
	}
	return slidesArray;
}//end function