var xmlHTTP=null;
var xmldoc = new Object;
var slideTot;
var tutNum;
var textArray = new Array;

function GetXmlHttpObject(){
	try{    
    		xmlHTTP = new XMLHttpRequest();
	}catch (e){
		try{      
    			xmlHTTP = new ActiveXObject("Msxml2.XMLHTTP");
		}catch (e){
			xmlHTTP = new ActiveXObject("Microsoft.XMLHTTP");
		}
  }
  return xmlHTTP;  
}


function setUpSlide(newNum, whichTut){
	slideTot = newNum;
	tutNum = whichTut;
	getFile();
	
}
function getFile(){
	xmlHTTP=GetXmlHttpObject();
	if (xmlHTTP==null){
  		alert ("Your browser does not support AJAX!");
  		return;
  	}
	url= "tutorialImages/tutorial"+tutNum+".txt";
	xmlHTTP.onreadystatechange=createTextArray;
	xmlHTTP.open("GET",url,true);
	xmlHTTP.send(null);
}
function createTextArray(){
	if (xmlHTTP.readyState == 4) {
		if (xmlHTTP.status == 200) {
			xmldoc = xmlHTTP.responseText;	
			textArray=xmldoc.split("--");
			changeSlide(0);
			document.getElementById("text2").innerHTML = textArray[0];
		} else {
            alert('There was a problem with the request.');
		}
	}
}

function changeSlide(arg){
	if(arg ==0){
		slideNum = 1;
	}else if(arg==-1){
		if(slideNum!=1){
			slideNum-=1;
		}else{
			slideNum=1;
		}
	}else if(arg==1){
		if(slideNum<slideTot){
			slideNum+=1;
		}else{
			slideNum=slideTot;
		}
	}
	filename = "tutorial"+tutNum+"_slide"+slideNum+".jpg";
	url = "tutorialImages/Tutorial"+tutNum+"Opt/"+filename;
	imgText = "<img align = 'center' width = '550px' src = '"+url+"' alt = '"+filename+"'>";
	
	if(textArray[slideNum]==undefined || textArray[slideNum] == ""){
		transText = "See references above";
	}else{
		transText = textArray[slideNum];
	}
	document.getElementById("image").innerHTML = imgText;
	document.getElementById("text").innerHTML = transText;
}