var hasLoaded = false;

//constants
var NUMBER_OF_PICTURES = 0;
var PICTURES_ID_PREFIX = "picGalleryNoScript_";
var PICTURES_LINK_ID_PREFIX = "pictureLink_";
var currentPic = 0;

//divs
var NEXT_DIV = "next";
var BACK_DIV = "back";
var NAVBOX_DIV = "navBox";

function init() {
	hasLoaded = true;
	NUMBER_OF_PICTURES = countPics();
	showDiv(0);
	if(NUMBER_OF_PICTURES==1){
		document.getElementById('navBox').style.display='none';
	}
}

function countPics(){
	//this function saves us hardcoding in the number of images we are using (upto 100)
	var picCount = 0;
	for(var i = 0; i < 100; i++) {
		var id = PICTURES_ID_PREFIX + i;	
		var node = document.getElementById(id);
		if(node) {
			picCount++;
		}
	}
	return picCount;
}

function showDiv(nDiv) {	
	for(var i = 0; i < NUMBER_OF_PICTURES; i++) {
		var buttonid = i;
		var id = PICTURES_ID_PREFIX + i;	
		var node = document.getElementById(id);
		if(node && i==nDiv) {
			node.style.display='block';		
			node.style.visibility='visible';						
			currentPic = i;
		} else if(node) {
			node.style.display='none';
			node.style.visibility='hidden';
		}		
	}
	//do not display back button when first image is displayed, do not display next button when last image in sequence is displayed
	if(nDiv==0){
		document.getElementById('back').style.visibility='hidden';
	}
	else{
		document.getElementById('back').style.visibility='visible';
	}
	if(nDiv==NUMBER_OF_PICTURES-1){
		document.getElementById('next').style.visibility='hidden';
	}
	else{
		document.getElementById('next').style.visibility='visible';
	}
}

function showDivNext() {
	if(currentPic < (NUMBER_OF_PICTURES - 1)) {
		showDiv(currentPic + 1);	
	}   
}

function showDivPrev() {
	if(currentPic > 0) {
		showDiv(currentPic - 1);
	}
}

if (document.getElementById) {
	document.onLoad = init();
}