var thumbLimit = 4;
var albumLimit = 12;
var imageDir = 'images/';
var thumbPrep = imageDir+'t';
var thumbStartIndex = 0;
var curImg = 0;
var interval = 3000;
var threadPointer;
var running = true;

function initShow()
{
	for(i=1;i<=thumbLimit;i++)
	{
		var temp = 't'+i;
		//alert(temp);
		var imag = document.getElementById(temp);
		imag.src = (thumbPrep+i+'.jpg');
	}
	switchMain();
	threadPointer = setInterval("next()",interval);
}

function switchPlay()
{
	if(running)
		pause();
	else
		play();
}

function pause()
{
	clearInterval(threadPointer);
	running = false;
}

function play()
{
	threadPointer = setInterval("next()",interval);
	running = true;
}

function update(index)
{
	curImg = parseInt(index.id.substring(1))+thumbStartIndex;
	switchMain();
}

function switchMain()
{
	var mainImag = document.getElementById('mainImg');
	mainImag.src = imageDir+curImg+'.jpg';
}

function forward()
{
    var lastIndex = thumbLimit+thumbStartIndex;
    if(lastIndex<albumLimit)
    {        
        thumbStartIndex++;
        for(i=1;i<=thumbLimit;i++)
        {
            var temp = 't'+i;
            //alert(temp);
            var imag = document.getElementById(temp);
            imag.src = (thumbPrep+(i+thumbStartIndex)+'.jpg');
        }
    }
}

function backward()
{
    if(thumbStartIndex>0)
    {        
        thumbStartIndex--;
        for(i=1;i<=thumbLimit;i++)
        {
            var temp = 't'+i;
            //alert(temp);
            var imag = document.getElementById(temp);
            imag.src = (thumbPrep+(i+thumbStartIndex)+'.jpg');
        }
    }    
}

function next()
{
	if(curImg<albumLimit)
	{
		curImg++;		
		switchMain();
	}
}

function previous()
{
	if(curImg>1)
	{
		curImg--;
		switchMain();
	}
}