var otimer, opacityCheck, overlayDiv, odir, showset, hideset, currentSet, numSets, inprogress;
currentSet = 1;
function setupSets( ns, cs )
{
	numSets = ns;
	currentSet = cs;
	opacityCheck = 0;
	odir = 1;
	inprogress = false;
}

function changeSet( h, s )
{
	inprogress = true;
	showset = document.getElementById( s );
	hideset = document.getElementById( h );
	otimer = setInterval( "overlayOpacity()", 50 );
	overlayDiv = document.getElementById( "thumboverlay" );
}

function overlayOpacity()
{
	overlayDiv.style.display = "block";
	opacityCheck += odir;
	if( odir == 1 && opacityCheck > 10 )
	{
		//done, do what needs to be done here and then change direction
		hideset.style.display = "none";
		showset.style.display = "block";
		odir = -1;
		opacityCheck = 10;	
	}
	else if( odir == -1 && opacityCheck < 1 )
	{
		//done, hide and stop interval
		clearInterval( otimer );
		odir = 1;
		opacityCheck = 0;
		overlayDiv.style.display = "none";
		inprogress = false;
		return;
	}
	//Set opacity
	overlayDiv.style.opacity = opacityCheck/10;
	overlayDiv.style.filter = "alpha(opacity = " + opacityCheck*10 +")";

}
function nextSet()
{
	if( inprogress ) return;
	if( currentSet >= numSets ) return;
	currentSet++;
	if( currentSet >= numSets )
	{
		//hide forward button
		document.getElementById( "aright" ).style.visibility = "hidden";
		
	}
	//show back button
	document.getElementById( "aleft" ).style.visibility = "visible";
	
	changeSet( "t"+(currentSet-1), "t"+currentSet );
	
}

function prevSet()
{
	if( inprogress ) return;
	if( currentSet <= 1 ) return;
	currentSet--;
	if( currentSet <= 1 )
	{
		//hide back button
		document.getElementById( "aleft" ).style.visibility = "hidden";
		
	}
	//show forward button
	document.getElementById( "aright" ).style.visibility = "visible";
	changeSet( "t"+(currentSet+1), "t"+currentSet );
}

function goSet( set )
{
	if( set > numSets || set < 1 ) set = 1;
	changeSet( "t"+currentSet, "t"+set );
	currentSet = set;
	if( currentSet > 1 ) document.getElementById( "aleft" ).style.visibility = "visible";
	else document.getElementById( "aleft" ).style.visibility = "hidden";
	
	if( currentSet < numSets ) document.getElementById( "aright" ).style.visibility = "visible";
	else document.getElementById( "aright" ).style.visibility = "hidden";
}