var intPosition = 0;
var intScrollTo = 0;
var intPageHeight = 467;
var intNumPages = 3;
var intPageIndex = 1;
var intScrollDelay = 20;

function scroll()
{
	var intMinPosition = (1 - intNumPages) * intPageHeight;

	if (intScrollTo != intPosition)
	{
		var intScrollBy =  intScrollTo - intPosition;
		
		if (intScrollBy > 10) intPosition += 10;
		else if (intScrollBy < -10) intPosition -= 10;
		else intPosition += intScrollBy;

		if (intScrollTo == intMinPosition) document.getElementById('gonext').style.visibility= "hidden";
		else document.getElementById('gonext').style.visibility= "visible";
		if (intScrollTo == 0) document.getElementById('goprevious').style.visibility= "hidden";
		else document.getElementById('goprevious').style.visibility= "visible";

		document.getElementById('scrollwindow').style.top = intPosition + "px";
		setTimeout(scroll, intScrollDelay); 
	}
}

function flip_to_previous()
{
	if (intPosition == intScrollTo)
	{
		intScrollTo = intPosition +  intPageHeight;
		intPageIndex--;
		if (intScrollTo > 0)
		{
			intScrollTo = 0;
			intPageIndex = 1;
		}
		if (intPageIndex == 1) document.getElementById('prevarrow').style.visibility = 'hidden';
		else document.getElementById('prevarrow').style.visibility = 'visible';
		if (intPageIndex == intNumPages) document.getElementById('nextarrow').style.visibility = 'hidden';
		else document.getElementById('nextarrow').style.visibility = 'visible';
		intScrollDelay = (500 * 10) / 450;
		scroll();
	}
}

function flip_to_next()
{
	var intMinPosition = (1 - intNumPages) * intPageHeight;

	if (intPosition == intScrollTo)
	{
		intScrollTo = intPosition -  intPageHeight;
		intPageIndex++;
		if (intScrollTo < intMinPosition)
		{
			intScrollTo = intMinPosition;
			intPageIndex = intNumPages;
		}
		if (intPageIndex == 1) document.getElementById('prevarrow').style.visibility = 'hidden';
		else document.getElementById('prevarrow').style.visibility = 'visible';
		if (intPageIndex == intNumPages) document.getElementById('nextarrow').style.visibility = 'hidden';
		else document.getElementById('nextarrow').style.visibility = 'visible';
		intScrollDelay = (500 * 10) / 450;
		scroll();
	}
}

function flip_scroll (event)
{
	event.cancelBubble = true;
	event.returnValue = false;
	if (event.preventDefault) event.preventDefault()
	if (intPosition == intScrollTo)
	{
		if ((event.detail < 0) || (event.wheelDelta > 0))
		{
			flip_to_previous();
		}
		else if ((event.detail > 0) || (event.wheelDelta < 0))
		{
			flip_to_next();
		}
	}
}

function scroll_listen()
{
	var element = document.getElementById('scrollwindow');
	if (element.addEventListener)
	{
		element.addEventListener("DOMMouseScroll", flip_scroll, false);
		element.addEventListener("mousewheel", flip_scroll, false);
	}
	else if (element.attachEvent)
	{
		element.attachEvent("onmousewheel", flip_scroll);
	}
}