var containerHeight = 270;
var itemHeight = 270;
var divItems;
var isRunning = false;

function getTop()
{
	divItems = document.getElementById("storyWrapper");
	if (divItems.currentStyle)
		var top = parseInt(divItems.currentStyle["top"]);
	else if (window.getComputedStyle)
		var top = parseInt(document.defaultView.getComputedStyle(divItems, null).getPropertyValue("top"));
	return top;
}

function checkButtons()
{
	divItems = document.getElementById("storyWrapper");
	var currentPosition = parseInt(getTop());

    if (currentPosition >= 0)
		document.getElementById("previous").className = "btnUp disabled";
	else
		document.getElementById("previous").className = "btnUp";
		
	if (Math.abs(currentPosition) + containerHeight >= divItems.offsetHeight)
		document.getElementById("next").className = "btnDown disabled";
	else
		document.getElementById("next").className = "btnDown";
}

function previousBtn()
{
	divItems = document.getElementById("storyWrapper");
	var currentPosition = parseInt(getTop());

	if ((currentPosition + itemHeight) <= 0 && isRunning == false)
	{
		isRunning = true;
		moveUp((currentPosition + itemHeight), itemHeight);
	}
}

function moveUp(destination, distance)
{
	divItems = document.getElementById("storyWrapper");
	var currentPosition = parseInt(getTop());
	
	divItems.style.top = currentPosition + (0.2 * distance) + "px";
	
	var timer = setTimeout("moveUp(" + destination + ", " + (0.8 * distance + 1) +")", 1000/20);
	
	if (Math.abs(destination / currentPosition) >= 1 || currentPosition >= -5) { 
		clearTimeout(timer);
		divItems.style.top = destination + "px";
		isRunning = false;
	}
	
	checkButtons();
}

function nextBtn()
{
	divItems = document.getElementById("storyWrapper");
	var currentPosition = parseInt(getTop());
	
	if(Math.abs(currentPosition - itemHeight) < divItems.offsetHeight - 100 && isRunning == false) {
		if (Math.abs(currentPosition - containerHeight) < divItems.offsetHeight) {
			isRunning = true;
			moveDown((currentPosition - itemHeight), itemHeight);
		}
		else
		{
			isRunning = false;	
		}
	}
}

function moveDown(destination, distance)
{
	var divItems = document.getElementById("storyWrapper");

	var currentPosition = parseInt(getTop());

	divItems.style.top = currentPosition - (0.2 * distance) + "px";

	var timer = setTimeout("moveDown(" + destination + ", " + (0.8 * distance + 1) +")", 1000/20);

	if (Math.abs(destination / currentPosition) <= 1) {
		clearTimeout(timer);
		divItems.style.top = destination + "px";
		isRunning = false;
	}
	checkButtons();
}

function changePanel(currentItem)
{
    i = 1;
	
    do{
        document.getElementById("sliderButton" + i).className = "";
        document.getElementById("sliderContent" + i).style.display = "none";
        i++;
    } while(document.getElementById("sliderButton" + i));
	
    document.getElementById("sliderButton" + currentItem).className = "sliderActive";
    document.getElementById("sliderContent" + currentItem).style.display = "block";
}

// on load make the newsreel spin once
$(document).ready(function() 
{
     nextBtn();
     var timer = setTimeout("moveAgain()", 4000);
});

// on load move newsreel back to top
function moveAgain()
{
     previousBtn();
}