// Create scrolling variable if it doesn't exist
if (!Scrolling) var Scrolling = {};

//ScrollTween constructor
Scrolling.ScrollTween = function() {
	//private variables
	var self = this;
	var _steps = [0, 25, 50, 70, 85, 95, 97, 99, 100];
	var _values = [];
	var _idle = true;
	var o, _inc, _timer;

	//private functions
	function tweenTo(y) {
		if (!_idle) return false;

		var d = o.getDimensions();
		if (y < 0) y = 0;
		if (y > d.theight - d.vheight)
			y = d.theight - d.vheight;

		var dist = y - d.y;
		_inc = 0;
		_timer = null;
		_values = [];
		_idle = false;

		for (var i = 0; i < _steps.length; i++) {
			_values[i] = Math.round(d.y + dist * (_steps[i] / 100));
		}

		_timer = window.setInterval(function() {
			o.scrollTo(_values[_inc]);
			if (_inc == _steps.length - 1) {
				window.clearInterval(_timer);
				_idle = true;
			} else _inc++;
		}, o.stepSpeed);
	};

	function tweenBy(y) {
		o.tweenTo(o.getDimensions().y + y);
	};

	function setSteps(s) {
		_steps = s;
	};

	//public functions
	this.apply = function(p) {
		o = p;
		o.tweenTo = tweenTo;
		o.tweenBy = tweenBy;
		o.setSteps = setSteps;
		o.stepSpeed = 30;
	};
};