var dom = document.getElementById;
var iex = document.all;
var ns4 = document.layers;
var mouseX, mouseY, enterX, enterY;


function addEvent(event,method)
{
	this[event] = method;
	if(ns4) this.captureEvents(Event[event.substr(2,event.length).toUpperCase()]);
}

function removeEvent(event)
{
	this[event] = null;
	if(ns4) this.releaseEvents(Event[event.substr(2,event.length).toUpperCase()]);
}

function getElement(name)
{
	var el = dom ? document.getElementById(name) : iex ? document.all[name] : ns4 ? eval("document."+name) : false;
	if ( el == null ) return null;
	el.css = ns4 ? el : el.style;
	el.getTop = function(){return parseInt(el.css.top) || 0};
	el.setTop = function(y){el.css.top = ns4 ? y: y+"px"};
	el.getLeft = function(){return parseInt(el.css.left) || 0};
	el.setLeft = function(x){el.css.left = ns4 ? x: x+"px"};
	el.getHeight = function(){return ns4 ? el.document.height : el.offsetHeight};
	el.getWidth = function(){return ns4 ? el.document.width : el.offsetWidth};
	el.getClipHeight = function(){return ns4 ? el.clip.height : el.offsetHeight};
	el.hideVis = function(){el.css.visibility="hidden"};
	el.showVis = function(){el.css.visibility="visible"};
	el.addEvent = addEvent;
	el.removeEvent = removeEvent;
	return el;
}

function getYMouse(e)
{
	return iex ? event.clientY : e.pageY;
}

document.addEvent = addEvent;
document.removeEvent = removeEvent;

ScrollObj = function(speed, groupName)
{
	this.speed = speed;
	this.trackObj = getElement(groupName+"ScrollTrack");
	this.dragObj = getElement(groupName+"ScrollThumb");
	this.contentMaskObj = getElement(groupName+"ContentClip");
	this.contentObj = getElement(groupName+"Content");
	this.obj = groupName+"ContentObject";
	eval(this.obj+"=this");
	
	this.dragHeight = this.dragObj.getHeight()-2 - (iex ? 4 : 0);
	this.trackHeight = getElement(groupName+"ScrollThumbTrack").getHeight();
	this.trackTop = this.trackObj.getTop();
	this.trackLength = this.trackHeight-this.dragHeight;
	this.trackBottom = this.trackTop+this.trackLength;
	this.contentMaskHeight = this.contentMaskObj.getClipHeight();
	this.contentHeight = this.contentObj.getHeight();
	this.contentLength = this.contentHeight-this.contentMaskHeight;
	this.scrollLength = this.trackLength/this.contentLength;
	this.scrollTimer = null;
	
	if (this.contentHeight <= this.contentMaskHeight) {
		this.dragObj.hideVis();
	} else {
		var self = this;
		this.dragObj.addEvent("onmousedown", function(e){self.startDrag(e);return false});
		if(iex) this.dragObj.addEvent("ondragstart", function(){return false});
		this.dragObj.showVis();
	}
}

ScrollObj.prototype.startDrag = function(e)
{
	this.dragStartMouse = getYMouse(e);
	this.dragStartOffset = this.dragObj.getTop();
	var self = this;
	document.removeEvent("onmousemove");
	document.addEvent("onmousemove", function(e){self.drag(e)});
	document.addEvent("onmouseup", function(){self.stopDrag()});
}

ScrollObj.prototype.stopDrag = function() 
{
	document.removeEvent("onmousemove");
	document.addEvent("onmousemove", getYMouse);
	document.removeEvent("onmouseup");
}

ScrollObj.prototype.drag = function(e)
{
	var currentMouse = getYMouse(e);
	var mouseDifference = currentMouse-this.dragStartMouse;
	var dragDistance = this.dragStartOffset+mouseDifference;
	var dragMovement = (dragDistance<this.trackTop) ? this.trackTop : (dragDistance>this.trackBottom) ? this.trackBottom : dragDistance;
	this.dragObj.setTop(dragMovement);
	var contentMovement = -(dragMovement-this.trackTop)*(1/this.scrollLength);
	this.contentObj.setTop(contentMovement);
}

ScrollObj.prototype.scroll = function(speed)
{
	var contentMovement = this.contentObj.getTop()+speed;
	var dragMovement = this.trackTop-Math.round(this.contentObj.getTop()*(this.trackLength/this.contentLength));
	if(contentMovement > 0){
		contentMovement = 0;
	}else if(contentMovement < -this.contentLength){
		contentMovement = -this.contentLength;
	}
	if ( dragMovement < this.trackTop ) {
		dragMovement = this.trackTop;
	} else if ( dragMovement > this.trackBottom ) {
		dragMovement = this.trackBottom;
	}
	this.contentObj.setTop(contentMovement);
	this.dragObj.setTop(dragMovement);
	this.scrollTimer = window.setTimeout(this.obj+".scroll("+speed+")",25);
}

ScrollObj.prototype.stopScroll = function()
{
	if(this.scrollTimer){
		window.clearTimeout(this.scrollTimer);
		this.scrollTimer = null;
	}
}

ScrollObj.prototype.scrollJump = function(e)
{
	var currentMouse = getYMouse(e);
	var dragDistance = currentMouse-(this.dragHeight/2);
	var dragMovement = (dragDistance<this.trackTop) ? this.trackTop : (dragDistance>this.trackBottom) ? this.trackBottom : dragDistance;
	this.dragObj.setTop(dragMovement);
	var contentMovement = -(dragMovement-this.trackTop)*(1/this.scrollLength);
	this.contentObj.setTop(contentMovement);
}

ScrollObj.prototype.scrollToTop = function()
{
	this.dragObj.setTop(0);
	this.contentObj.setTop(0);
}