//Written by Nathan Faubion: http://n-son.com
//Use this or edit how you want, just give me
//some credit!
function jsScrollbar (o, s, a, ev) {
	if(o != null){
		var self = this;
		
		this.reset = function () {
			//Arguments that were passed
			this._parent = o;
			this._src    = s;
			this.auto    = a ? a : false;
			this.eventHandler = ev ? ev : function () {};
			//Component Objects
			this._up   = this._findComponent("Scrollbar-Up", this._parent);
			this._down = this._findComponent("Scrollbar-Down", this._parent);
			this._yTrack  = this._findComponent("Scrollbar-Track", this._parent);
			this._yHandle = this._findComponent("Scrollbar-Handle", this._yTrack);
			//Height and position properties
			this._trackTop = findOffsetTop(this._yTrack);
			this._trackHeight  = this._yTrack.offsetHeight;
			this._handleHeight = this._yHandle.offsetHeight;
			this._x = 0;
			this._y = 0;
			//Misc. variables
			this._scrollDist  = 5;
			this._scrollTimer = null;
			this._selectFunc  = null;
			this._grabPoint   = null;
			this._tempTarget  = null;
			this._tempDistX   = 0;
			this._tempDistY   = 0;
			this._disabled    = false;
			this._ratio = (this._src.totalHeight - this._src.viewableHeight)/(this._trackHeight - this._handleHeight);
			
			this._yHandle.ondragstart  = function () {return false;};
			this._yHandle.onmousedown = function () {return false;};
			this._addEvent(this._src.content, "mousewheel", this._scrollbarWheel);
			this._removeEvent(this._parent, "mousedown", this._scrollbarClick);
			this._addEvent(this._parent, "mousedown", this._scrollbarClick);
			
			this._src.reset();
			with (this._yHandle.style) {
				top  = "0px";
				left = "0px";
			}
			this._moveContent();
			
			if (this._src.totalHeight < this._src.viewableHeight) {
				this._disabled = true;
				this._yHandle.style.visibility = "hidden";
				if (this.auto) this._parent.style.visibility = "hidden";
			} else {
				this._disabled = false;
				this._yHandle.style.visibility = "visible";
				this._parent.style.visibility  = "visible";
			}
		};
		this._addEvent = function (o, t, f) {
			if (o.addEventListener) o.addEventListener(t, f, false);
			else if (o.attachEvent) o.attachEvent('on'+ t, f);
			else o['on'+ t] = f;
		};
		this._removeEvent = function (o, t, f) {
			if (o.removeEventListener) o.removeEventListener(t, f, false);
			else if (o.detachEvent) o.detachEvent('on'+ t, f);
			else o['on'+ t] = null;
		};
		this._findComponent = function (c, o) {
			var kids = o.childNodes;
			for (var i = 0; i < kids.length; i++) {
				if (kids[i].className && kids[i].className == c) {
					return kids[i];
				}
			}
		};
		//Thank you, Quirksmode
		function findOffsetTop (o) {
			var t = 0;
			if (o.offsetParent) {
				while (o.offsetParent) {
					t += o.offsetTop;
					o  = o.offsetParent;
				}
			}
			return t;
		};
		this._scrollbarClick = function (e) {
			if (self._disabled) return false;
			
			e = e ? e : event;
			if (!e.target) e.target = e.srcElement;
			
			if (e.target.className.indexOf("Scrollbar-Up") > -1) self._scrollUp(e);
			else if (e.target.className.indexOf("Scrollbar-Down") > -1) self._scrollDown(e);
			else if (e.target.className.indexOf("Scrollbar-Track") > -1) self._scrollTrack(e);
			else if (e.target.className.indexOf("Scrollbar-Handle") > -1) self._scrollHandle(e);
			
			self._tempTarget = e.target;
			self._selectFunc = document.onselectstart;
			document.onselectstart = function () {return false;};
			
			self.eventHandler(e.target, "mousedown");
			self._addEvent(document, "mouseup", self._stopScroll, false);
			
			return false;
		};
		this._scrollbarDrag = function (e) {
			e = e ? e : event;
			var t = parseInt(self._yHandle.style.top);
			var v = e.clientY + document.body.scrollTop - self._trackTop;
			with (self._yHandle.style) {
				if (v >= self._trackHeight - self._handleHeight + self._grabPoint)
					top = self._trackHeight - self._handleHeight +"px";
				else if (v <= self._grabPoint) top = "0px";
				else top = v - self._grabPoint +"px";
				self._y = parseInt(top);
			}
			
			self._moveContent();
		};
		this._scrollbarWheel = function (e) {
			e = e ? e : event;
			var dir = 0;
			if (e.wheelDelta >= 120) dir = -1;
			if (e.wheelDelta <= -120) dir = 1;
			
			self.scrollBy(0, dir * 20);
			e.returnValue = false;
		};
		this._startScroll = function (x, y) {
			this._tempDistX = x;
			this._tempDistY = y;
			this._scrollTimer = window.setInterval(function () {
				self.scrollBy(self._tempDistX, self._tempDistY); 
			}, 40);
		};
		this._stopScroll = function () {
			self._removeEvent(document, "mousemove", self._scrollbarDrag, false);
			self._removeEvent(document, "mouseup", self._stopScroll, false);
			
			if (self._selectFunc) document.onselectstart = self._selectFunc;
			else document.onselectstart = function () { return true; };
			
			if (self._scrollTimer) window.clearInterval(self._scrollTimer);
			self.eventHandler (self._tempTarget, "mouseup");
		};
		this._scrollUp = function (e) {this._startScroll(0, -this._scrollDist);};
		this._scrollDown = function (e) {this._startScroll(0, this._scrollDist);};
		this._scrollTrack = function (e) {
			var curY = e.clientY + document.body.scrollTop;
			this._scroll(0, curY - this._trackTop - this._handleHeight/2);
		};
		this._scrollHandle = function (e) {
			var curY = e.clientY + document.body.scrollTop;
			this._grabPoint = curY - findOffsetTop(this._yHandle);
			this._addEvent(document, "mousemove", this._scrollbarDrag, false);
		};
		this._scroll = function (x, y) {
			if (y > this._trackHeight - this._handleHeight) 
				y = this._trackHeight - this._handleHeight;
			if (y < 0) y = 0;
			
			this._yHandle.style.top = y +"px";
			this._y = y;
			
			this._moveContent();
		};
		this._moveContent = function () {
			this._src.scrollTo(0, Math.round(this._y * this._ratio));
		};
		
		this.scrollBy = function (x, y) {
			this._scroll(0, (-this._src._y + y)/this._ratio);
		};
		this.scrollTo = function (x, y) {
			this._scroll(0, y/this._ratio);
		};
		this.swapContent = function (o, w, h) {
			this._removeEvent(this._src.content, "mousewheel", this._scrollbarWheel, false);
			this._src.swapContent(o, w, h);
			this.reset();
		};
		
		this.reset();
	}
};