//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, isCenter) {
        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);
                if (isCenter && (typeof(isCenter) != 'undefined')) {
                    this._yTrack  = this._findComponent("Scrollbar-TrackC", this._parent);
                } else {
                    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";
                        this._up.style.visibility = "hidden";
                        this._down.style.visibility = "hidden";
                        this._yTrack.style.visibility = "hidden";
                        if (this.auto) this._parent.style.visibility = "hidden";
                } else {
                        this._disabled = false;
                        this._yHandle.style.visibility = "inherit";
                        this._up.style.visibility = "inherit";
                        this._down.style.visibility = "inherit";
                        this._yTrack.style.visibility = "inherit";
                        this._parent.style.visibility  = "inherit";
                }
        };
        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];
                        }
                }
                //alert(c + ' in ' + o + '(' + o.id + ')' + ' not found');
        };
        //Thank you, Quirksmode
        function findOffsetTop (o) {
                var t = 0;
                if (o.offsetParent) {
                        while (o.offsetParent) {
                                t += o.offsetTop;
                                o  = o.offsetParent;
                        }
                }

                //alert(t);
                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);
                self._addEvent(document, "mouseout", self._stopScroll, false);

                return false;
        };
        this._scrollbarDrag = function (e) {
                self._removeEvent(document, "mouseout", self._stopScroll, false);
                e = e ? e : event;
                var t = parseInt(self._yHandle.style.top);
                var v = e.clientY + document.documentElement.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.documentElement.scrollTop;
                this._scroll(0, curY - this._trackTop - this._handleHeight/2);
        };
        this._scrollHandle = function (e) {
                var curY = e.clientY + document.documentElement.scrollTop;
                this._trackTop = findOffsetTop(this._yTrack);
                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();
};