/*

Class: Scroller

	Adds a scrollbar to a specific div. The scrollbar is implemented using a Script.aculo.us slider.

	The class reparents the original div, creates a slider and ties the reparented div to the slider,

	setting any properties necessary on the divs to make it all work. The scrollbar can be styled using

	CSS. The track of the scrollbar has class 'scroll-track', 'scroll-track-top' and 'scroll-track-bot',

	the thumb has class 'scroll-handle', 'scroll-handle-top' and 'scroll-handle-bot'.



properties:

	myIndex - an integer used to generate a unique ID for use in, for example, div ids.

	outerBox - the div that holds the scrollpane + scrollbar

	innerBox - the div that holds the scrollpane

	innerHeight - the height of the inner box.

	viewportHeight - the height of the view onto the scrolled div.

	track - a div that holds the script.aculo.us slider (the scrollbar)

	trackHeight - the height of the slider

	handle - the div for the 'thumb' of the scrollbar

	handleHeight - the height of the thumb

	slider - the script.aculo.us slider itself

	ieDecreaseBy - a fudge factor used when calculating the width of innerBox



*/

var Scroller = Class.create();



/*

property: Scroller.ids

	A cache of Scrollers indexed by the ID of the original div.

 */

Scroller.ids = new Object();



/*

property: Scroller.i

	A unique ID generator.

 */

Scroller.i = 0;



Scroller.prototype = {

	/*

	constructor: initialize

		Wrap the passed div in a scrollpane.



	parameters:

		el - the div to add a scrollbar to.

	 */

  initialize: function(el) {

    this.outerBox = el;

    this.decorate();

  },



  /*

  function: decorate

  	create the necessary elements to implement the scrollbar and wire up events.

   */

  decorate: function() {

	$(this.outerBox).makePositioned(); // Fix IE



	// Seed a unique ID

	Scroller.i = Scroller.i + 1;

	this.myIndex = Scroller.i;



	//wrap the existing content in an intermediate inner box

	this.innerBox = document.createElement("DIV");

	this.innerBox.className="scroll-innerBox";

	$(this.innerBox).makePositioned();	// Fix IE

	this.innerBox.style.cssFloat=this.innerBox.style.styleFloat='left';	// Need the scrollbar to appear next to the scrollpane

	this.innerBox.id="scroll-innerBox-"+Scroller.i;

	this.innerBox.style.top = "0px";



	//Transfer the contents of Outer Box to Inner Box

	while (this.outerBox.hasChildNodes()) {

		this.innerBox.appendChild(this.outerBox.firstChild);

	}

	this.innerBox.style.overflow="hidden";

	//turn off scrolling on the outer div

	this.outerBox.style.overflow="hidden";



	// create a track

	this.track=document.createElement('div');

	this.track.className="scroll-track";

	$(this.track).makePositioned();

	this.track.style.cssFloat=this.track.style.styleFloat='left';

	this.track.id="scroll-track-"+Scroller.i;

	// Fix IE line-height bug. Sigh.

	this.track.appendChild(document.createComment(''));



	// Create the top button

	this.tracktop=document.createElement('div');

	this.tracktop.className="scroll-track-top";

	$(this.tracktop).makePositioned();

	this.tracktop.style.cssFloat=this.tracktop.style.styleFloat='left';

	this.tracktop.id="scroll-track-top-"+Scroller.i;

	// Fix IE line-height bug. Sigh.

	this.tracktop.appendChild(document.createComment(''));



	// Create the bottom button

	this.trackbot=document.createElement('div');

	this.trackbot.className="scroll-track-bot";

	$(this.trackbot).makePositioned();

	this.trackbot.style.cssFloat=this.trackbot.style.styleFloat='left';

	this.trackbot.id="scroll-track-bot-"+Scroller.i;

	// Fix IE line-height bug. Sigh.

	this.trackbot.appendChild(document.createComment(''));



	// Create the handle

	this.handle=document.createElement('div');

	this.handle.className="scroll-handle-container";

	this.handle.id="scroll-handle-container"+Scroller.i;



	// Create the handle middle

	this.handle_middle=document.createElement('div');

	this.handle_middle.className="scroll-handle";

	$(this.handle_middle).makePositioned();

	this.handle_middle.id="scroll-handle-"+Scroller.i;

	// Fix IE line-height bug. Sigh.

	this.handle_middle.appendChild(document.createComment(''));



	// Create the handle top cap

	this.handletop=document.createElement('div');

	this.handletop.className="scroll-handle-top";

	$(this.handletop).makePositioned();

	this.handletop.id="scroll-handle-top-"+Scroller.i;

	// Fix IE line-height bug. Sigh.

	this.handletop.appendChild(document.createComment(''));



	// Create the handle bottom cap

	this.handlebot=document.createElement('div');

	this.handlebot.className="scroll-handle-bot";

	$(this.handlebot).makePositioned();

	this.handlebot.id="scroll-handle-bot-"+Scroller.i;

	// Fix IE line-height bug. Sigh.

	this.handlebot.appendChild(document.createComment(''));



	this.track.hide();

	this.tracktop.hide();

	this.trackbot.hide();



	this.outerBox.appendChild(this.innerBox);

	this.outerBox.appendChild(this.tracktop);

	this.handle.appendChild(this.handletop);

	this.handle.appendChild(this.handle_middle);

	this.handle.appendChild(this.handlebot);

	this.track.appendChild(this.handle);

	this.outerBox.appendChild(this.track);

	this.outerBox.appendChild(this.trackbot);



	this.slider = new Control.Slider($(this.handle).id, $(this.track).id, {axis:'vertical',

									 minimum: 0,

									 maximum: $(this.outerBox).clientHeight});

	this.slider.options.onSlide = this.slider.options.onChange = this.onChange.bind(this);

	setTimeout(this.resetScrollbar.bind(this, false), 10);



    this.domMouseCB = this.MouseWheelEvent.bindAsEventListener(this, this.slider);

    this.mouseWheelCB = this.MouseWheelEvent.bindAsEventListener(this, this.slider);

    this.trackTopCB = this.tracktopEvent.bindAsEventListener(this, this.slider);

    this.trackBotCB = this.trackbotEvent.bindAsEventListener(this, this.slider);



	//Events control

	$(this.outerBox).observe('DOMMouseScroll', this.domMouseCB); // Mozilla

	$(this.outerBox).observe('mousewheel', this.mouseWheelCB);// IE/Opera

	$(this.tracktop).observe('mousedown', this.trackTopCB);

	$(this.trackbot).observe('mousedown', this.trackBotCB);

  },



  release: function() {

    $(this.outerBox).stopObserving('DOMMouseScroll', this.domMouseCB);

	$(this.outerBox).stopObserving('mousewheel', this.mouseWheelCB);// IE/Opera

	$(this.tracktop).stopObserving('mousedown', this.trackTopCB);

	$(this.trackbot).stopObserving('mousedown', this.trackBotCB);

  },



  /*

  function: resetScrollbar

  	Re-calculate the geometry of the scrollbar. Typically called from an event handler.



	args:

		repeat - if true, set timer to re-calculate to fix IE bug on resize window.

   */

  resetScrollbar: function(repeat) {

		this.track.hide();

		this.tracktop.hide();

		this.trackbot.hide();

		this.enableScroll = false;

		this.innerHeight = $(this.outerBox).clientHeight;

		this.innerBox.style.height = this.innerHeight + "px";

		var newWidth = $(this.outerBox).clientWidth;



    	var tth = Element.getStyle(this.tracktop,"height");

    	if (tth)

    	   tth = tth.replace("px","");

    	else

    	   tth = 0;



        var hth = Element.getStyle(this.handletop,"height");

        if (hth)

    	   hth = hth.replace("px","");

    	else

    	   hth = 0;



		if (this.innerHeight < this.innerBox.scrollHeight) {

			this.viewportHeight = this.innerHeight - tth*2;

			this.slider.trackLength = this.viewportHeight;

			this.track.style.height = this.viewportHeight + "px";

/*			this.handleHeight = Math.round(this.viewportHeight * this.innerHeight / this.innerBox.scrollHeight);

			if(this.handleHeight < (hth*2))

				this.handleHeight = (hth*2);

			if (this.handleHeight < 10)

			     this.handleHeight = 10;*/

			this.handleHeight = 140;

			this.handle.style.height = this.handleHeight + "px";

			this.handle_middle.style.height = this.handleHeight - hth*2 + "px";

			this.handletop.style.height = hth + "px";

			this.slider.handleLength = this.handleHeight;

			this.track.style.display = 'inline';

			this.tracktop.style.display = 'inline';

			this.trackbot.style.display = 'inline';

			this.ieDecreaseBy = 1;   // Firefox seems to have an off-by one error, so allow for it.

			if (this.outerBox.currentStyle) {

				var borderWidth = this.outerBox.currentStyle["borderWidth"].replace("px","");

				if(!isNaN(borderWidth)) {

					this.ieDecreaseBy = (borderWidth) * 2;

				}

			}

			newWidth = ($(this.outerBox).clientWidth - $(this.track).clientWidth - this.ieDecreaseBy);

			this.enableScroll = true;

		}

		//Set the width of of the scrollpane (aka innerBox).

		this.innerBox.style.width = newWidth + "px";

		//Fix IE resize event Bug

		if(repeat) {

			setTimeout(this.resetScrollbar.bind(this, false), 10);

		}

  },



	//Mouse wheel code from http://adomas.org/javascript-mouse-wheel/

	MouseWheelEvent: function(event, slider) {

		var delta = 0;

		if (!event) //For IE.

			event = window.event;

		if (event.wheelDelta) { //IE/Opera.

			delta = event.wheelDelta / 120;

			/*if (window.opera) //In Opera 9, delta differs in sign as compared to IE

				delta = -delta;   But it isn't necessary with Opera v9.51*/

		} else if (event.detail) { //Mozilla case

			delta = -event.detail / 3;

		}

		if (delta)

			slider.setValueBy(-delta / 10);

		Event.stop(event);

	},



	trackbotEvent: function(event, slider) {

		if (Event.isLeftClick(event)) {

			slider.setValueBy(0.2);

			Event.stop(event);

		}

	},



	tracktopEvent: function(event, slider) {

		if (Event.isLeftClick(event)) {

			slider.setValueBy(-0.2);

			Event.stop(event);

		}

	},



  /*

  function: onChange

  	Called when the script.aculo.us slider has changed (i.e. when it has been dragged). Scroll the inner box.



	args:

		val - not used.

   */

	onChange: function(val) {

		if(this.enableScroll)

			this.innerBox.scrollTop = Math.round (val * (this.innerBox.scrollHeight-this.innerBox.offsetHeight));

	}

}



/*

function: Scroller.setAll

	Search for divs of the class 'overflow' and wrap them in a Scroller.

 */

Scroller.setAll = function () {

	$$('.overflow').each(function(item) {

		Scroller.ids[item.id] = new Scroller(item);

	});

}



/*

function: Scroller.reset

	If the passed element has class 'overflow', wrap it in a Scroller.

 */

Scroller.reset = function (body_id) {

	if ($(body_id).className.match(new RegExp("(^|\\s)overflow(\\s|$)"))) {

	   if (Scroller.ids[body_id])

	       Scroller.ids[body_id].release();



		Scroller.ids[body_id] = new Scroller($(body_id));

	}

}



/*

property: Scroller.updateAll

	Reset all of the scrollbars.

 */

Scroller.updateAll = function () {

	$H(Scroller.ids).each(function(pair) {

		Scroller.ids[pair.key].resetScrollbar(true);

	});

}



/*

	Hook up some global event handlers.

 */

Event.observe(window, "load", Scroller.setAll);

Event.observe(window, "resize", Scroller.updateAll);