/*
	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
		
		
		http://www.jools.net/projectdocs/
		
	*/
	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.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 'makeScroll' and wrap them in a Scroller.
	 */
	Scroller.setAll = function () {
		$$('.makeScroll').each(function(item) {
			Scroller.ids[item.id] = new Scroller(item);
		});
	}
	
	/*
	function: Scroller.reset
		If the passed element has class 'makeScroll', wrap it in a Scroller.
	 */
	Scroller.reset = function (body_id) {
		if ($(body_id).className.match(new RegExp("(^|\\s)makeScroll(\\s|$)"))) {
		   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);