/**
 * @author Ryan Johnson <http://saucytiger.com/>
 * @copyright 2008 PersonalGrid Corporation <http://personalgrid.com/>
 * @package LivePipe UI
 * @license MIT
 * @url http://livepipe.net/control/scrollbar
 * @require prototype.js, slider.js, livepipe.js
 */

if(typeof(Prototype) == "undefined")
	throw "Control.ScrollBar requires Prototype to be loaded.";
if(typeof(Control.Slider) == "undefined")
	throw "Control.ScrollBar requires Control.Slider to be loaded.";
if(typeof(Object.Event) == "undefined")
	throw "Control.ScrollBar requires Object.Event to be loaded.";

Control.ScrollBar = Class.create({
	initialize: function(container,track,options){
		this.enabled = false;
		this.notificationTimeout = false;
		this.container = $(container);
		this.boundMouseWheelEvent = this.onMouseWheel.bindAsEventListener(this);
		this.boundResizeObserver = this.onWindowResize.bind(this);
		this.track = $(track);
		this.handle = this.track.firstDescendant();
		this.options = Object.extend({
			active_class_name: 'scrolling',
			apply_active_class_name_to: this.container,
			notification_timeout_length: 125,
			handle_minimum_height: 25,
			scroll_to_smoothing: 0.01,
			scroll_to_steps: 15,
			proportional: true,
			slider_options: {}
		},options || {});
		this.slider = new Control.Slider(this.handle,this.track,Object.extend({
			axis: 'vertical',
			onSlide: this.onChange.bind(this),
			onChange: this.onChange.bind(this)
		},this.options.slider_options));
		this.recalculateLayout();
		Event.observe(window,'resize',this.boundResizeObserver);
		this.handle.observe('mousedown',function(){
		    if(this.auto_sliding_executer)
    			this.auto_sliding_executer.stop();
		}.bind(this));
	},
	destroy: function(){
		Event.stopObserving(window,'resize',this.boundResizeObserver);
	},
	enable: function(){
		this.enabled = true;
		this.container.observe('mouse:wheel',this.boundMouseWheelEvent);
		this.slider.setEnabled();
		this.track.show();
		if(this.options.active_class_name)
			$(this.options.apply_active_class_name_to).addClassName(this.options.active_class_name);
		this.notify('enabled');
	},
	disable: function(){
		this.enabled = false;
		this.container.stopObserving('mouse:wheel',this.boundMouseWheelEvent);
		this.slider.setDisabled();
		this.track.hide();
		if(this.options.active_class_name)
			$(this.options.apply_active_class_name_to).removeClassName(this.options.active_class_name);
		this.notify('disabled');
		this.reset();
	},
	reset: function(){
		this.slider.setValue(0);
	},
	recalculateLayout: function(){
		if(this.container.scrollHeight <= this.container.offsetHeight)
			this.disable();
		else{
			this.slider.trackLength = this.slider.maximumOffset() - this.slider.minimumOffset();
			if(this.options.proportional){
				this.handle.style.height = Math.max(this.container.offsetHeight * (this.container.offsetHeight / this.container.scrollHeight),this.options.handle_minimum_height) + 'px';
				this.slider.handleLength = this.handle.style.height.replace(/px/,'');
			}
			this.enable();
		}
	},
	onWindowResize: function(){
		this.recalculateLayout();
		this.scrollBy(0);
	},
	onMouseWheel: function(event){
	    if(this.auto_sliding_executer)
			this.auto_sliding_executer.stop();
		this.slider.setValueBy(-(event.memo.delta / 20)); //put in math to account for the window height
		event.stop();
		return false;
	},
	onChange: function(value){
		this.container.scrollTop = Math.round(value / this.slider.maximum * (this.container.scrollHeight - this.container.offsetHeight));
		if(this.notification_timeout)
			window.clearTimeout(this.notificationTimeout);
		this.notificationTimeout = window.setTimeout(function(){
			this.notify('change',value);
		}.bind(this),this.options.notification_timeout_length);
	},
	getCurrentMaximumDelta: function(){
		return this.slider.maximum * (this.container.scrollHeight - this.container.offsetHeight);
	},
	getDeltaToElement: function(element){
		return this.slider.maximum * ((element.positionedOffset().top + (element.getHeight() / 2)) - (this.container.getHeight() / 2));
	},
	scrollTo: function(y,animate){
		var current_maximum_delta = this.getCurrentMaximumDelta();
		if(y == 'top')
			y = 0;
		else if(y == 'bottom')
			y = current_maximum_delta;
		else if(typeof(y) != "number")
			y = this.getDeltaToElement($(y));
		if(this.enabled){
			y = Math.max(0,Math.min(y,current_maximum_delta));
			if(this.auto_sliding_executer)
				this.auto_sliding_executer.stop();
			var target_value = y / current_maximum_delta;
			var original_slider_value = this.slider.value;
			var delta = (target_value - original_slider_value) * current_maximum_delta;
			if(animate){
				this.auto_sliding_executer = new PeriodicalExecuter(function(){
					if(Math.round(this.slider.value * 100) / 100 < Math.round(target_value * 100) / 100 || Math.round(this.slider.value * 100) / 100 > Math.round(target_value * 100) / 100){
						this.scrollBy(delta / this.options.scroll_to_steps);
					}else{
						this.auto_sliding_executer.stop();
						this.auto_sliding_executer = null;
						if(typeof(animate) == "function")
							animate();
					}			
				}.bind(this),this.options.scroll_to_smoothing);
			}else
				this.scrollBy(delta);
		}else if(typeof(animate) == "function")
			animate();
	},
	scrollBy: function(y){
		if(!this.enabled)
			return false;
		this.slider.setValueBy(y / this.getCurrentMaximumDelta());
	}
});
Object.Event.extend(Control.ScrollBar);