/**
* @author Ryan Johnson <http://syntacticx.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)
			$(this.options.apply_active_class_name_to).removeClassName(this.options.active_class_name);
		this.notify('disabled');
		this.reset();
	},
	reset: function() {
		this.slider.setValue(0);
	},
	recalculateLayout: function() {
		if (this.container.scrollHeight <= this.container.offsetHeight)
			this.disable();
		else {
			this.enable();
			this.slider.trackLength = this.slider.maximumOffset() - this.slider.minimumOffset();
			if (this.options.proportional) {
				this.handle.style.height = Math.max(this.container.offsetHeight * (this.container.offsetHeight / this.container.scrollHeight), this.options.handle_minimum_height) + 'px';
				this.slider.handleLength = this.handle.style.height.replace(/px/, '');
			}
		}
	},
	onWindowResize: function() {
		this.recalculateLayout();
		this.scrollBy(0);
	},
	onMouseWheel: function(event) {
		if (this.auto_sliding_executer)
			this.auto_sliding_executer.stop();
		this.slider.setValueBy(-(event.memo.delta / 20)); //put in math to account for the window height
		event.stop();
		return false;
	},
	onChange: function(value) {
		this.container.scrollTop = Math.round(value / this.slider.maximum * (this.container.scrollHeight - this.container.offsetHeight));
		if (this.notification_timeout)
			window.clearTimeout(this.notificationTimeout);
		this.notificationTimeout = window.setTimeout(function() {
			this.notify('change', value);
		} .bind(this), this.options.notification_timeout_length);
	},
	getCurrentMaximumDelta: function() {
		return this.slider.maximum * (this.container.scrollHeight - this.container.offsetHeight);
	},
	getDeltaToElement: function(element) {
		return this.slider.maximum * ((element.positionedOffset().top + (element.getHeight() / 2)) - (this.container.getHeight() / 2));
	},
	scrollTo: function(y, animate) {
		var current_maximum_delta = this.getCurrentMaximumDelta();
		if (y == 'top')
			y = 0;
		else if (y == 'bottom')
			y = current_maximum_delta;
		else if (typeof (y) != "number")
			y = this.getDeltaToElement($(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);