/* Copyright (c) 2006 Kelvin Luck (kelvin AT kelvinluck DOT com || http://www.kelvinluck.com)
* Dual licensed under the MIT (http://www.opensource.org/licenses/mit-license.php)
* and GPL (http://www.opensource.org/licenses/gpl-license.php) licenses.
*
* See http://kelvinluck.com/assets/jquery/jScrollPane/
* $Id: jScrollPane.js 4702 2008-02-09 10:19:47Z kelvin.luck $
*/

/**
* Replace the vertical scroll bars on any matched elements with a fancy
* styleable (via CSS) version. With JS disabled the elements will
* gracefully degrade to the browsers own implementation of overflow:auto.
* If the mousewheel plugin has been included on the page then the scrollable areas will also
* respond to the mouse wheel.
*
* @example jQuery(".scroll-pane").jScrollPane();
*
* @name jScrollPane
* @type jQuery
* @param Object	settings	hash with options, described below.
*								scrollbarWidth	-	The width of the generated scrollbar in pixels
*								scrollbarMargin	-	The amount of space to leave on the side of the scrollbar in pixels
*								wheelSpeed		-	The speed the pane will scroll in response to the mouse wheel in pixels
*								showArrows		-	Whether to display arrows for the user to scroll with
*								arrowSize		-	The height of the arrow buttons if showArrows=true
*								animateTo		-	Whether to animate when calling scrollTo and scrollBy
*								dragMinHeight	-	The minimum height to allow the drag bar to be
*								dragMaxHeight	-	The maximum height to allow the drag bar to be
*								animateInterval	-	The interval in milliseconds to update an animating scrollPane (default 100)
*								animateStep		-	The amount to divide the remaining scroll distance by when animating (default 3)
*								maintainPosition-	Whether you want the contents of the scroll pane to maintain it's position when you re-initialise it - so it doesn't scroll as you add more content (default true)
*								scrollbarOnLeft	-	Display the scrollbar on the left side?  (needs stylesheet changes, see examples.html)
* @return jQuery
* @cat Plugins/jScrollPane
* @author Kelvin Luck (kelvin AT kelvinluck DOT com || http://www.kelvinluck.com)
*/
jQuery.jScrollPane = {
	active : []
};
jQuery.fn.jScrollPane = function(settings)
{

	settings = jQuery.extend(
	{
		scrollbarWidth : 10,
		scrollbarMargin : 5,
		wheelSpeed : 18,
		showArrows : false,
		arrowSize : 0,
		animateTo : false,
		dragMinHeight : 1,
		dragMaxHeight : 99999,
		animateInterval : 100,
		animateStep: 3,
		maintainPosition: true,
		scrollbarOnLeft: false
	}, settings
	);
	return this.each(
	function()
	{
		var $this = jQuery(this);

		if (jQuery(this).parent().is('.jScrollPaneContainer')) {
			var currentScrollPosition = settings.maintainPosition ? $this.offset({relativeTo:jQuery(this).parent()[0]}).top : 0;
			var $c = jQuery(this).parent();
			var paneWidth = $c.innerWidth();
			var paneHeight = $c.outerHeight();
			var trackHeight = paneHeight;
			if ($c.unmousewheel) {
				$c.unmousewheel();
			}
			jQuery('>.jScrollPaneTrack, >.jScrollArrowUp, >.jScrollArrowDown', $c).remove();
			$this.css({'top':0});
		} else {
			var currentScrollPosition = 0;
			this.originalPadding = $this.css('paddingTop') + ' ' + $this.css('paddingRight') + ' ' + $this.css('paddingBottom') + ' ' + $this.css('paddingLeft');
			this.originalSidePaddingTotal = (parseInt($this.css('paddingLeft')) || 0) + (parseInt($this.css('paddingRight')) || 0);
			var paneWidth = $this.innerWidth();
			var paneHeight = $this.innerHeight();
			var trackHeight = paneHeight;
			$this.wrap(
			jQuery('<div></div>').attr(
			{'className':'jScrollPaneContainer'}
			).css(
			{
			'height':paneHeight+'px',
			'width':paneWidth+'px'
			}
			)
			);
			// deal with text size changes (if the jquery.em plugin is included)
			// and re-initialise the scrollPane so the track maintains the
			// correct size
			jQuery(document).bind(
			'emchange',
			function(e, cur, prev)
			{
				$this.jScrollPane(settings);
			}
			);
		}
		var p = this.originalSidePaddingTotal;

		var cssToApply = {
		'height':'auto',
		'width':paneWidth - settings.scrollbarWidth - settings.scrollbarMargin - p + 'px'
		}

		if(settings.scrollbarOnLeft) {
			cssToApply.paddingLeft = settings.scrollbarMargin + settings.scrollbarWidth + 'px';
		} else {
			cssToApply.paddingRight = settings.scrollbarMargin + 'px';
		}

		$this.css(cssToApply);

		var contentHeight = $this.outerHeight();
		var percentInView = paneHeight / contentHeight;

		if (percentInView < .99) {
			var $container = $this.parent();
			$container.append(
			jQuery('<div></div>').attr({'className':'jScrollPaneTrack'}).css({'width':settings.scrollbarWidth+'px'}).append(
			jQuery('<div></div>').attr({'className':'jScrollPaneDrag'}).css({'width':settings.scrollbarWidth+'px'}).append(
			jQuery('<div></div>').attr({'className':'jScrollPaneDragTop'}).css({'width':settings.scrollbarWidth+'px'}),
			jQuery('<div></div>').attr({'className':'jScrollPaneDragBottom'}).css({'width':settings.scrollbarWidth+'px'})
			)
			)
			);

			var $track = jQuery('>.jScrollPaneTrack', $container);
			var $drag = jQuery('>.jScrollPaneTrack .jScrollPaneDrag', $container);

			if (settings.showArrows) {

				var currentArrowButton;
				var currentArrowDirection;
				var currentArrowInterval;
				var currentArrowInc;
				var whileArrowButtonDown = function()
				{
					if (currentArrowInc > 4 || currentArrowInc%4==0) {
						positionDrag(dragPosition + currentArrowDirection * mouseWheelMultiplier);
					}
					currentArrowInc ++;
				};
				var onArrowMouseUp = function(event)
				{
					jQuery('html').unbind('mouseup', onArrowMouseUp);
					currentArrowButton.removeClass('jScrollActiveArrowButton');
					clearInterval(currentArrowInterval);
					//console.log($(event.target));
					//currentArrowButton.parent().removeClass('jScrollArrowUpClicked jScrollArrowDownClicked');
				};
				var onArrowMouseDown = function() {
					//console.log(direction);
					//currentArrowButton = $(this);
					jQuery('html').bind('mouseup', onArrowMouseUp);
					currentArrowButton.addClass('jScrollActiveArrowButton');
					currentArrowInc = 0;
					whileArrowButtonDown();
					currentArrowInterval = setInterval(whileArrowButtonDown, 100);
				};
				$container
				.append(
				jQuery('<a></a>')
				.attr({'href':'javascript:;', 'className':'jScrollArrowUp'})
				.css({'width':settings.scrollbarWidth+'px'})
				.html('Scroll up')
				.bind('mousedown', function()
				{
					currentArrowButton = jQuery(this);
					currentArrowDirection = -1;
					onArrowMouseDown();
					this.blur();
					return false;
				}),
				jQuery('<a></a>')
				.attr({'href':'javascript:;', 'className':'jScrollArrowDown'})
				.css({'width':settings.scrollbarWidth+'px'})
				.html('Scroll down')
				.bind('mousedown', function()
				{
					currentArrowButton = jQuery(this);
					currentArrowDirection = 1;
					onArrowMouseDown();
					this.blur();
					return false;
				})
				);
				var $upArrow = jQuery('>.jScrollArrowUp', $container);
				var $downArrow = jQuery('>.jScrollArrowDown', $container);
				if (settings.arrowSize) {
					trackHeight = paneHeight - settings.arrowSize - settings.arrowSize;
					$track
					.css({'height': trackHeight+'px', top:settings.arrowSize+'px'})
				} else {
					var topArrowHeight = $upArrow.height();
					settings.arrowSize = topArrowHeight;
					trackHeight = paneHeight - topArrowHeight - $downArrow.height();
					$track
					.css({'height': trackHeight+'px', top:topArrowHeight+'px'})
				}
			}

			var $pane = jQuery(this).css({'position':'absolute', 'overflow':'visible'});

			var currentOffset;
			var maxY;
			var mouseWheelMultiplier;
			// store this in a seperate variable so we can keep track more accurately than just updating the css property..
			var dragPosition = 0;
			var dragMiddle = percentInView*paneHeight/2;

			// pos function borrowed from tooltip plugin and adapted...
			var getPos = function (event, c) {
				var p = c == 'X' ? 'Left' : 'Top';
				return event['page' + c] || (event['client' + c] + (document.documentElement['scroll' + p] || document.body['scroll' + p])) || 0;
			};

			var ignoreNativeDrag = function() {	return false; };

			var initDrag = function()
			{
				ceaseAnimation();
				currentOffset = $drag.offset(false);
				currentOffset.top -= dragPosition;
				maxY = trackHeight - $drag[0].offsetHeight;
				mouseWheelMultiplier = 2 * settings.wheelSpeed * maxY / contentHeight;
			};

			var onStartDrag = function(event)
			{
				initDrag();
				dragMiddle = getPos(event, 'Y') - dragPosition - currentOffset.top;
				jQuery('html').bind('mouseup', onStopDrag).bind('mousemove', updateScroll);
				if (jQuery.browser.msie) {
					jQuery('html').bind('dragstart', ignoreNativeDrag).bind('selectstart', ignoreNativeDrag);
				}
				return false;
			};
			var onStopDrag = function()
			{
				jQuery('html').unbind('mouseup', onStopDrag).unbind('mousemove', updateScroll);
				dragMiddle = percentInView*paneHeight/2;
				if (jQuery.browser.msie) {
					jQuery('html').unbind('dragstart', ignoreNativeDrag).unbind('selectstart', ignoreNativeDrag);
				}
			};
			var positionDrag = function(destY)
			{
				destY = destY < 0 ? 0 : (destY > maxY ? maxY : destY);
				dragPosition = destY;
				$drag.css({'top':destY+'px'});
				var p = destY / maxY;
				$pane.css({'top':((paneHeight-contentHeight)*p) + 'px'});
				$this.trigger('scroll');
				if (settings.showArrows) {
					$upArrow[destY == 0 ? 'addClass' : 'removeClass']('disabled');
					$downArrow[destY == maxY ? 'addClass' : 'removeClass']('disabled');
				}
			};
			var updateScroll = function(e)
			{
				positionDrag(getPos(e, 'Y') - currentOffset.top - dragMiddle);
			};

			var dragH = Math.max(Math.min(percentInView*(paneHeight-settings.arrowSize*2), settings.dragMaxHeight), settings.dragMinHeight);

			$drag.css(
			{'height':dragH+'px'}
			).bind('mousedown', onStartDrag);

			var trackScrollInterval;
			var trackScrollInc;
			var trackScrollMousePos;
			var doTrackScroll = function()
			{
				if (trackScrollInc > 8 || trackScrollInc%4==0) {
					positionDrag((dragPosition - ((dragPosition - trackScrollMousePos) / 2)));
				}
				trackScrollInc ++;
			};
			var onStopTrackClick = function()
			{
				clearInterval(trackScrollInterval);
				jQuery('html').unbind('mouseup', onStopTrackClick).unbind('mousemove', onTrackMouseMove);
			};
			var onTrackMouseMove = function(event)
			{
				trackScrollMousePos = getPos(event, 'Y') - currentOffset.top - dragMiddle;
			};
			var onTrackClick = function(event)
			{
				initDrag();
				onTrackMouseMove(event);
				trackScrollInc = 0;
				jQuery('html').bind('mouseup', onStopTrackClick).bind('mousemove', onTrackMouseMove);
				trackScrollInterval = setInterval(doTrackScroll, 100);
				doTrackScroll();
			};

			$track.bind('mousedown', onTrackClick);

			// if the mousewheel plugin has been included then also react to the mousewheel
			if ($container.mousewheel) {
				$container.mousewheel(
				function (event, delta) {
					initDrag();
					ceaseAnimation();
					var d = dragPosition;
					positionDrag(dragPosition - delta * mouseWheelMultiplier);
					var dragOccured = d != dragPosition;
					return !dragOccured;
				},
				false
				);
			}
			var _animateToPosition;
			var _animateToInterval;
			function animateToPosition()
			{
				var diff = (_animateToPosition - dragPosition) / settings.animateStep;
				if (diff > 1 || diff < -1) {
					positionDrag(dragPosition + diff);
				} else {
					positionDrag(_animateToPosition);
					ceaseAnimation();
				}
			}
			var ceaseAnimation = function()
			{
				if (_animateToInterval) {
					clearInterval(_animateToInterval);
					delete _animateToPosition;
				}
			};
			var scrollTo = function(pos, preventAni)
			{
				if (typeof pos == "string") {
					$e = jQuery(pos, this);
					if (!$e.length) return;
					pos = $e.offset().top - $this.offset().top;
				}
				ceaseAnimation();
				var destDragPosition = -pos/(paneHeight-contentHeight) * maxY;
				if (!preventAni || settings.animateTo) {
					_animateToPosition = destDragPosition;
					_animateToInterval = setInterval(animateToPosition, settings.animateInterval);
				} else {
					positionDrag(destDragPosition);
				}
			};
			$this[0].scrollTo = scrollTo;

			$this[0].scrollBy = function(delta)
			{
				var currentPos = -parseInt($pane.css('top')) || 0;
				scrollTo(currentPos + delta);
			};

			initDrag();

			scrollTo(-currentScrollPosition, true);

			jQuery.jScrollPane.active.push($this[0]);

		} else {
			$this.css(
			{
			'height':paneHeight+'px',
			'width':paneWidth-this.originalSidePaddingTotal+'px',
			'padding':this.originalPadding
			}
			);
			// remove from active list?
		}

	}
	)
};

// clean up the scrollTo expandos
jQuery(window)
.bind('unload', function() {
	var els = jQuery.jScrollPane.active;
	for (var i=0; i<els.length; i++) {
		els[i].scrollTo = els[i].scrollBy = null;
	}
}
);