/* 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 33 2008-12-10 22:55:28Z 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)
 *								reinitialiseOnImageLoad - Whether the jScrollPane should automatically re-initialise itself when any contained images are loaded
 * @return jQuery
 * @cat Plugins/jScrollPane
 * @author Kelvin Luck (kelvin AT kelvinluck DOT com || http://www.kelvinluck.com)
 */


{
	var $ = jQuery;


	(function($) {

	$.jScrollPane = {
		active : []
	};
	$.fn.jScrollPane = function(settings)
	{
		settings = $.extend({}, $.fn.jScrollPane.defaults, settings);

		var rf = function() { return false; };
	
		return this.each(
			function()
			{
				var $this = $(this);
				// Switch the element's overflow to hidden to ensure we get the size of the element without the scrollbars [http://plugins.jquery.com/node/1208]
				$this.css('overflow', 'hidden');
				var paneEle = this;
			
				if ($(this).parent().is('.jScrollPaneContainer')) {
					var currentScrollPosition = settings.maintainPosition ? $this.position().top : 0;
					var $c = $(this).parent();
					var paneWidth = $c.innerWidth();
					var paneHeight = $c.outerHeight();
					var trackHeight = paneHeight;
					$('>.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()+22;
					var paneHeight = $this.innerHeight();
					var trackHeight = paneHeight;
					$this.wrap(
						$('<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
					$(document).bind(
						'emchange', 
						function(e, cur, prev)
						{
							$this.jScrollPane(settings);
						}
					);
				
				}
			
				if (settings.reinitialiseOnImageLoad) {
					// code inspired by jquery.onImagesLoad: http://plugins.jquery.com/project/onImagesLoad
					// except we re-initialise the scroll pane when each image loads so that the scroll pane is always up to size...
					// TODO: Do I even need to store it in $.data? Is a local variable here the same since I don't pass the reinitialiseOnImageLoad when I re-initialise?
					var $imagesToLoad = $.data(paneEle, 'jScrollPaneImagesToLoad') || $('img', $this);
					var loadedImages = [];
				
					if ($imagesToLoad.length) {
						$imagesToLoad.each(function(i, val)	{
							$(this).bind('load', function() {
								if($.inArray(i, loadedImages) == -1){ //don't double count images
									loadedImages.push(val); //keep a record of images we've seen
									$imagesToLoad = $.grep($imagesToLoad, function(n, i) {
										return n != val;
									});
									$.data(paneEle, 'jScrollPaneImagesToLoad', $imagesToLoad);
									settings.reinitialiseOnImageLoad = false;
									$this.jScrollPane(settings); // re-initialise
								}
							}).each(function(i, val) {
								if(this.complete || this.complete===undefined) { 
									//needed for potential cached images
									this.src = this.src; 
								} 
							});
						});
					};
				}

				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(
						$('<div></div>').attr({'className':'jScrollPaneTrack'}).css({'width':settings.scrollbarWidth+'px'}).append(
							$('<div></div>').attr({'className':'jScrollPaneDrag'}).css({'width':settings.scrollbarWidth+'px'}).append(
								$('<div></div>').attr({'className':'jScrollPaneDragTop'}).css({'width':settings.scrollbarWidth+'px'}),
								$('<div></div>').attr({'className':'jScrollPaneDragBottom'}).css({'width':settings.scrollbarWidth+'px'})
							)
						)
					);
				
					var $track = $('>.jScrollPaneTrack', $container);
					var $drag = $('>.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)
						{
							$('html').unbind('mouseup', onArrowMouseUp);
							currentArrowButton.removeClass('jScrollActiveArrowButton');
							clearInterval(currentArrowInterval);
						};
						var onArrowMouseDown = function() {
							$('html').bind('mouseup', onArrowMouseUp);
							currentArrowButton.addClass('jScrollActiveArrowButton');
							currentArrowInc = 0;
							whileArrowButtonDown();
							currentArrowInterval = setInterval(whileArrowButtonDown, 100);
						};
						$container
							.append(
								$('<a></a>')
									.attr({'href':'javascript:;', 'className':'jScrollArrowUp'})
									.css({'width':settings.scrollbarWidth+'px'})
									.html('Scroll up')
									.bind('mousedown', function()
									{
										currentArrowButton = $(this);
										currentArrowDirection = -1;
										onArrowMouseDown();
										this.blur();
										return false;
									})
									.bind('click', rf),
								$('<a></a>')
									.attr({'href':'javascript:;', 'className':'jScrollArrowDown'})
									.css({'width':settings.scrollbarWidth+'px'})
									.html('Scroll down')
									.bind('mousedown', function()
									{
										currentArrowButton = $(this);
										currentArrowDirection = 1;
										onArrowMouseDown();
										this.blur();
										return false;
									})
									.bind('click', rf)
							);
						var $upArrow = $('>.jScrollArrowUp', $container);
						var $downArrow = $('>.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 = $(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;
						$('html').bind('mouseup', onStopDrag).bind('mousemove', updateScroll);
						if ($.browser.msie) {
							$('html').bind('dragstart', ignoreNativeDrag).bind('selectstart', ignoreNativeDrag);
						}
						return false;
					};
					var onStopDrag = function()
					{
						$('html').unbind('mouseup', onStopDrag).unbind('mousemove', updateScroll);
						dragMiddle = percentInView*paneHeight/2;
						if ($.browser.msie) {
							$('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);
						$('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;
						$('html').bind('mouseup', onStopTrackClick).bind('mousemove', onTrackMouseMove);
						trackScrollInterval = setInterval(doTrackScroll, 100);
						doTrackScroll();
					};
				
					$track.bind('mousedown', onTrackClick);
				
					$container.bind(
						'mousewheel',
						function (event, delta) {
							initDrag();
							ceaseAnimation();
							var d = dragPosition;
							positionDrag(dragPosition - delta * mouseWheelMultiplier);
							var dragOccured = d != dragPosition;
							return !dragOccured;
						}
					);

					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 = $(pos, $this);
							if (!$e.length) return;
							pos = $e.offset().top - $this.offset().top;
						}
						$container.scrollTop(0);
						ceaseAnimation();
						var destDragPosition = -pos/(paneHeight-contentHeight) * maxY;
						if (preventAni || !settings.animateTo) {
							positionDrag(destDragPosition);
						} else {
							_animateToPosition = destDragPosition;
							_animateToInterval = setInterval(animateToPosition, settings.animateInterval);
						}
					};
					$this[0].scrollTo = scrollTo;
				
					$this[0].scrollBy = function(delta)
					{
						var currentPos = -parseInt($pane.css('top')) || 0;
						scrollTo(currentPos + delta);
					};
				
					initDrag();
				
					scrollTo(-currentScrollPosition, true);
			
					// Deal with it when the user tabs to a link or form element within this scrollpane
					$('*', this).bind(
						'focus',
						function(event)
						{
							var $e = $(this);
						
							// loop through parents adding the offset top of any elements that are relatively positioned between
							// the focused element and the jScrollPaneContainer so we can get the true distance from the top
							// of the focused element to the top of the scrollpane...
							var eleTop = 0;
						
							while ($e[0] != $this[0]) {
								eleTop += $e.position().top;
								$e = $e.offsetParent();
							}
						
							var viewportTop = -parseInt($pane.css('top')) || 0;
							var maxVisibleEleTop = viewportTop + paneHeight;
							var eleInView = eleTop > viewportTop && eleTop < maxVisibleEleTop;
							if (!eleInView) {
								var destPos = eleTop - settings.scrollbarMargin;
								if (eleTop > viewportTop) { // element is below viewport - scroll so it is at bottom.
									destPos += $(this).height() + 15 + settings.scrollbarMargin - paneHeight;
								}
								scrollTo(destPos);
							}
						}
					)
				
				
					if (location.hash) {
						scrollTo(location.hash);
					}
				
					// use event delegation to listen for all clicks on links and hijack them if they are links to
					// anchors within our content...
					$(document).bind(
						'click',
						function(e)
						{
							$target = $(e.target);
							if ($target.is('a')) {
								var h = $target.attr('href');
								if (h.substr(0, 1) == '#') {
									scrollTo(h);
								}
							}
						}
					);
				
					$.jScrollPane.active.push($this[0]);
				
				} else {
					$this.css(
						{
							'height':paneHeight+'px',
							'width':paneWidth-this.originalSidePaddingTotal+'px',
							'padding':this.originalPadding
						}
					);
					// remove from active list?
					$this.parent().unbind('mousewheel');
				}
			
			}
		)
	};

	$.fn.jScrollPane.defaults = {
		scrollbarWidth : 10,
		scrollbarMargin : 5,
		wheelSpeed : 18,
		showArrows : false,
		arrowSize : 0,
		animateTo : false,
		dragMinHeight : 1,
		dragMaxHeight : 99999,
		animateInterval : 100,
		animateStep: 3,
		maintainPosition: true,
		scrollbarOnLeft: false,
		reinitialiseOnImageLoad: false
	};

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

	})(jQuery);

}