/* 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	-	在像素宽度所产生的滚动
 *								scrollbarMargin	-	离开滚动条的一侧，以像素为单位的空间量
 *								wheelSpeed		-	以像素为单位，该小组将在滚动鼠标滚轮的速度
 *								showArrows		-	是否为用户显示的箭头滚动
 *								arrowSize		-	上下箭头中间滚动条距顶部高度，如果showArrows= TRUE
 *								animateTo		-	当动画时调用scrollTo和scrollBy
 *								dragMinHeight	-	允许拖动栏的最小高度
 *								dragMaxHeight	-	允许拖动栏的最大高度
 *								animateInterval	-	以毫秒为单位的时间间隔来更新动画的JScrollPane（默认为100）
 *								animateStep		-	动画过程滚动距离（默认3）
 *								maintainPosition-	无论你想滚动窗格中的内容，以保持它的立场，当你重新初始化它 - 所以它不会滚动，当您添加更多的内容（默认为true）
 *								scrollbarOnLeft	-	显示在左边的滚动条？ （需要样式表的变化，看到examples.html）
 *								reinitialiseOnImageLoad - 当JScrollPane中应自动重新初始化本身包含的任何图像加载时
 * @return jQuery
 * @cat Plugins/jScrollPane
 * @author Kelvin Luck (kelvin AT kelvinluck DOT com || http://www.kelvinluck.com)
 */

(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();
				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);