/* Copyright (c) 2009 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 90 2010-01-25 03:52:10Z 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)
 *								tabIndex		-	The tabindex for this jScrollPane to control when it is tabbed to when navigating via keyboard (default 0)
 *								enableKeyboardNavigation - Whether to allow keyboard scrolling of this jScrollPane when it is focused (default true)
 *								animateToInternalLinks - Whether the move to an internal link (e.g. when it's focused by tabbing or by a hash change in the URL) should be animated or instant (default false)
 *								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 (default false)
 *								topCapHeight	-	The height of the "cap" area between the top of the jScrollPane and the top of the track/ buttons
 *								bottomCapHeight	-	The height of the "cap" area between the bottom of the jScrollPane and the bottom of the track/ buttons
 *								observeHash		-	Whether jScrollPane should attempt to automagically scroll to the correct place when an anchor inside the scrollpane is linked to (default true)
 * @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 paneTop = $this.offset().top;
		        var paneLeft = $this.offset().left;
		        var pos = $this.offset();
		        var trackHeight = paneHeight;
		        $this.wrap(
					$('<div></div>').attr(
						{ 'className': 'jScrollPaneContainer' }
					).css(
						{
						    'height': paneHeight + 'px',
						    'width': paneWidth + 'px',
						    'top': pos.top + 'px',
						    'left': pos.left + 'px',
						    'position': 'Absolute'
						}
					)
				);
		        // 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', 'left': '0px' });

		    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);