/* 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)
 */

(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();
                
                var $drag = $('<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 = $('<div></div>').attr({'className':'jScrollPaneTrack'}).css({'width':settings.scrollbarWidth+'px'}).append($drag);
                $container.after($track );


                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
                        .after(
                            $('<a></a>')
                                .attr({'href':'javascript:;', 'className':'jScrollArrowUp', 'title' : 'Scroll Up'})
                                .css({'width':settings.scrollbarWidth+'px'})
                                .html('▲')
                                .bind('mousedown', function()
                                {
                                    currentArrowButton = $(this);
                                    currentArrowDirection = -1;
                                    onArrowMouseDown();
                                    this.blur();
                                    return false;
                                })
                                .bind('click', rf),
                            $('<a></a>')
                                .attr({'href':'javascript:;', 'className':'jScrollArrowDown', 'title' : 'Scroll Down'})
                                .css({'width':settings.scrollbarWidth+'px'})
                                .html('▼')
                                .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 - (settings.trackPadding*2);
                        $track
                            .css({'height': trackHeight+'px', top:(settings.arrowSize + settings.trackPadding)+'px'})
                    } else {
                        var topArrowHeight = $upArrow.height();
                        settings.arrowSize = topArrowHeight;
                        trackHeight = paneHeight - topArrowHeight - $downArrow.height() - (settings.trackPadding*2);
                        $track
                            .css({'height': trackHeight+'px', top:(topArrowHeight + settings.trackPadding)+'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,
    trackPadding: 0,
    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);