/**@license boxplus: a lightweight pop-up window engine shipped with sigplus
 * @author  Levente Hunyadi
 * @version 1.4.2
 * @remarks Copyright (C) 2009-2010 Levente Hunyadi
 * @remarks Licensed under GNU/GPLv3, see http://www.gnu.org/licenses/gpl-3.0.html
 * @see     http://hunyadi.info.hu/projects/boxplus
 **/

/*
* boxplus: a lightweight pop-up window engine shipped with sigplus
* Copyright 2009-2010 Levente Hunyadi
*
* boxplus is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* boxplus is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with boxplus.  If not, see <http://www.gnu.org/licenses/>.
*/

if (typeof(__jQuery__) == 'undefined') {
	var __jQuery__ = jQuery;
}
(function ($) {
	// Settings
	var defaults = {
		rtl: false,
		theme: false,                  // theme to select when pop-up window opens; if set, style sheets that have a title attribute with a different ending will be disabled
		autofit: true,                 // whether to reduce oversized images to fit browser window when they are displayed [true|false]
		slideshow: 0,                  // time spent viewing an image when slideshow mode is active, or 0 to disable slideshow mode
		duration: 'slow',              // duration of animation sequences in milliseconds, or one of ['slow'|'fast']
		easing: 'swing',               // speed at which the animation progresses at different points within the change image/content animation ['swing'|'linear']
		loop: false,                   // whether the image/content sequence loops such that the first image/content follows the last [true|false]
		contextmenu: true,             // whether the context menu appears when right-clicking an image inside the pop-up window [true|false]
		thumbs: 'inside',              // placement of thumbnail navigation bar: over image or in caption area ['inside'|'outside']
		title: _getTitle,              // a two-argument function that returns the title text or node that belongs an anchor passed as a jQuery object
		description: _getDescription,  // a two-argument function that returns the description text or node that belongs to an anchor passed as a jQuery object
		download: _getDownloadUrl,     // a single-argument function that returns the download URL that belongs to an anchor passed as a jQuery object
		metadata: _getMetadata         // a single-argument function that returns arbirary HTML data that belongs to an anchor passed as a jQuery object
	},
	settings,

	// signature for settings.title and settings.description:
	// settings.description = function (anchor, sizing) {
	//    if (sizing) {
	//       // returned data is used only in calculating pop-up window dimensions
	//    } else {
	//       // returned data is to be displayed
	//    }
	// }

	// DOM elements
	background,          // partially shaded background
	dialog,              // lightweight pop-up window dialog
	dialogClone,         // a dialog clone for sizing
	dialogInitWidth,     // initial width for dialog, extracted from CSS
	dialogInitHeight,    // initial height for dialog, extracted from CSS
	dialogDefWidth,      // default width for dialog when there is no image to display, extracted from CSS
	dialogDefHeight,     // default height for dialog when there is no image to display, extracted from CSS
	viewer,              // image/content viewer inside dialog
	viewerimage,         // image in image/content viewer
	viewercontent,       // metadata/content in image/content viewer
	viewervideo,
	viewerflash,
	vieweritems,
	btnPrev,             // navigate to previous image/content button in dialog
	btnNext,             // navigate to next image/content button in dialog
	btnStart,            // start slideshow
	btnStop,             // stop slideshow
	btnClose,            // close window button in dialog
	btnDownload,         // download image/content button in dialog
	btnMetadata,         // metadata information button in dialog
	resizer,             // resize control
	shrink,
	thumbsBar,           // thumbnail bar for faster navigation
	thumbs,              // list of images on thumbnail bar
	btnScrollBack,       // scroll thumbnail bar backward control
	btnScrollForward,    // scroll thumbnail bar forward control
	caption,             // caption title and text below image/content
	panels,
	doc = $(document),
	body,

	// Image visualization
	preloader,           // image preloader or video dimensions placeholder
	anchors,             // array of HTML anchors to show in gallery
	current = -1,        // index of currently shown image/content in gallery
	progress = 0,        // progress indicator stage (used by _toggleProgress)
	thumbindex = -1,     // zero-based index of current thumbnail for thumbnail navigation bar slide mode (activated on mouse click), or -1 for scroll mode (activated on mouse hover)

	// Slideshow
	timer,

	// Right-to-left support
	rtl,
	rtlpos;

	// Constants
	/** @const */
	var BOXPLUS = 'boxplus';
	/** @const */
	var CLASS_HIDDEN = BOXPLUS + '-hidden';
	/** @const */
	var CLASS_UNAVAILABLE = BOXPLUS + '-unavailable';  // indicates that the control is not available in the current context
	/** @const */
	var CLASS_DISABLED = BOXPLUS + '-disabled';        // indicates that the control is disabled
	/** @const */
	var CLASS_START = BOXPLUS + '-start';
	/** @const */
	var CLASS_STOP = BOXPLUS + '-stop';
	/** @const */
	var CLASS_ACTIVE = BOXPLUS + '-active';

	//
	// jQuery extensions
	//

	/**
	* Get the current computed outer width for the first element in the set of matched elements provided that the element is visible.
	* @return Width including padding, border and margin if the element is visible, 0 otherwise.
	*/
	$.fn.trueWidth = function () {
		return this.filter(':visible').size() ? this.outerWidth(true) : 0;
	}

	/**
	* Get the current computed outer height for the first element in the set of matched elements provided that the element is visible.
	* @return Height including padding, border and margin if the element is visible, 0 otherwise.
	*/
	$.fn.trueHeight = function () {
		return this.filter(':visible').size() ? this.outerHeight(true) : 0;
	}

	/**
	* "Safe" dimension of an HTML element.
	* Some browsers give invalid values with obj.width() but others give the meaningless,
	* value "auto" with obj.css('width'); this function bridges the differences.
	*/
	function _safeDimension(obj, dim) {
		var cssvalue = parseInt(obj.css(dim));
		return isNaN(cssvalue) ? obj[dim]() : cssvalue;
	}

	function _safeWidth(obj) {
		return _safeDimension(obj, 'width');
	}

	function _safeHeight(obj) {
		return _safeDimension(obj, 'height');
	}

	/**
	* Margin of an HTML element.
	* @param elem An HTML element as a jQuery object.
	* @param side One of 'top', 'left', 'bottom' or 'right'.
	*/
	function _getMargin(elem, side) {
		return parseInt(elem.css('margin-' + side)) || 0;  // enforce integer value, even if margin is auto or NaN
	}

	/**
	* Anchor query parameters.
	* @param anchor An HTML anchor element as a jQuery object.
	* @return An object of anchor query parameters corresponding to key-value pairs in query string.
	*/
	function _getAnchorParams(anchor) {
		var
			ret = {},
			seg = anchor[0].search.replace(/^\?/,'').split('&');
		for (var i = 0; i < seg.length; i++) {
			if (seg[i]) {
				var s = seg[i].split('=');
				ret[s[0]] = s[1];
			}
		}
		return ret;
	}

	/**
	* Thumbnail image source, inspecting both src and longdesc attribute.
	*/
	function _getThumbnailData(image) {
		var
			src = image.attr('src'),
			longdesc = image.attr('longdesc'),
			thumb = image.attr('data-thumb');
		return {
			src: thumb ? thumb : (
				src && src != 'data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACH5BAAAAAAALAAAAAABAAEAAAICRAEAOw==' ? src : (
					/\.(gif|jpe?g|png)$/i.test(longdesc) ? longdesc : false
				)
			)
		};
	}

	//
	// Initialization
	//

	/**
	* Short-hand selector for DOM elements that belong to the boxplus namespace.
	*/
	function _selector(name, ancestor) {
		return $('.' + BOXPLUS + '-' + name, ancestor);
	}

	/**
	* Appends the pop-up window HTML code to the document and initializes global variables.
	* The HTML code inserted is
		<div id="boxplus">
			<div class="boxplus-background boxplus-hidden"></div>
			<div class="boxplus-dialog boxplus-hidden">
				<div class="boxplus-title"></div>
				<div class="boxplus-main">
					<div class="boxplus-viewer boxplus-hidden">
						<div></div>
						<img />
						<video controls />
						<div class="boxplus-flash"><object><param name="movie" /><embed type="application/x-shockwave-flash" /></object></div>
						<div class="boxplus-prev"></div>
						<div class="boxplus-next"></div>
						<div class="boxplus-resizer">
							<div class="boxplus-enlarge">
							<div class="boxplus-shrink boxplus-disabled">
						</div>
						<div class="boxplus-thumbs">
							<ul></ul>
							<div class="boxplus-rewind"></div>
							<div class="boxplus-forward"></div>
						</div>
						<div class="boxplus-progress"></div>
					</div>
					<div class="boxplus-bottom">
						<div class="boxplus-thumbs">
							<ul></ul>
							<div class="boxplus-rewind"></div>
							<div class="boxplus-forward"></div>
						</div>
						<div class="boxplus-caption">
							<div class="boxplus-title"></div>
							<div class="boxplus-text"></div>
						</div>
						<div class="boxplus-controls">
							<div class="boxplus-prev"></div>
							<div class="boxplus-next"></div>
							<div class="boxplus-start"></div>
							<div class="boxplus-stop boxplus-disabled"></div>
							<div class="boxplus-close"></div>
							<div class="boxplus-download"></div>
							<div class="boxplus-metadata"></div>
						</div>
					</div>
				<div>
				<div class="boxplus-sideways boxplus-disabled">
					<div class="boxplus-thumbs">
						<ul></ul>
						<div class="boxplus-rewind"></div>
						<div class="boxplus-forward"></div>
					</div>
					<div class="boxplus-caption">
						<div class="boxplus-title"></div>
						<div class="boxplus-text"></div>
					</div>
					<div class="boxplus-controls">
						<div class="boxplus-prev"></div>
						<div class="boxplus-next"></div>
						<div class="boxplus-start"></div>
						<div class="boxplus-stop boxplus-disabled"></div>
						<div class="boxplus-close"></div>
						<div class="boxplus-download"></div>
						<div class="boxplus-metadata"></div>
					</div>
				</div>
				<div class="boxplus-lt"></div>
				<div class="boxplus-t"></div>
				<div class="boxplus-rt"></div>
				<div class="boxplus-l"></div>
				<div class="boxplus-m boxplus-hidden"></div>
				<div class="boxplus-r"></div>
				<div class="boxplus-lb"></div>
				<div class="boxplus-b"></div>
				<div class="boxplus-rb"></div>
				<div class="boxplus-progress"></div>
			</div>
		</div>
	*/
	$(function () {  // fired when DOM tree is finished loading
		function _element(name, contents) {
			return '<div' + (name ? ' class="' + BOXPLUS + '-' + ($.isArray(name) ? name.join(' ') : name) + '"' : '') + '>' + (contents ? contents : '') + '</div>';
		}

		// document body
		body = $('body');

		// HTML for navigation controls
		var navhtml = _element('prev') + _element('next');
		var captionhtml = _element('caption', _element('title') + _element('text'));
		var controlshtml = _element('controls', navhtml + _element('start') + _element(['stop', CLASS_DISABLED]) + _element('close') + _element('download') + _element('metadata'));
		var thumbshtml = '<ul />' + _element('rewind') + _element('forward');

		// add elements to HTML DOM tree
		var boxplus = $('<div id="' + BOXPLUS + '">' +
			_element(['background', CLASS_HIDDEN]) +
			_element(['dialog', CLASS_HIDDEN],
				_element('title') +
				_element('main',
					_element(['viewer', CLASS_HIDDEN],
						_element(['content', CLASS_HIDDEN]) +  // must be first element of parent
						'<img />' +
						'<video controls />' +
						_element('flash') +
						navhtml +
						_element('resizer',
							_element('enlarge') +
							_element(['shrink', CLASS_HIDDEN])
						) +
						_element('thumbs', thumbshtml) +
						_element('progress')  // must be last element of parent
					) +
					_element('bottom',
						_element('thumbs', thumbshtml) + captionhtml + controlshtml
					)
				) +
				_element(['sideways', CLASS_DISABLED],
					_element('thumbs', thumbshtml) + controlshtml + captionhtml
				) +
				_element('lt') + _element('t') + _element('rt') +
				_element('l') + _element('m') + _element('r') +
				_element('lb') + _element('b') + _element('rb') +
				_element('progress')  // must be last element of parent
			) +
		'</div>').appendTo(body);

		// background
		background = _selector('background', boxplus).click(hideDialog)

		// dialog
		dialog = _selector('dialog', boxplus);
		caption = _selector('caption', dialog);    // one or multiple captions
		panels = _selector('bottom', dialog).add(_selector('sideways', dialog));

		// image/content viewer
		viewer = _selector('viewer', dialog);
		viewercontent = $('div:first', viewer);
		viewerimage = $('img:first', viewer);
		viewervideo = $('video', viewer);
		viewerflash = _selector('flash', viewer);
		vieweritems = $([viewerimage[0], viewerflash[0]]).add(viewervideo);

		resizer = _selector('resizer', viewer).click(resizeImage);
		shrink = _selector('shrink', resizer);

		// thumbnail bar events
		btnScrollBack = _selector('rewind', dialog).click(_rewindThumbnailSlide).hover(_rewindThumbnailScroll, _stopThumbnailScroll);
		btnScrollForward = _selector('forward', dialog).click(_forwardThumbnailSlide).hover(_forwardThumbnailScroll, _stopThumbnailScroll);
		thumbsBar = _selector('thumbs', dialog);
		thumbs = $('ul', thumbsBar);

		// subscribe to click event for navigation controls
		btnPrev = _selector('prev', dialog).click(previousItem);  // one or multiple controls
		btnNext = _selector('next', dialog).click(nextItem);
		btnStart = _selector('start', dialog).click(startSlideshow);
		btnStop = _selector('stop', dialog).click(stopSlideshow);
		btnClose = _selector('close', dialog).click(hideDialog);
		btnDownload = _selector('download', dialog).click(downloadItem);
		btnMetadata = _selector('metadata', dialog).click(metadataItem);

		// default dialog dimensions to use when there is no image to show
		dialogDefWidth = _safeWidth(dialog);
		dialogDefHeight = _safeHeight(dialog);

		// initial dialog dimensions to use when the pop-up window is opened
		viewer.css({height:0,width:0});  // constrained by minimum viewer width and height
		dialogInitWidth = _safeWidth(dialog);
		dialogInitHeight = _safeHeight(dialog);

		// clone dialog for sizing
		dialogClone = dialog.clone().appendTo(boxplus);
	});

	//
	// Constructors
	//

	/**
	* Binds the lightweight window to appear when image/content links are clicked.
	*/
	$.fn.boxplus = function (settings) {
		return this.boxplusConfigure(settings).click(function (event) {
			showDialog(event.currentTarget);
			return false;  // stop event propagation if registered as event handler
		});
	}

	/**
	* Binds the lightweight window to appear when image links in a gallery are clicked.
	* A gallery should be specified as a list (ul or ol with li as direct children), each of whose elements wraps an individual image.
	*/
	$.fn.boxplusGallery = function (settings) {
		_findGalleryItems(this).boxplus(settings);  // bind to first anchor in each list item
		return this;
	};

	$.fn.boxplusDialog = function (settings) {
		showDialog(this.boxplusConfigure(settings)[0]);  // use DOM node as argument
	}

	/**
	* Configures appearance and behavior for the lightweight pop-up window.
	* @param settings A settings object.
	*/
	$.fn.boxplusConfigure = function (settings) {
		this.data(BOXPLUS, $.extend({}, settings));
		return this;
	}

	/**
	* Configures appearance and behavior for the lightweight pop-up window for all items in a gallery.
	* @param settings A settings object.
	*/
	$.fn.boxplusGalleryConfigure = function (settings) {
		_findGalleryItems(this).boxplusConfigure(settings);
		return this;
	}

	//
	// Hook functions
	//

	/**
	* Extracts the title that belongs to the item currently shown.
	* @param anchor An HTML anchor represented as a jQuery object.
	* @return HTML code to use as image/content caption title.
	*/
	function _getTitle(anchor) {
		var image = $('img:first', anchor);
		return image.size() ? image.attr('alt') : '';
	}

	/**
	* Extracts the description that belongs to the item currently shown.
	* The description will serve as image/content caption text for the item.
	* @param anchor An HTML anchor represented as a jQuery object.
	* @return HTML code to use as caption text.
	*/
	function _getDescription(anchor) {
		return anchor.attr('title');
	}

	/**
	* Extracts the download URL that belongs to the item currently shown.
	* @param anchor An HTML anchor represented as a jQuery object.
	* @return A valid URL, or false.
	*/
	function _getDownloadUrl(anchor) {
		return false;
	}

	/**
	* Extracts the metadata that belongs to the item currently shown.
	* @param anchor An HTML anchor represented as a jQuery object.
	* @return An HTML DOM subtree root as a jQuery object, or an empty string.
	*/
	function _getMetadata(anchor) {
		return '';
	}

	//
	// Public methods
	//

	/**
	* Shows the lightweight pop-up window.
	* @param link The link that has activated the pop-up window.
	*/
	function showDialog(link) {
		var anchor = $(link);
		settings = $.extend({}, defaults, anchor.data(BOXPLUS));  // settings can be cached at global level, only one dialog may be open at once

		// enable associated theme (if any) and disable other themes that might be linked to the page
		var theme = settings.theme;
		if (theme) {
			var disabled = 'disabled';
			$('link[rel=stylesheet][title^=' + BOXPLUS + ']').attr(disabled, disabled).filter('[title="' + BOXPLUS + '-' + theme + '"]').removeAttr(disabled);  // disable unused themes and enable selected theme
		}

		// show shaded background
		background.removeClass(CLASS_HIDDEN);

		// position the pop-up window in the center
		_selector('m', dialog).addClass(CLASS_HIDDEN);
		_selector('title', dialog).addClass(CLASS_UNAVAILABLE);
		dialog.removeClass(CLASS_DISABLED).css({
			width: dialogInitWidth,
			height: dialogInitHeight
		}).css(_center(dialogInitWidth, dialogInitHeight)).removeClass(CLASS_HIDDEN);
		_toggleProgress(dialog, true);

		// register events
		doc.bind('keydown', _onKeyDown);
		if (!settings.contextmenu) {
			doc.bind('contextmenu', _onProhibitedUIAction).bind('dragstart', _onProhibitedUIAction);  // subscribe to right-click (context menu) event and drag start events
		}

		// query URL of images in gallery
		var rel = anchor.attr('rel');
		anchors = rel ? $('a[rel="' + rel + '"]') : anchor;  // related anchors (if any)

		// extract the href attribute from members of the group of related anchors as an array
		var href = anchor.attr('href');
		var hrefs = anchors.map(function () {
			return $(this).attr('href');
		}).get();

		// discard elements that have a previously used href attribute
		anchors = anchors.filter(function (index) {
			return $.inArray($(this).attr('href'), hrefs) >= index;  // this is the first anchor that uses this href
		});		
		
		// add thumbnails
		rtlpos = (rtl = settings.rtl) ? 'right' : 'left';
		thumbs.empty().css({
			left: 'auto',
			right: 'auto'
		}).css(rtlpos, 0);
		anchors.each(function (index) {
			var image = $('img:first', this);
			$('<li />').append((image.size() ? $('<img />').attr(_getThumbnailData(image)) : $()).click(function () {
				stopSlideshow();
				changeItem(index);
			})).appendTo(thumbs);
		});

		// set thumbnail bar dimensions
		thumbsBar.removeClass(CLASS_DISABLED).each(function () {
			// set thumbnail bar availability
			var thumbs = $('ul', this);
			$(this).toggleClass(CLASS_UNAVAILABLE, thumbs.children().size() < 2);
		});

		// toggle thumbnail bars inside/outside image viewport based on settings
		var thumbsoutside = settings.thumbs == 'outside';
		thumbsBar.toggleClass(CLASS_DISABLED, !thumbsoutside).filter(viewer.children()).toggleClass(CLASS_DISABLED, thumbsoutside);

		// toggle slideshow start button
		btnStart.toggleClass(CLASS_UNAVAILABLE, anchors.length < 2 || !settings.slideshow);

		// load first image
		changeItem($.inArray(href, hrefs));  // find the index of the anchor that has been clicked from among those in the link set
	}

	/**
	* Hides the lightweight pop-up window.
	* Fired when the user clicks the close button, clicks outside the pop-up window or presses the ESC key.
	*/
	function hideDialog() {
		stopSlideshow();

		// unregister events
		doc.unbind('keydown', _onKeyDown).unbind('contextmenu', _onProhibitedUIAction).unbind('dragstart', _onProhibitedUIAction);
		dialog.stop(true, true);

		current = -1;  // no image is displayed

		dialog.addClass(CLASS_DISABLED).add(panels).add(viewer).add(background).addClass(CLASS_HIDDEN);
	}

	/**
	* Navigate to the first image/content.
	* Fired when the user clicks the navigate to first control or presses the HOME key.
	*/
	function firstItem() {
		stopSlideshow();
		changeItem(0);
	}

	/**
	* Navigate to the previous image/content.
	* Fired when the user clicks the navigate to previous control or presses the left arrow key.
	*/
	function previousItem() {
		stopSlideshow();
		changeItem(current - 1);
	}

	/**
	* Navigate to the next image/content.
	* Fired when the user clicks the navigate to next control or presses the right arrow key.
	*/
	function nextItem() {
		stopSlideshow();
		changeItem(current + 1);
	}

	/**
	* Navigate to the last image/content.
	* Fired when the user clicks the navigate to last control or presses the END key.
	*/
	function lastItem() {
		stopSlideshow();
		changeItem(anchors.length-1);
	}

	/**
	* Navigate to the image/content with the specified index.
	* Fired when the user clicks a thumbnail in the scrollable thumbnail bar.
	*/
	function changeItem(index) {
		var count = anchors.length;
		if (index != current && (settings.loop || index >= 0 && index < count)) {
			current = (index + count) % count;  // avoid mod operator with negative numbers
			_setShrunk(true);
			_changeItem();
		}
	}

	/**
	* Stop the slideshow timer unconditionally.
	* Fired when the user clicks the stop control.
	*/
	function stopSlideshow() {
		_clearSlideshowTimer();
		btnStop.addClass(CLASS_DISABLED);
		btnStart.removeClass(CLASS_DISABLED);
	}

	/**
	* Start the slideshow timer.
	* Fired when the user clicks the play control.
	*/
	function startSlideshow() {
		_startSlideshowTimer();
		btnStart.addClass(CLASS_DISABLED);
		btnStop.removeClass(CLASS_DISABLED);
	}

	/**
	* Enlarges or shrinks an image, as appropriate.
	* Fired when the user clicks the enlarge/shrink control in the upper right corner of the window.
	*/
	function resizeImage() {
		stopSlideshow();
		_setShrunk(!_isShrunk());
		_changeItem();
	}

	/**
	* Prepares an item for display in the viewer possibly using a preloaded image.
	*/
	function refreshItem() {
		// hide image viewer and show progress indicator
		viewer.addClass(CLASS_HIDDEN);
		_toggleProgress(viewer, false);
		_toggleProgress(dialog, true);

		// hide caption and disable navigation controls
		panels.addClass(CLASS_HIDDEN);

		// get target dimensions and placement for dialog
		var
			autofit = settings.autofit,
			dimensions = {},
			dlgdimensions = {},
			position = {};
		_getPlacement(autofit && _isShrunk(), dimensions, dlgdimensions, position);  // resizing is enabled and image can expand

		// set image viewer width, height and image source
		viewer.css(dimensions);
		viewerimage.attr('src', anchors.eq(current).attr('href'));

		// turn on resizer if image has been reduced to fit window
		resizer.toggleClass(CLASS_UNAVAILABLE, !autofit || !preloader || dimensions.width == preloader.width && _isShrunk());

		thumbs.each(function () {
			$(this).children().removeClass(CLASS_ACTIVE).eq(current).addClass(CLASS_ACTIVE);
		});

		// resize dialog box with animation (image caption not shown yet)
		_selector('m', dialog).addClass(CLASS_HIDDEN);
		dialog.animate($.extend(position, dlgdimensions), settings.duration, settings.easing, _showItem);
	}

	function downloadItem() {
		stopSlideshow();
		window.location.href = settings.download(anchors.eq(current));
	}

	function metadataItem() {
		stopSlideshow();
		viewer.children().slice(0,-1).toggleClass(CLASS_HIDDEN);  // do not toggle progress bar, which is the last element
	}

	$.boxplus = {
		/** Displays the specified item in the gallery. */
		change: changeItem,
		/** Displays the previous item in the gallery. */
		previous: previousItem,
		/** Displays the next item in the gallery. */
		next: nextItem,
		refresh: refreshItem,
		/** Changes configuration defaults. */
		configure: function (settings) {
			return $.extend(defaults, settings);  // updates left-hand side object
		},

		/**
		* Fired when the item to be shown changes.
		* function (href : string, index : int) : void
		*/
		onchange: $.noop
	};

	//
	// Private methods for image display
	//

	/**
	* Finds anchors that belong to a gallery.
	* @param gallery The root node of a gallery DOM subtree wrapped in a jQuery object.
	* @return A jQuery collection of anchors in a gallery.
	*/
	function _findGalleryItems(gallery) {
		// fetch or construct gallery identifier
		var id = gallery.attr('id');
		id = id ? BOXPLUS + '-' + id : BOXPLUS;

		$('li', gallery).each(function () {
			$('a:first', this).attr('rel', id);
		});
		return $('a[rel=' + id + ']', gallery);
	}

	/**
	* Initiates changing the image/content displayed in the lightweight pop-up window.
	*/
	function _changeItem() {
		_clearSlideshowTimer();
		dialog.stop(true, true);
		thumbs.stop();

		// hide caption and disable navigation controls
		panels.addClass(CLASS_HIDDEN);

		// show progress indicator
		_toggleProgress(viewer, true);

		// clear metadata
		viewercontent.empty();

		// hide image, video and flash viewer
		vieweritems.addClass(CLASS_UNAVAILABLE);

		var anchor = anchors.eq(current);
		var a = anchor[0];
		var
			href = anchor.attr('href'),
			path = a.pathname;

		// fire onchange event
		$.boxplus.onchange(href, current);

		// fetch new content to be shown
		if (/^#/.test(href)) {  // content in the same document
			viewercontent.append($(href).clone().contents());  // clone DOM subtree
			_prepareText();
		} else if (/\.(txt|html?)$/i.test(path)) {
			_loadContent(href);
		} else if (/\.(gif|jpe?g|png)$/i.test(path)) {  // preload image
			_loadImage(anchor);
		} else if (/\.(mov|mpe?g|ogg|swf|webM|wmv)$/i.test(path) || /youtube\.com$/.test(a.hostname)) {
			_loadVideo(anchor);
		} else {  // content from external source using URL
			$.ajax({
				url: href,
				success: function (response, status, xhdr) {
					var contentType = xhdr.getResponseHeader("Content-Type");  // content type is empty when browsing locally, must use extension instead
					if (/^text\/(plain|html)/.test(contentType)) {
						_loadContent(href);
					} else if (/^image\/(gif|jpeg|png)/.test(contentType)) {
						_loadImage(anchor);
					} else if (/^application\/x-shockwave-flash/.test(contentType)) {
						_loadVideo(anchor);
					}
				},
				type: 'head'
			});
		}
	}

	/**
	* Prepares HTML content for display in the viewer.
	* Content-type is assumed "text/plain" or "text/html".
	* @param href The URL to the content to display.
	*/
	function _loadContent(href) {
		viewercontent.load(href, {}, _prepareText);
	}

	/**
	* Prepares an image to be shown in the viewer.
	* Content-type is assumed one of "image/gif", "image/jpeg" or "image/png".
	* @param anchor An HTML anchor as a jQuery object.
	*/
	function _loadImage(anchor) {
		// set metadata
		var meta = settings.metadata(anchor);
		if (meta) {
			viewercontent.append($.inArray($.type(meta), ['boolean','number','string']) >= 0 ? meta : meta.clone());
		}

		// display image when image has been loaded, src must be initialized last for some browsers
		viewerimage.removeClass(CLASS_UNAVAILABLE);
		$(preloader = new Image()).load(refreshItem).error(_prepareText).attr('src', anchor.attr('href'));
	}

	/**
	* Prepares a video to be shown in the viewer.
	* @param anchor An HTML anchor as a jQuery object.
	*/
	function _loadVideo(anchor) {
		var
			href = anchor.attr('href'),
			params = _getAnchorParams(anchor);
		var
			w = parseInt(params.width) || 640,
			h = parseInt(params.height) || 480;
		var dims = {
			width: w,
			height: h
		};
		var pathname = anchor[0].pathname;
		if (/\.(ogg|webM)$/i.test(pathname)) {
			viewervideo.attr($.extend({
				src: href
			}, dims)).removeClass(CLASS_UNAVAILABLE);
		} else {
			var type = 'application/x-shockwave-flash';
			var classid = 'D27CDB6E-AE6D-11cf-96B8-444553540000';

			if (/\.mov$/i.test(pathname)) {
				type = 'video/quicktime';
				classid = '02BF25D5-8C17-4B23-BC80-D3488ABDDC6B';
			}
			viewerflash.empty().append(_getObjectHTML(href, type, dims, classid)).removeClass(CLASS_UNAVAILABLE);
		}
		preloader = $.extend({}, dims);
		refreshItem();
	}

	/**
	* Builds a custom HTML object with the specified dimensions and attributes.
	* Uses nested <object /> HTML elements.
	*/
	function _getObjectHTML(url, type, dims, classid) {
		return '<object' + _getAsAttributeList($.extend({
				classid: 'clsid:' + classid
			}, dims)) + '>' +
			_getAsParameterList({
				movie: url
			}) +
			'<!--[if lt IE 9]><!--><object' + _getAsAttributeList($.extend({
				type: type,
				data: url
			}, dims)) + '></object><!--<![endif]-->' +
		'</object>';
	}

	/**
	* Converts an object into a name="value" HTML attribute list.
	*/
	function _getAsAttributeList(attrs) {
		var s = '';
		for (var name in attrs) {
			s += ' ' + name + '="' + attrs[name] + '"';
		}
		return s;
	}

	/**
	* Converts an object into a list of HTML <param /> elements.
	*/
	function _getAsParameterList(attrs) {
		var s = '';
		for (var name in attrs) {
			s += '<param name="' + name + '" value="' + attrs[name] + '" />';
		}
		return s;
	}

	/**
	* Prepares HTML content for display in the viewer.
	*/
	function _prepareText() {
		preloader = null;
		refreshItem();
	}

	/**
	* Displays the image in the viewer.
	*/
	function _showItem() {
		_selector('m', dialog).removeClass(CLASS_HIDDEN);
		var pos = _getRTLPosition(thumbs.children().eq(current));  // left offset of active thumbnail on thumbs ribbon w.r.t. left edge of viewer
		if (thumbindex < 0) {
			var
				vw = _safeWidth(thumbsBar),  // width of viewport
				tw = _safeWidth(thumbs);     // total width of thumbnail ribbon
				                             // tw - vw = maximum value permitted as left offset w.r.t. left edge of viewer
			thumbs.css(rtlpos, -(tw < vw ? _getRTLPosition(thumbs.children().eq(0)) : Math.min(pos, tw - vw)));
		} else {
			thumbindex = current;
			thumbs.css(rtlpos, -pos);
		}
		_updateThumbnailNavigation();

		// show image viewer
		viewer.removeClass(CLASS_HIDDEN);

		// show navigation controls as appropriate
		var loop = settings.loop;
		btnPrev.toggleClass(CLASS_UNAVAILABLE, !loop && current == 0);
		btnNext.toggleClass(CLASS_UNAVAILABLE, !loop && current >= anchors.length-1);

		// reset metadata view state
		viewer.children().removeClass(CLASS_HIDDEN);

		// show action controls as appropriate
		var hasimage = preloader && preloader.src;
		var hascontent = !viewercontent.is(':empty');
		btnDownload.toggleClass(CLASS_UNAVAILABLE, !settings.download(anchors.eq(current)));
		btnMetadata.toggleClass(CLASS_UNAVAILABLE, !hasimage || !hascontent);
		viewercontent.addClass(CLASS_HIDDEN);
		hasimage || !hascontent || metadataItem();  // show metadata if there is no image

		// remove wait indicators
		_toggleProgress(dialog, false);

		// add (or hide) caption text
		_setCaption(dialog, false);

		// resize dialog to show caption text
		var target = {
			width: _safeWidth(dialog) + _selector('sideways', dialog).trueWidth(),
			height: _safeHeight(dialog) + _heightExtension(dialog)
		};
		dialog.animate(target, settings.duration, settings.easing, function () {
			panels.removeClass(CLASS_HIDDEN);  // displays the image caption text
			if (!settings.loop && current >= anchors.length-1) {  // automatically stop slideshow at last image
				stopSlideshow();
			}
			if (_isSlideshowActive()) {
				_startSlideshowTimer();
			}
		});
	}

	//
	// Private methods for slideshow
	//

	function _isSlideshowActive() {
		return !btnStop.hasClass(CLASS_DISABLED);
	}

	/**
	* Sets a slideshow timer.
	*/
	function _startSlideshowTimer() {
		timer = setTimeout(function () {
			changeItem(current + 1);
		}, settings.slideshow);
	}

	/**
	* Clears a slideshow timer.
	*/
	function _clearSlideshowTimer() {
		if (timer) {
			clearTimeout(timer);
			timer = 0;
		}
	}

	//
	// Private methods for thumbnail bar display
	//

	function _getRTLPosition(elem) {
		var left = elem.position().left;
		return rtl ? elem.offsetParent().width() - elem.width() - left : left;
	}

	/**
	* Updates the visibility of thumbnail navigation controls.
	*/
	function _updateThumbnailNavigation() {
		var
			diff = _safeWidth(thumbs.parent()) - _safeWidth(thumbs),
			pos = _getRTLPosition(thumbs);
		btnScrollBack.toggleClass(CLASS_HIDDEN, pos >= 0);
		btnScrollForward.toggleClass(CLASS_HIDDEN, diff > 0 || pos <= diff);
	}

	/**
	* Slides the thumbnail navigation bar by a single thumbnail image.
	*/
	function _thumbnailSlide() {
		stopSlideshow();

		var target = {};
		target[rtlpos] = -_getRTLPosition(thumbs.children().eq(thumbindex));
		thumbs.animate(target, 'fast', 'linear', _updateThumbnailNavigation);

		return false;
	}

	/**
	* Slides the thumbnail ribbon backwards by a single thumbnail image.
	* Triggered by a mouse click.
	*/
	function _rewindThumbnailSlide() {
		if (thumbindex > 0) {
			thumbindex--;
			_thumbnailSlide();
		}
	}

	/**
	* Slides the thumbnail ribbon forwards by a single thumbnail image.
	* Triggered by a mouse click.
	*/
	function _forwardThumbnailSlide() {
		if (thumbindex >= 0 && thumbindex+1 < anchors.size()) {
			thumbindex++;
			_thumbnailSlide();
		}
	}

	/**
	* Scrolls the thumbnail ribbon towards the first thumbnail image.
	* Triggered by the mouse moving over the navigation control.
	*/
	function _rewindThumbnailScroll() {
		if (thumbindex < 0) {
			stopSlideshow();

			var target = {};
			target[rtlpos] = 0;
			thumbs.animate(target, -4 * _getRTLPosition(thumbs), 'linear', _updateThumbnailNavigation);  // "left" (or "right" for RTL) is always a negative number
		}
	}

	/**
	* Scrolls the thumbnail ribbon towards the last thumbnail image.
	* Triggered by the mouse moving over the navigation control.
	*/
	function _forwardThumbnailScroll() {
		if (thumbindex < 0) {
			stopSlideshow();

			var
				vw = _safeWidth(thumbsBar),
				tw = _safeWidth(thumbs);
			var pos = _getRTLPosition(thumbs);  // current left offset of thumbs ribbon w.r.t. left edge of viewer
			var minpos = vw - tw;               // maximum negative value permitted as left offset w.r.t. left edge of viewer

			if (tw + pos < vw) {  // right end of ribbon is to the right of right edge of viewer
				_updateThumbnailNavigation();
			} else {
				var target = {};
				target[rtlpos] = minpos;
				thumbs.animate(target, -4 * (minpos - pos), 'linear', _updateThumbnailNavigation);
			}
		}
	}

	/**
	* Fired when the mouse is no longer over one of the thumbnail navigation controls.
	*/
	function _stopThumbnailScroll() {
		thumbs.stop();
		_updateThumbnailNavigation();
	}

	//
	// Private methods for resizer control
	//

	/**
	* Gets whether the image currently displayed is in shrunk state.
	*/
	function _isShrunk() {
		return shrink.hasClass(CLASS_HIDDEN);
	}

	/**
	* Sets whether the image currently displayed is in shrunk state.
	* @param toggle If true, hide enlarge button and show shrink button; if false, vice versa.
	*/
	function _setShrunk(toggle) {
		_selector('enlarge', resizer).toggleClass(CLASS_HIDDEN, !toggle);
		shrink.toggleClass(CLASS_HIDDEN, toggle);
	}

	//
	// Private methods for labels
	//

	/**
	* Sets caption title and text.
	* @param caption A jQuery object to assign the caption to.
	*/
	function _setCaption(caption, sizing) {
		var anchor = anchors.eq(current);
		var
			title = settings.title(anchor),
			text = settings.description(anchor, sizing);
		_selector('title', caption).toggleClass(CLASS_UNAVAILABLE, !title).html(title);
		_selector('text', caption).toggleClass(CLASS_UNAVAILABLE, !text || text == title).empty().append(text);
	}

	//
	// Private methods for progress indicator
	//

	/**
	* Enables or disables a progress indicator.
	* A progress indicator is a PNG image with alpha transparency
	*/
	function _toggleProgress(ctrl, on) {
		var indicator = _selector('progress', ctrl).toggleClass(CLASS_HIDDEN, !on);
		window.clearInterval(indicator.data(BOXPLUS));
		if (on) {
			indicator.data(BOXPLUS, window.setInterval(function () {
				indicator.css('background-position', progress = (progress - 32) % 384);  // 384px = 12 states * 32px width
			}, 150));
		}
	}

	//
	// Private methods for dialog positioning
	//

	/**
	* The height the dialog grows when caption and controls are shown.
	*/
	function _heightExtension(dlg) {
		return _selector('caption', dlg).trueHeight() + _selector('controls', dlg).trueHeight();
	}

	/**
	* Returns coordinates to place a rectangle in the middle of the browser window with absolute positioning.
	*/
	function _center(width, height) {
		var
			x = $(window).innerWidth() / 2,
			y = $(window).innerHeight() / 2;
		var max = Math.max;
		return {
			left: max(0, $(window).scrollLeft() + x - width / 2),  // user should always be able to view the full image by scrolling the document
			top: max(0, $(window).scrollTop() + y - height / 2)
		};
	}

	/**
	* Get target dimensions and placement used for centering the lightweight pop-up window.
	* @param resize Whether to resize the pop-up window to fit to screen.
	*/
	function _getPlacement(resize, dimensions, dlgdimensions, position) {
		// get image dimensions
		$.extend(dimensions, {
			width: preloader ? preloader.width : dialogDefWidth,
			height: preloader ? preloader.height : dialogDefHeight
		});

		// add caption text, which affects centering (and whether dialog fits into browser window)
		_setCaption(_selector('caption', dialogClone.removeClass(CLASS_UNAVAILABLE)), true);

		// copy thumbs from originals
		var thumbsClone = _selector('thumbs > ul', dialogClone);
		thumbs.eq(0).children().clone().appendTo(thumbsClone);

		// set thumbnail navigation bar visibility based on settings in original dialog
		_selector('thumbs', dialogClone).each(function (index) {
			var bar = thumbsBar.eq(index)
			$(this).toggleClass(CLASS_DISABLED, bar.hasClass(CLASS_DISABLED)).toggleClass(CLASS_UNAVAILABLE, bar.hasClass(CLASS_UNAVAILABLE));
		});

		// set width and height extension of dialog in second animation phase
		var
			sidewaysClone = _selector('sideways', dialogClone),
			mainClone = _selector('main', dialogClone);
		var w = mainClone.trueWidth() - _safeWidth(mainClone) + sidewaysClone.trueWidth();

		// set image/content viewer width and height in dialog clone
		var viewerClone = _selector('viewer', dialogClone.css('width', dimensions.width + w)).css(dimensions);

		if (resize) {
			var win_w = $(window).innerWidth() - _getMargin(body, 'left') - _getMargin(body, 'right');

			// compute image/content viewer width using dialog clone
			var dlg_w = dialogClone.outerWidth(true);
			while (dlg_w > win_w) {
				var ratio = win_w / dlg_w;
				dimensions.width *= ratio;
				dimensions.height *= ratio;
				viewerClone.css(dimensions);
				dlg_w = dialogClone.css('width', dimensions.width + w).outerWidth(true);
			}
		}

		var dlg_h = dialogClone.outerHeight(true);
		if (resize) {
			var win_h = $(window).innerHeight() - _getMargin(body, 'top') - _getMargin(body, 'bottom');

			// compute image/content viewer height using dialog clone
			while (dlg_h > win_h) {
				ratio = win_h / dlg_h;
				dimensions.width *= ratio;
				dimensions.height *= ratio;
				viewerClone.css(dimensions);
				dlg_h = dialogClone.css('width', dimensions.width + w).outerHeight(true);  // may still exceed window height if resize caused caption text to re-flow
			}
		}
		dlgdimensions.width = _safeWidth(dialogClone) - sidewaysClone.trueWidth();
		dlgdimensions.height = _safeHeight(dialogClone) - _heightExtension(dialogClone);
		$.extend(position, _center(dialogClone.trueWidth(), dlg_h));  // use viewer height extended with caption text height when calculating vertical middle
		thumbsClone.empty();
		dialogClone.addClass(CLASS_UNAVAILABLE);
	}

	//
	// Events
	//

	/**
	* Fired when the user presses a key while the lightweight pop-up window is shown.
	* This event is associated with the document element.
	*/
	function _onKeyDown(event) {
		if ($.inArray(event.target.tagName.toLowerCase(), ['input','textarea']) < 0) {  // let form elements handle their own input
			var keyindex = $.inArray(event.which, [27,37,39,36,35]);  // keys are [ESC, left arrow, right arrow, home, end]
			keyindex < 0 || [hideDialog,previousItem,nextItem,firstItem,lastItem][keyindex]();
			return false;  // cancel event propagation
		}
	}

	/**
	* Fired when the user right-clicks on an element
	* This event is associated with the document element.
	*/
	function _onProhibitedUIAction(event) {
		return !$('img', thumbs).add(viewerimage).filter(event.target).size();  // prevent right-click on image
	}
})(__jQuery__);