/*
 * jQuery Backstretch
 * Version 1.2.0
 * http://srobbin.com/jquery-plugins/jquery-backstretch/
 *
 * Add a dynamically-resized background image to the page
 *
 * Copyright (c) 2011 Scott Robbin (srobbin.com)
 * Dual licensed under the MIT and GPL licenses.
 */

(function($) {

	$.backstretch = function(src, options, callback) {
		var defaultSettings = {
			centeredX: true,         // Should we center the image on the X axis?
			centeredY: true,         // Should we center the image on the Y axis?
			speed: 0,                // fadeIn speed for background after image loads (e.g. "fast" or 500)
			opacity: undefined       // opacity to reach after image loads (0 to 1)
		},
				container = $("#backstretch"),
				settings = container.data("settings") || defaultSettings, // If this has been called once before, use the old settings as the default
				existingSettings = container.data('settings'),
				rootElement = ("onorientationchange" in window) ? $(document) : $(window), // hack to acccount for iOS position:fixed shortcomings
				imgRatio, bgImg, bgWidth, bgHeight, bgOffset, bgCSS;

		// Extend the settings with those the user has provided
		if ( options && typeof options == "object" ) $.extend(settings, options);

		// Initialize
		$(document).ready(_init);

		// For chaining
		return this;

		function _init() {
			// Prepend image, wrapped in a DIV, with some positioning and zIndex voodoo
			if ( src ) {
				var img;

				// If this is the first time that backstretch is being called
				if ( container.length == 0 ) {
					container = $("<div />").attr("id", "backstretch")
							.css({left: 0, top: 0, position: "fixed", overflow: "hidden", zIndex: -999999, margin: 0, padding: 0});
				} else {
					// Prepare to delete any old images
					container.find("img").addClass("deleteable");
				}

				img = $("<img />").css({position: "fixed", display: "none", margin: 0, padding: 0, border: "none"})
						.bind("load", function() {
							var self = $(this);

							self.css({width: "auto", height: "auto"});
							imgRatio = this.width / this.height;

							_adjustBG(function() {
								var fade_callback = function() {
									// Remove the old images, if necessary.
									container.find('.deleteable').remove();
									// Callback
									if ( typeof callback == "function" ) callback();
								};
								if (typeof(settings.opacity) != 'undefined') {
									self.css({
										display: 'block',
										opacity: 0
									});
									self.animate(
										{
											opacity: settings.opacity
										},
										settings.speed,
										fade_callback
									);
								}
								else {
									self.fadeIn(settings.speed, fade_callback);
								}
							});

						})
						.appendTo(container);

				// Append the container to the body, if it's not already there
				if ( $("body #backstretch").length == 0 ) {
					$("body").prepend(container);
				}

				// Attach the settings
				container.data("settings", settings);

				img.attr("src", src); // Hack for IE img onload event
				// Adjust the background size when the window is resized or orientation has changed (iOS)
				$(window).resize(_adjustBG);
			}
		}

		function _adjustBG(fn) {
			try {
				bgCSS = {left: 0, top: 0}
				bgWidth = rootElement.width();
				bgHeight = bgWidth / imgRatio;

				// Make adjustments based on image ratio
				// Note: Offset code provided by Peter Baker (http://ptrbkr.com/). Thanks, Peter!
				if ( bgHeight >= rootElement.height() ) {
					bgOffset = (bgHeight - rootElement.height()) / 2;
					if ( settings.centeredY ) $.extend(bgCSS, {top: "-" + bgOffset + "px"});
				} else {
					bgHeight = rootElement.height();
					bgWidth = bgHeight * imgRatio;
					bgOffset = (bgWidth - rootElement.width()) / 2;
					if ( settings.centeredX ) $.extend(bgCSS, {left: "-" + bgOffset + "px"});
				}

				$("#backstretch img:last").width(bgWidth).height(bgHeight).css(bgCSS);
			} catch( err ) {
				// IE7 seems to trigger _adjustBG before the image is loaded.
				// This try/catch block is a hack to let it fail gracefully.
			}

			// Executed the passed in function, if necessary
			if ( typeof fn == "function" ) fn();
		}
	};

})(jQuery);