/*
 * jQuery Backstretch 1.0
 * http://srobbin.com/jquery-plugins/jquery-backstretch/
 *
 * Add a dynamically-resized background image to the page
 *
 * Copyright (c) 2009 Scott Robbin (srobbin.com)
 * Dual licensed under the MIT and GPL licenses.
*/

(function($) {

	$.backstretch = function(src, options, callback) {
		var settings = {
			hideUntilReady: true, // Hide the image until it's finished loading
			speed: 0 // fadeIn speed for background after image loads (e.g. "fast" or 500)
		},
		imgRatio;
    
		// 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) {    
			                src = src + "?" + (new Date()).getTime();

				var commonCSS = {
					left: 0,
					top: 0
				},
				wrap = $("<div />").attr("id", "backstretch-wrap")
				.css( $.extend(commonCSS, {
					position: "absolute",
					zIndex: -1
				}) ),
				container = $("<div />").attr("id", "backstretch")
				.css( $.extend(commonCSS, {
					position: "fixed",
					overflow: "hidden",
					zIndex: -1
				}) )
				.appendTo(wrap),
				img = $("<img />").attr("src", src)
				.bind("load", function() {
					var self = $(this);
					imgRatio = self.width() / self.height();
					_adjustBG(function() {
						if( settings.hideUntilReady )
							self.fadeIn(settings.speed, function(){
								// Callback, if necessary
								if(typeof callback == "function") callback();
							});
					});
				});
        
				if(settings.hideUntilReady) img.hide();
				img.appendTo(container);
          
				$("body").prepend(wrap);

				// Adjust the background size when the window is resized
				$(window).resize(_adjustBG);
			}
      
		}
    
		function _adjustBG(callback) {
			var bgWidth = $(window).width(),
			bgHeight = bgWidth / imgRatio;

			if(bgHeight < $(window).height()) {
				bgHeight = $(window).height();
				bgWidth = bgHeight * imgRatio;
			}

			$("#backstretch img").width( bgWidth ).height( bgHeight );
      
			if (typeof callback == "function") callback();
		}
	};
  
})(jQuery);