(function($){

var dropShadowZindex = 1;  //z-index counter

$.fn.dropShadow = function(options)
{
	// Default options
	var opt = $.extend({
		left: 2,
		top: 2,
		blur: 2,
		opacity: .5,
		color: "black",
		swap: false
		}, options);
	var jShadows = $([]);  //empty jQuery collection
	
	// Loop through original elements
	this.not(".dropShadow").each(function()
	{
		var jthis = $(this);
		var shadows = [];
		var blur = (opt.blur <= 0) ? 0 : opt.blur;
		var opacity = (blur == 0) ? opt.opacity : opt.opacity / (blur * 8);
		var zOriginal = (opt.swap) ? dropShadowZindex : dropShadowZindex + 1;
		var zShadow = (opt.swap) ? dropShadowZindex + 1 : dropShadowZindex;
		
		// Create ID for shadow
		var shadowId;
		if (this.id) {
			shadowId = this.id + "_dropShadow";
		}
		else {
			shadowId = "ds" + (1 + Math.floor(9999 * Math.random()));
		}

		// Modify original element
		$.data(this, "shadowId", shadowId); //store id in expando
		$.data(this, "shadowOptions", options); //store options in expando
		jthis
			.attr("shadowId", shadowId)
			.css("zIndex", zOriginal);
		if (jthis.css("position") != "absolute") {
			jthis.css({
				position: "relative",
				zoom: 1 //for IE layout
			});
		}

		// Create first shadow layer
		bgColor = jthis.css("backgroundColor");
		if (bgColor == "rgba(0, 0, 0, 0)") bgColor = "transparent";  //Safari
		if (bgColor != "transparent" || jthis.css("backgroundImage") != "none" 
				|| this.nodeName == "SELECT" 
				|| this.nodeName == "INPUT"
				|| this.nodeName == "TEXTAREA") {		
			shadows[0] = $("<div></div>")
				.css("background", opt.color);								
		}
		else {
			shadows[0] = jthis
				.clone()
				.removeAttr("id")
				.removeAttr("name")
				.removeAttr("shadowId")
				.css("color", opt.color);
		}
		shadows[0]
			.addClass("dropShadow")
			.css({
				height: jthis.outerHeight(),
				left: blur,
				opacity: opacity,
				position: "absolute",
				top: blur,
				width: jthis.outerWidth(),
				zIndex: zShadow
			});
			
		// Create other shadow layers
		var layers = (8 * blur) + 1;
		for (i = 1; i < layers; i++) {
			shadows[i] = shadows[0].clone();
		}

		// Position layers
		var i = 1;			
		var j = blur;
		while (j > 0) {
			shadows[i].css({left: j * 2, top: 0});           //top
			shadows[i + 1].css({left: j * 4, top: j * 2});   //right
			shadows[i + 2].css({left: j * 2, top: j * 4});   //bottom
			shadows[i + 3].css({left: 0, top: j * 2});       //left
			shadows[i + 4].css({left: j * 3, top: j});       //top-right
			shadows[i + 5].css({left: j * 3, top: j * 3});   //bottom-right
			shadows[i + 6].css({left: j, top: j * 3});       //bottom-left
			shadows[i + 7].css({left: j, top: j});           //top-left
			i += 8;
			j--;
		}

		// Create container
		var divShadow = $("<div></div>")
			.attr("id", shadowId) 
			.addClass("dropShadow")
			.css({
				left: jthis.position().left + opt.left - blur,
				marginTop: jthis.css("marginTop"),
				marginRight: jthis.css("marginRight"),
				marginBottom: jthis.css("marginBottom"),
				marginLeft: jthis.css("marginLeft"),
				position: "absolute",
				top: jthis.position().top + opt.top - blur,
				zIndex: zShadow
			});

		// Add layers to container	
		for (i = 0; i < layers; i++) {
			divShadow.append(shadows[i]);
		}
		
		// Add container to DOM
		jthis.after(divShadow);

		// Add shadow to return set
		jShadows = jShadows.add(divShadow);

		// Re-align shadow on window resize
		$(window).resize(function()
		{
			try {
				divShadow.css({
					left: jthis.position().left + opt.left - blur,
					top: jthis.position().top + opt.top - blur
				});
			}
			catch(e){}
		});
		
		// Increment z-index counter
		dropShadowZindex += 2;

	});  //end each
	
	return this.pushStack(jShadows);
};


$.fn.redrawShadow = function()
{
	// Remove existing shadows
	this.removeShadow();
	
	// Draw new shadows
	return this.each(function()
	{
		var shadowOptions = $.data(this, "shadowOptions");
		$(this).dropShadow(shadowOptions);
	});
};


$.fn.removeShadow = function()
{
	return this.each(function()
	{
		var shadowId = $(this).shadowId();
		$("div#" + shadowId).remove();
	});
};


$.fn.shadowId = function()
{
	return $.data(this[0], "shadowId");
};


$(function()  
{
	// Suppress printing of shadows
	var noPrint = "<style type='text/css' media='print'>";
	noPrint += ".dropShadow{visibility:hidden;}</style>";
	$("head").append(noPrint);
});

})(jQuery);