/**
 * jQuery Grid Overlay plugin
 *
 * http://code.google.com/p/jsgridoverlay/
 *
 * Copyright (c) 2006 - 2008 Michael Allanson, Pete Goodman, Richard Hallows
 *
 * $Id: jquery.gridoverlay.js 11 2008-09-17 17:56:41Z richhallows $
 *
 * Dual licensed under the MIT and GPL licenses:
 *   http://www.opensource.org/licenses/mit-license.php
 *   http://www.gnu.org/licenses/gpl.html
 *
 * Requires:
 *   http://www.stilbuero.de/2006/09/17/cookie-plugin-for-jquery/
 */
(function($) {

	$.gridOverlay = function(url, settings) {
		// define defaults and override with settings, if available
		settings = $.extend({
			imgExt: "png",
			gridId: "jgrid-overlay",
			gridPos: "50% top",
			gridRepeat: "no-repeat",
			opacityDefault: 1,
			opacityIncrement: 0.1
		}, settings);

		// set keycodes
		var toggleKeys = [59, 186, 90]; // ;
		var downOpacityKeys = [219, 91, 123]; // [
		var upOpacityKeys = [221, 93, 125]; // ]

		// get or calculate vars
		var docHeight = $(document).height();
		var bodyId = $("body").attr("id");
		var imgSrc = url+bodyId+"."+settings.imgExt;

alert(imgSrc);

		// create dom grid element
		var $grid = $('<div></div>');
		$grid.attr('id', settings.gridId);
		$grid.css({
			width: "100%",
			position: "absolute",
			top: "0pt",
			left: "0pt",
			zIndex: 1000,
			height: docHeight+"px",
			backgroundImage: "url("+imgSrc+")",
			backgroundPosition: settings.gridPos,
			backgroundRepeat: settings.gridRepeat,
			opacity: settings.opacityDefault
		});

		// maintain state
		if ($.cookie('gridOverlayState') == 'on') {
			$("body").prepend($grid);
			$grid.css("opacity", $.cookie('gridOverlayOpacity'));
		}

		// keyboard events
		$("html").keydown(function (e) {

			if (e.ctrlKey)	{

				if (jQuery.inArray(e.which, toggleKeys)!= -1) {
					toggleOverlay();
				}

				if (jQuery.inArray(e.which, upOpacityKeys)!= -1) {  //increase opacity
					var currOpacity = parseFloat($grid.css("opacity"));
					var newOpacity = currOpacity + settings.opacityIncrement;

					if ($.cookie('gridOverlayState') == 'off') {  // switch on overlay
						toggleOverlay();
					}

					if (newOpacity <= 1) { // turn opacity up
						$.cookie('gridOverlayOpacity', newOpacity);
						$grid.css("opacity", newOpacity);
					}
				}

				if (jQuery.inArray(e.which, downOpacityKeys)!= -1) {  //decrease opacity
					var currOpacity = parseFloat($grid.css("opacity"));
					var newOpacity = currOpacity - settings.opacityIncrement;

					if ((currOpacity <= 0) && ($.cookie('gridOverlayState') == 'on')) {  // switch off overlay
						toggleOverlay();

					} else if ($.cookie('gridOverlayState') == 'on') { // turn opacity down
						$.cookie('gridOverlayOpacity', newOpacity);
						$grid.css("opacity", newOpacity);
					}
				}
			}
		});

		/**
		 * Toggle the overlay
		 *
		 * @returns void
		 */
		function toggleOverlay() {

			// if exists then remove, else add to dom
			if ($("#"+settings.gridId).length) {
				$.cookie('gridOverlayState', 'off');
				$grid.remove();
			} else {
				$.cookie('gridOverlayState', 'on');
				$("body").prepend($grid);

				if (typeof $.cookie('gridOverlayState') == "string") {
					$grid.css("opacity", $.cookie('gridOverlayOpacity'));
				}
				
				// display errors if there are any
				errorCheck();
			}
		};

		/**
		 * Display an error within the grid holder
		 *
		 * @param string message The message to display
		 * @param string errorType The type of error message
		 * @returns void
		 */
		function showError(message, errorType) {
			
			// set id for error div
			var errorId = settings.gridId + '-' + errorType + 'error';

			// clear existing errors
			$grid.children('#' + errorId).each(function() { 
				$(this).remove();
			}); 

			// create dom grid element as jquery object
			var $error = $('<div></div>');
			$error.attr('id', errorId);
			$error.css({
				border: "1px solid red",
				backgroundColor: "red",
				fontWeight: "bold",
				textAlign: "center"
			});
			$error.text(message);
			$grid.prepend($error);
		};
		
		/**
		 * Checks for any errors
		 *
		 * @returns void
		 */
		function errorCheck() {
			if (bodyId == '') {
				showError('Error: No id on body', 'noId');
			} else {
				// check image exists
				var img = new Image();
				$(img).error(function(){
					showError('Error: Couldn\'t find ' + imgSrc, 'noImage');
				}).attr('src', imgSrc);
			}
		};
	};
})(jQuery);