(function($) {

    $.extend({
        add2cart: function(source_id, target_id, callback) {

            var source = $('#' + source_id);
            var target = $('#' + target_id);

            var shadow = $('#' + source_id + '_shadow');
            if (!shadow.attr('id')) {
                $('body').prepend('<div id="' + source.attr('id') + '_shadow" style="display: none; background-color: #ddd; border: solid 1px darkgray; position: static; top: 0px; z-index: 100000;">&nbsp;</div>');
                var shadow = $('#' + source.attr('id') + '_shadow');
            }

            if (!shadow) {
                alert('Cannot create the shadow div');
            }

            shadow.width(source.css('width')).height(source.css('height')).css('top', source.offset().top).css('left', source.offset().left).css('opacity', 0.5).show();
            shadow.css('position', 'absolute');

            shadow.animate({ width: target.innerWidth(), height: target.innerHeight(), top: target.offset().top, left: target.offset().left }, { duration: 300 })
            .animate({ opacity: 0 }, { duration: 100, complete: function() {
                $('#sampleCart_shadow').remove();
                $('#' + source_id + '_shadow').remove();
                $('#undefined_shadow').remove();
            }
            });

        }
    });
})(jQuery);