/*
 * Lazy Load - jQuery plugin for lazy loading images
 *
 * Copyright (c) 2007 Mika Tuupola
 *
 * Licensed under the MIT license:
 *   http://www.opensource.org/licenses/mit-license.php
 *
 * Revision: $Id$
 *
 */
(function($) {
    
    $.fn.lazyload = function(options) {
        var settings = {
            threshold : 0
        };
                
        if(options) {
            $.extend(settings, options);
        };

        return this.each(function() {
            var self = this;
        
            /* TODO: why to use attr? Possible memory leak. */
            $(self).attr("original", $(self).attr("src"));
            if (settings.event || $.belowthefold(self, settings) 
                               || $.rightoffold(self, settings)) {
                if (settings.placeholder) {
                    $(self).attr("src", settings.placeholder);                    
                } else {
                    $(self).removeAttr("src");
                }
                self.loaded = false;
            } else {
                self.loaded = true;
            }

            if (settings.event) {
                $(self)[settings.event](function(event) {
                    if (!self.loaded) {
                        $(self).attr("src", $(self).attr("original"));   
                        self.loaded = true;
                    };
                });
            } else {
                $(window).bind("scroll", function(event) {
                    if (!self.loaded && !$.belowthefold(self, settings) 
                                     && !$.rightoffold(self, settings)) {
                        $(self).attr("src", $(self).attr("original"));   
                        self.loaded = true;  
                    };
                });                
            };
        });
    };

    /* Convenience methods in jQuery namespace.           */
    /* Use as  $.belowthefold(element, {threshold : 100}) */

    $.belowthefold = function(element, settings) {
        var fold = $(window).height() + $(window).scrollTop();
        return fold <= $(element).offset().top - settings.threshold;
    }
    
    $.rightoffold = function(element, settings) {
        var fold = $(window).width() + $(window).scrollLeft();
        return fold <= $(element).offset().left - settings.threshold;
    }
    
    /* Custom selectors for your convenience.   */
    /* Use as $("img:belowthefold").something() */

    $.extend($.expr[':'], {
        belowthefold : "$.belowthefold(a, {threshold : 0})",
        abovethefold : "!$.belowthefold(a, {threshold : 0})",
        rightoffold  : "$.rightoffold(a,  {threshold : 0})",
        leftoffold   : "!$.rightoffold(a,   {threshold : 0})"
    });
    
})(jQuery);