/*
* Lazy Load - jQuery plugin for lazy loading images
*
* Copyright (c) 2007-2008 Mika Tuupola
*
* Licensed under the MIT license:
* http://www.opensource.org/licenses/mit-license.php
*
* Project home:
* http://www.appelsiini.net/projects/lazyload
*
* Revision: $Id$
* Version: 1.3.1
*
*/
(function($) {
 
    $.fn.lazyload = function(options) {
        var settings = {
            threshold : 0,
            failurelimit : 0,
            event : "scroll",
            effect : "show",
            container : window
        };
                
        if(options) {
            $.extend(settings, options);
        }
 
        /* Fire one scroll event per scroll. Not one scroll event per image. */
        var elements = this;
        if ("scroll" == settings.event) {
            $(settings.container).bind("scroll", function(event) {
                var counter = 0;
                elements.each(function() {
                    if (!$.belowthefold(this, settings) &&
                        !$.rightoffold(this, settings)) {
                            $(this).trigger("appear");
                    } else {
                        if (counter++ > settings.failurelimit) {
                            return false;
                        }
                    }
                });
                /* Remove image from array so it is not looped next time. */
                var temp = $.grep(elements, function(element) {
                    return !element.loaded;
                });
                elements = $(temp);
            });
        }
        
        return this.each(function() {
            var self = this;
            $(self).data("original", $(self).attr("src"));
            if ("scroll" != 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;
            }
            
            /* When appear is triggered load original image. */
            $(self).one("appear", function() {
                if (!this.loaded) {
                    $("<img />")
                        .bind("load", function() {
                            $(self)
                                .hide()
                                .attr("src", $(self).data("original"))
                                [settings.effect](settings.effectspeed);
                            self.loaded = true;
                        })
                        .attr("src", $(self).data("original"));
                };
            });
 
            /* When wanted event is triggered load original image */
            /* by triggering appear. */
            if ("scroll" != settings.event) {
                $(self).bind(settings.event, function(event) {
                    if (!self.loaded) {
                        $(self).trigger("appear");
                    }
                });
            }
        });
 
    };
 
    /* Convenience methods in jQuery namespace. */
    /* Use as $.belowthefold(element, {threshold : 100, container : window}) */
 
    $.belowthefold = function(element, settings) {
        if (settings.container === undefined || settings.container === window) {
            var fold = $(window).height() + $(window).scrollTop();
        }
        else {
            var fold = $(settings.container).offset().top + $(settings.container).height();
        }
        return fold <= $(element).offset().top - settings.threshold;
    };
    
    $.rightoffold = function(element, settings) {
        if (settings.container === undefined || settings.container === window) {
            var fold = $(window).width() + $(window).scrollLeft();
        }
        else {
            var fold = $(settings.container).offset().left + $(settings.container).width();
        }
        return fold <= $(element).offset().left - settings.threshold;
    };
    
    /* Custom selectors for your convenience. */
    /* Use as $("img:below-the-fold").something() */
 
    $.extend($.expr[':'], {
        "below-the-fold" : "$.belowthefold(a, {threshold : 0, container: window})",
        "above-the-fold" : "!$.belowthefold(a, {threshold : 0, container: window})",
        "right-of-fold" : "$.rightoffold(a, {threshold : 0, container: window})",
        "left-of-fold" : "!$.rightoffold(a, {threshold : 0, container: window})"
    });
    
})(jQuery);