(function($) {
    $.fn.lazyload = function(options) {
        var settings = {
            threshold: 0,
            failurelimit: 0,
            event: "scroll",
            effect: "show",
            container: window
        };
        if (options) {
            $.extend(settings, options)
        }
        var elements = this;
        if ("scroll" == settings.event) {
            $(settings.container).bind("scroll",
            function(event) {
                var counter = 0;
                elements.each(function() {
                    if ($.abovethetop(this, settings) || $.leftofbegin(this, settings)) { } else if (!$.belowthefold(this, settings) && !$.rightoffold(this, settings)) {
                        $(this).trigger("appear")
                    } else {
                        if (counter++ > settings.failurelimit) {
                            return false
                        }
                    }
                });
                var temp = $.grep(elements,
                function(element) {
                    return !element.loaded
                });
                elements = $(temp)
            })
        }
        this.each(function() {
            var self = this;
            if (undefined == $(self).attr("original")) {
                $(self).attr("original", $(self).attr("src"))
            }
            if ("scroll" != settings.event || undefined == $(self).attr("src") || '' == $(self).attr("src") || settings.placeholder == $(self).attr("src") || ($.abovethetop(self, settings) || $.leftofbegin(self, settings) || $.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
            }
            $(self).one("appear",
            function() {
                if (!this.loaded) {
                    $("<img />").bind("load",
                    function() {
                        $(self).hide().attr("src", $(self).attr("original"))[settings.effect](settings.effectspeed);
                        self.loaded = true
                    }).attr("src", $(self).attr("original"))
                }
            });
            if ("scroll" != settings.event) {
                $(self).bind(settings.event,
                function(event) {
                    if (!self.loaded) {
                        $(self).trigger("appear")
                    }
                })
            }
        });
        $(settings.container).trigger(settings.event);
        return this
    };
    $.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
    };
    $.abovethetop = function(element, settings) {
        if (settings.container === undefined || settings.container === window) {
            var fold = $(window).scrollTop()
        } else {
            var fold = $(settings.container).offset().top
        }
        return fold >= $(element).offset().top + settings.threshold + $(element).height()
    };
    $.leftofbegin = function(element, settings) {
        if (settings.container === undefined || settings.container === window) {
            var fold = $(window).scrollLeft()
        } else {
            var fold = $(settings.container).offset().left
        }
        return fold >= $(element).offset().left + settings.threshold + $(element).width()
    };
    $.extend($.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);