/*
 * Lazy Load - jQuery plugin for lazy loading images
 *
 * Copyright (c) 2007-2009 Mika Tuupola
 *
 * Licensed under the MIT license:
 *   http://www.opensource.org/licenses/mit-license.php
 *
 * Project home:
 *   http://www.appelsiini.net/projects/lazyload
 *
 * Version:  1.4.0
 *
 */
(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;
            /* TODO: use .data() instead of .attr() */
            $(self).attr("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).attr("original"))[settings.effect](settings.effectspeed);
                        self.loaded = true;
                    }).attr("src", $(self).attr("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);