/*
* 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:  1.5.0
*
*/
(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 ($.abovethetop(this, settings) ||
                        $.leftofbegin(this, settings)) {
                        /* Nothing. */
                    } else if (!$.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);
            });
        }

        this.each(function() {
            var self = this;

            /* Save original only if it is not defined in HTML. */
            if (undefined == $(self).attr("original")) {
                $(self).attr("original", $(self).attr("src"));
            }

            if ("scroll" != settings.event ||
                    undefined == $(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;
            }

            /* 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");
                    }
                });
            }
        });

        /* Force initial check if images should appear. */
        $(settings.container).trigger(settings.event);

        return this;

    };

    /* 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;
    };

    $.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();
    };
    /* 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);