/*
 * Lazy Load - jQuery plugin for lazy loading images
 *
 * Copyright (c) 2007-2013 Mika Tuupola
 *
 * Licensed under the MIT license:
 *   http://www.opensource.org/licenses/mit-license.php
 *
 * Project home:
 *   http://www.appelsiini.net/projects/lazyload
 *
 * Version:  1.8.6
 * Modified by xiaogezi v1.0.5+
 *
 */

(function ($, window, document, undefined) {
    var $window = $(window);

    $.fn.lazyload = function (options) {
        var elements = this;
        var $container;
        var settings = {
            threshold: 0,
            failure_limit: 0,
            event: "scroll",
            effect: "show",
            container: window,
            data_attribute: "src",
            skip_invisible: true,
            appear: null,
            load: null,
            placeholder: "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAAXNSR0IArs4c6QAAAARnQU1BAACxjwv8YQUAAAAJcEhZcwAADsQAAA7EAZUrDhsAAAANSURBVBhXYzh8+PB/AAffA0nNPuCLAAAAAElFTkSuQmCC"
        };

        function update() {
            var counter = 0;

            elements.each(function () {
                var $this = $(this);
                if (settings.skip_invisible && $this.css("display") === "none") {
                    return;
                }
                if ($.abovethetop(this, settings) ||
                    $.leftofbegin(this, settings)) {
                    /* Nothing. */
                } else if (!$.belowthefold(this, settings) &&
                    !$.rightoffold(this, settings)) {
                    $this.trigger("appear");
                    /* if we found an image we'll load, reset the counter */
                    counter = 0;
                } else {
                    if (++counter > settings.failure_limit) {
                        return false;
                    }
                }
            });

        }

        if (options) {
            /* Maintain BC for a couple of versions. */
            if (undefined !== options.failurelimit) {
                options.failure_limit = options.failurelimit;
                delete options.failurelimit;
            }
            if (undefined !== options.effectspeed) {
                options.effect_speed = options.effectspeed;
                delete options.effectspeed;
            }

            $.extend(settings, options);
        }

        /* Cache container as jQuery as object. */
        $container = (settings.container === undefined ||
            settings.container === window) ? $window : $(settings.container);

        /* Fire one scroll event per scroll. Not one scroll event per image. */
        if (0 === settings.event.indexOf("scroll")) {
            $container.on(settings.event, function (event) {
                return update();
            });
        }

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

            self.loaded = false;

            /* If no src attribute given use data:uri. */
            if ($self.attr("src") === undefined || $self.attr("src") === false) {
                if ($self.is("img")) {
                    $self.attr("src", settings.placeholder);
                }
            }

            /* When appear is triggered load original image. */
            $self.one("appear", function () {
                if (!this.loaded) {
                    if (settings.appear) {
                        var elements_left = elements.length;
                        settings.appear.call(self, elements_left, settings);
                    }

                    if (!$self.is('[data-class]')) { //xiaogezi
                        var original = $self.data(settings.data_attribute);

                        $("<img />")
                            .on("load", function () {
                                settings.effect !== false && $self.hide()

                                if ($self.is("img")) {
                                    $self.attr("src", original);
                                } else {
                                    $self.css('background-image', 'url(' + original + ')');
                                }
                                var fn = $self[settings.effect];
                                fn && fn(settings.effect_speed);
                                self.loaded = true;

                                $self.trigger('appeared');
                                $self.removeAttr('data-src');

                                /* Remove image from array so it is not looped next time. */
                                var temp = $.grep(elements, function (element) {
                                    return !element.loaded;
                                });
                                elements = $(temp);

                                if (settings.load) {
                                    var elements_left = elements.length;
                                    settings.load.call(self, elements_left, settings);
                                }
                            })
                            .attr("src", original);
                    } else { //xiaogezi
                        var cssclass = $self.data('class');
                        settings.effect == 'hide' && $self.hide();
                        $self.addClass(cssclass).removeAttr('data-class');
                        self.loaded = true;
                        $self.trigger('appeared');
                    }
                }
            });

            /* When wanted event is triggered load original image */
            /* by triggering appear.                              */
            if (0 !== settings.event.indexOf("scroll")) {
                $self.on(settings.event, function (event) {
                    if (!self.loaded) {
                        $self.trigger("appear");
                    }
                });
            }
        });

        /* Check if something appears when window is resized. */
        $window.on("resize", function (event) {
            update();
        });

        /* With IOS5 force loading images when navigating with back button. */
        /* Non optimal workaround. */
        if ((/iphone|ipod|ipad.*os 5/gi).test(navigator.appVersion)) {
            $window.on("pageshow", function (event) {
                // if (event.originalEvent.persisted) {
                event = event.originalEvent || event;
                if (event.persisted) {
                    elements.each(function () {
                        $(this).trigger("appear");
                    });
                }
            });
        }

        /* Force initial check if images should appear. */
        $(window).on("load", function () {
            update();
        });

        return this;
    };

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

    $.belowthefold = function (element, settings) {
        var fold;

        if (settings.container === undefined || settings.container === window) {
            fold = $window.height() + $window[0].scrollY;
        } else {
            fold = $(settings.container).offset().top + $(settings.container).height();
        }

        return fold <= $(element).offset().top - settings.threshold;
    };

    $.rightoffold = function (element, settings) {
        var fold;

        if (settings.container === undefined || settings.container === window) {
            fold = $window.width() + $window[0].scrollX;
        } else {
            fold = $(settings.container).offset().left + $(settings.container).width();
        }

        return fold <= $(element).offset().left - settings.threshold;
    };

    $.abovethetop = function (element, settings) {
        var fold;

        if (settings.container === undefined || settings.container === window) {
            fold = $window[0].scrollY;
        } else {
            fold = $(settings.container).offset().top;
        }

        return fold >= $(element).offset().top + settings.threshold + $(element).height();
    };

    $.leftofbegin = function (element, settings) {
        var fold;

        if (settings.container === undefined || settings.container === window) {
            fold = $window[0].scrollX;
        } else {
            fold = $(settings.container).offset().left;
        }

        return fold >= $(element).offset().left + settings.threshold + $(element).width();
    };

    $.inviewport = function (element, settings) {
        return !$.rightoffold(element, settings) && !$.leftofbegin(element, settings) &&
            !$.belowthefold(element, settings) && !$.abovethetop(element, settings);
    };

    /* Custom selectors for your convenience.   */
    /* Use as $("img:below-the-fold").something() or */
    /* $("img").filter(":below-the-fold").something() which is faster */

    $.extend($.fn, {
        "below-the-fold": function (a) { return $.belowthefold(a, { threshold: 0 }); },
        "above-the-top": function (a) { return !$.belowthefold(a, { threshold: 0 }); },
        "right-of-screen": function (a) { return $.rightoffold(a, { threshold: 0 }); },
        "left-of-screen": function (a) { return !$.rightoffold(a, { threshold: 0 }); },
        "in-viewport": function (a) { return $.inviewport(a, { threshold: 0 }); },
        /* Maintain BC for couple of versions. */
        "above-the-fold": function (a) { return !$.belowthefold(a, { threshold: 0 }); },
        "right-of-fold": function (a) { return $.rightoffold(a, { threshold: 0 }); },
        "left-of-fold": function (a) { return !$.rightoffold(a, { threshold: 0 }); }
    });

})(window.Zepto || window.jQuery, window, document);
