/*

 * Lazy Load - jQuery plugin for lazy loading images

 *

 * Copyright (c) 2007-2012 Mika Tuupola

 *

 * Licensed under the MIT license:

 *   http://www.opensource.org/licenses/mit-license.php

 *

 * Project home:

 *   http://www.appelsiini.net/projects/lazyload

 *

 * Version:  1.7.1

 *

 */

(function($, window) {



    $window = $(window);



    $.fn.lazyload = function(options) {

        var elements = this;

        var settings = {

            threshold       : 0,

            failure_limit   : 0,

            event           : "scroll",

            effect          : "show",

            container       : window,

            data_attribute  : "original",

            skip_invisible  : true,

            appear          : null,

            load            : null

        };



        update = function() {

            var counter = 0;

      

            elements.each(function() {

                var $this = $(this);

                if (settings.skip_invisible && !$this.is(":visible")) {

                    return;

                }

                if ($.abovethetop(this, settings) ||

                    $.leftofbegin(this, settings)) {

                        /* Nothing. */

                } else if (!$.belowthefold(this, settings) &&

                    !$.rightoffold(this, settings)) {

                        $this.trigger("appear");

                } 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.bind(settings.event, function(event) {

                return update();

            });

        }



        this.each(function() {

            var self = this;

            var $self = $(self);



            self.loaded = false;



            /* 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);

                    }

                    $("<img />")

                        .bind("load", function() {

                            $self

                                .hide()

                                .attr("src", $self.data(settings.data_attribute))

                                [settings.effect](settings.effect_speed);

                            self.loaded = true;



                            /* 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", $self.data(settings.data_attribute));

                }

            });



            /* When wanted event is triggered load original image */

            /* by triggering appear.                              */

            if (0 !== settings.event.indexOf("scroll")) {

                $self.bind(settings.event, function(event) {

                    if (!self.loaded) {

                        $self.trigger("appear");

                    }

                });

            }

        });



        /* Check if something appears when window is resized. */

        $window.bind("resize", function(event) {

            update();

        });



        /* Force initial check if images should appear. */

        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.scrollTop();

        } else {

            fold = $container.offset().top + $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.scrollLeft();

        } else {

            fold = $container.offset().left + $container.width();

        }



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

    };

        

    $.abovethetop = function(element, settings) {

        var fold;

        

        if (settings.container === undefined || settings.container === window) {

            fold = $window.scrollTop();

        } else {

            fold = $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.scrollLeft();

        } else {

            fold = $container.offset().left;

        }



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

    };



    $.inviewport = function(element, settings) {

         return !$.rightofscreen(element, settings) && !$.leftofscreen(element, settings) && 

                !$.belowthefold(element, settings) && !$.abovethetop(element, settings);

     };



    /* Custom selectors for your convenience.   */

    /* Use as $("img:below-the-fold").something() */



    $.extend($.expr[':'], {

        "below-the-fold" : function(a) { return $.belowthefold(a, {threshold : 0, container: window}); },

        "above-the-top"  : function(a) { return !$.belowthefold(a, {threshold : 0, container: window}); },

        "right-of-screen": function(a) { return $.rightoffold(a, {threshold : 0, container: window}); },

        "left-of-screen" : function(a) { return !$.rightoffold(a, {threshold : 0, container: window}); },

        "in-viewport"    : function(a) { return !$.inviewport(a, {threshold : 0, container: window}); },

        /* Maintain BC for couple of versions. */

        "above-the-fold" : function(a) { return !$.belowthefold(a, {threshold : 0, container: window}); },

        "right-of-fold"  : function(a) { return $.rightoffold(a, {threshold : 0, container: window}); },

        "left-of-fold"   : function(a) { return !$.rightoffold(a, {threshold : 0, container: window}); }

    });



})(jQuery, window);