(function($) {

    $.fn.PagingLoadHidden = function(url, isLazyload, callback, options) {
        if ( typeof url != "string" ) {
            isLazyload = url;
            url = null;
        }       
        
        if( typeof isLazyload != "boolean" )
        {
            callback = isLazyload;
            isLazyload = true;
        }
        
        if ( typeof callback == "object" )
        {
            options = callback;
            callback = null;
        }

        
        var settings = {
            threshold    : 0,
            failurelimit : 0,
            event        : "scroll",
            effect       : "show",
            container    : window,
            beforeLoading : null, 
            complete     : callback,
            replaceElement : true
        };
                
        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") || 
                    settings.placeholder == $(self).attr("src") || 
                    ($.abovethetop(self, settings) ||
                     $.leftofbegin(self, settings) || 
                     $.belowthefold(self, settings) || 
                     $.rightoffold(self, settings) )) {
     
                self.loaded = false;
            } else {
                self.loaded = true;
            }
            

            $(self).one("appear", function() {
                if (!this.loaded) {
                    
                    if( $.isFunction(settings.beforeLoading) )
                        settings.beforeLoading();
                    
                    if( typeof url != "string" )
                    {
                        if( $.isFunction(settings.complete) )
                            settings.complete();
                    }
                    else
                    {
						if( settings.replaceElement )
						{
							$.get(url, function(data, textStatus) {
								$(self).replaceWith(data);
								if( $.isFunction(settings.complete) )
									settings.complete();
							}); 
						}
						else
						{
							$(self).load(url, function() {
								if( $.isFunction(settings.complete) )
									settings.complete();
							});
						}
                    }
                }
            });
                              
            if ("scroll" != settings.event) {
                $(self).bind(settings.event, function(event) {
                    if (!self.loaded) {
                        $(self).trigger("appear");
                    }
                });
            }
            

            if( !isLazyload )
            {
                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);