/**
 * LazyAction - jQuery plugin for lazy action
 * 
 * @author Takeo Tamura
 * 
 * LazyAction is inspired by Lazyloader
 * http://www.appelsiini.net/projects/lazyload
 * 
 * 
 * function callbackFunction(target,options){
 * 	
 * }
 * 
 * var options={aaa:1,bbb:2};
 * 
 * $(xxxx).lazyaction(action:callbackFunction,options:options);
 */
(function($) {

    $.fn.lazyaction = function(options) {
        var settings = {
            threshold    : 0,
            failurelimit : 0,
            event        : "scroll",
            container    : window,
			action:null,
			options:null
        };

        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)) {

                    	//見えていなければ
                    	$(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.appeared;
                });
                elements = $(temp);
            });
        }

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


            /* When appear is triggered load original image. */
            $(self).one("appear", function() {
                if (!this.appeared) {
                	//$(self).css("color","#FF0000");
					settings.action(self,settings.options);
					
                	self.appeared = true;
                };
            });





            /* TODO: use .data() instead of .attr() */
            //$(self).attr("original", $(self).attr("src"));
            if ("scroll" != settings.event
                         || $.belowthefold(self, settings)
                         || $.rightoffold(self, settings)) {
            	//表示されていない場合
                self.appeared = false;
            } else {

            	//表示されてる場合
            	 self.appeared = false;
                $(self).trigger("appear");
            }



            /* When wanted event is triggered load original image */
            /* by triggering appear.                              */
            if ("scroll" != settings.event) {
                $(self).bind(settings.event, function(event) {
                    if (!self.appeared) {
                        $(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);