(function ($) {
    var defaults = {
        showTime: 800,
        offsetBottom: 0,
        offsetTopm: 50,
        onLoadBackEnd: function (index, dom) { },
        onLoadBackStart: function (index, dom) { }
    };

    var $lazyImgList = $();

    function checkOffset() {
        var scrollTop = $(document).scrollTop();
        var windowHeight = $(window).height();

        $lazyImgList.each(function (index) {
            var $dom = $(this);
            if ($dom.attr("data-comp")) return; // Already processed

            var offsetTop = $dom.offset().top;
            // Check if image is in viewport (with some buffer)
            if (offsetTop - scrollTop + defaults.offsetTopm >= 0 && 
                offsetTop - scrollTop < (windowHeight + defaults.offsetBottom)) {
                
                showImg($dom, index);
            }
        });
    }

    function showImg($dom, index) {
        $dom.attr("data-comp", "true");
        var src = $dom.attr("data-lazy-src");
        
        defaults.onLoadBackStart(index, $dom);
        
        // Create a temporary image to preload
        var temp = new Image();
        temp.onload = function() {
            // Prepare for transition
            $dom.css({
                "opacity": 0,
                "transition": "opacity " + (defaults.showTime / 1000) + "s ease-in-out"
            });
            
            // Swap source
            $dom.attr("src", src);
            
            // Force reflow to ensure transition triggers
            void $dom[0].offsetWidth; 
            
            // Fade in
            $dom.css("opacity", 1);
            
            defaults.onLoadBackEnd(index, $dom);
        };
        temp.onerror = function() {
            // On error, show anyway (maybe broken image icon) but ensure visible
            $dom.attr("src", src);
            $dom.css("opacity", 1);
        };
        temp.src = src;
    }

    function init(setting) {
        defaults = $.extend(defaults, setting);
        
        // Auto-convert standard images to lazy load format
        // Exclude .blog-img (Header Avatar) to prevent visibility issues
        $("img").not(".blog-img").each(function() {
            var $this = $(this);
            // Only convert if not already converted and has a src
            if (!$this.attr("data-lazy-src") && $this.attr("src")) {
                $this.attr("data-lazy-src", $this.attr("src"));
                // Set placeholder
                $this.attr("src", "data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==");
            }
        });

        $lazyImgList = $("img[data-lazy-src]");
        
        checkOffset();
        
        // Debounced scroll handler could be better, but sticking to simple binding for now
        $(window).off("scroll.lazy").on("scroll.lazy resize.lazy", function() {
            checkOffset();
        });
    }

    function tryAgain() {
        // Re-initialize for new content
        init(defaults);
    }

    window.lazyLoadInit = init;
    window.lazyLoadAgain = tryAgain;

})(jQuery);