/* global window, document */

(function () {
  'use strict';

  var Luxtools = window.Luxtools || (window.Luxtools = {});

  // ============================================================
  // Gallery Thumbnails Module
  // ============================================================
  Luxtools.GalleryThumbnails = (function () {
    function loadThumb(img) {
      var src = img.getAttribute('data-thumb-src') || '';
      if (!src) return;
      if (img.getAttribute('data-thumb-loading') === '1') return;
      img.setAttribute('data-thumb-loading', '1');

      var pre = new window.Image();
      pre.onload = function () {
        img.src = src;
        img.removeAttribute('data-thumb-src');
        img.removeAttribute('data-thumb-loading');
      };
      pre.onerror = function () {
        img.removeAttribute('data-thumb-loading');
      };
      pre.src = src;
    }

    function init() {
      var imgs = document.querySelectorAll('div.luxtools-gallery img[data-thumb-src]');
      if (!imgs || !imgs.length) return;

      if ('IntersectionObserver' in window) {
        var io = new window.IntersectionObserver(function (entries) {
          entries.forEach(function (entry) {
            if (!entry.isIntersecting) return;
            loadThumb(entry.target);
            io.unobserve(entry.target);
          });
        }, { rootMargin: '200px' });

        imgs.forEach(function (img) { io.observe(img); });
      } else {
        // Fallback: load soon after initial render
        window.setTimeout(function () {
          imgs.forEach(loadThumb);
        }, 0);
      }
    }

    return {
      init: init
    };
  })();
})();