/* campus-glow 皮肤包脚本：顶条日期 + 首页轮播 + 线上展厅画廊翻页 + 返回顶部，无任何外部依赖 */
(function () {
  /* 顶条日期（本地时间，YYYY年M月D日 星期X） */
  var dateEl = document.getElementById('siteDate');
  if (dateEl) {
    var now = new Date();
    var week = ['日', '一', '二', '三', '四', '五', '六'][now.getDay()];
    dateEl.textContent = now.getFullYear() + '年' + (now.getMonth() + 1) + '月'
      + now.getDate() + '日 星期' + week;
  }

  /* 首页轮播 */
  (function () {
    var root = document.querySelector('.cg-banner');
    if (!root) return;
    var slides = root.querySelectorAll('.cg-banner-slide');
    var dots = root.querySelectorAll('.cg-banner-dots button');
    var prevBtn = root.querySelector('.cg-banner-arrow.prev');
    var nextBtn = root.querySelector('.cg-banner-arrow.next');
    if (!slides.length) return;
    var current = 0;
    var timer = null;
    var INTERVAL = 5000;

    function show(index) {
      slides[current].classList.remove('active');
      if (dots[current]) dots[current].classList.remove('active');
      current = (index + slides.length) % slides.length;
      slides[current].classList.add('active');
      if (dots[current]) dots[current].classList.add('active');
    }
    function start() {
      stop();
      if (slides.length > 1) timer = window.setInterval(function () { show(current + 1); }, INTERVAL);
    }
    function stop() {
      if (timer) { window.clearInterval(timer); timer = null; }
    }

    dots.forEach(function (dot, index) {
      dot.addEventListener('click', function () { show(index); start(); });
    });
    if (prevBtn) prevBtn.addEventListener('click', function () { show(current - 1); start(); });
    if (nextBtn) nextBtn.addEventListener('click', function () { show(current + 1); start(); });
    root.addEventListener('mouseenter', stop);
    root.addEventListener('mouseleave', start);
    root.addEventListener('focusin', stop);
    root.addEventListener('focusout', start);
    start();
  })();

  /* 线上展厅画廊：按页翻动（每页 = 当前列数），到尾页回卷 */
  (function () {
    var stage = document.querySelector('.cg-gallery-stage');
    if (!stage) return;
    var track = stage.querySelector('.cg-gallery-track');
    var items = track ? track.children : [];
    var prevBtn = stage.querySelector('.cg-gallery-arrow.prev');
    var nextBtn = stage.querySelector('.cg-gallery-arrow.next');
    if (!track || items.length < 1) return;
    var page = 0;
    var timer = null;
    var INTERVAL = 4500;

    function perView() {
      var w = window.innerWidth;
      if (w <= 640) return 1;
      if (w <= 992) return 2;
      return parseInt(stage.getAttribute('data-cols') || '4', 10) || 4;
    }
    function pages() {
      return Math.max(1, Math.ceil(items.length / perView()));
    }
    function update() {
      if (page >= pages()) page = 0;
      if (page < 0) page = pages() - 1;
      track.style.transform = 'translateX(-' + (page * 100) + '%)';
    }
    function start() {
      stop();
      if (pages() > 1) {
        timer = window.setInterval(function () { page++; update(); }, INTERVAL);
      }
    }
    function go(delta) { page += delta; update(); start(); }
    function stop() {
      if (timer) { window.clearInterval(timer); timer = null; }
    }

    if (prevBtn) prevBtn.addEventListener('click', function () { go(-1); });
    if (nextBtn) nextBtn.addEventListener('click', function () { go(1); });
    stage.addEventListener('mouseenter', stop);
    stage.addEventListener('mouseleave', start);
    window.addEventListener('resize', function () { page = 0; update(); });

    update();
    start();
  })();

  /* 返回顶部：滚动一屏后出现，点击平滑回顶 */
  (function () {
    var btn = document.querySelector('.cg-backtop');
    if (!btn) return;
    function toggle() {
      if (window.scrollY > window.innerHeight * 0.6) {
        btn.classList.add('visible');
      } else {
        btn.classList.remove('visible');
      }
    }
    window.addEventListener('scroll', toggle, { passive: true });
    btn.addEventListener('click', function () {
      window.scrollTo({ top: 0, behavior: 'smooth' });
    });
    toggle();
  })();
})();