/* 东燊科技 Donsen — 交互脚本 */
(function () {
  'use strict';

  /* ---------- 语言切换（默认中文，记忆选择） ---------- */
  var body = document.body;
  var toggle = document.getElementById('langToggle');
  var optZh = document.querySelector('.lang-zh');
  var optEn = document.querySelector('.lang-en');

  function applyLang(lang) {
    body.setAttribute('data-lang', lang);
    document.documentElement.setAttribute('lang', lang === 'zh' ? 'zh-CN' : 'en');
    if (optZh) optZh.classList.toggle('is-active', lang === 'zh');
    if (optEn) optEn.classList.toggle('is-active', lang === 'en');
    try { localStorage.setItem('donsen-lang', lang); } catch (e) {}
  }

  var params = new URLSearchParams(location.search);
  var saved = null;
  try { saved = params.get('lang') || localStorage.getItem('donsen-lang'); } catch (e) {}
  applyLang(saved === 'en' ? 'en' : 'zh');

  if (toggle) {
    toggle.addEventListener('click', function () {
      applyLang(body.getAttribute('data-lang') === 'zh' ? 'en' : 'zh');
    });
  }

  /* ---------- 移动端菜单 ---------- */
  var burger = document.getElementById('navBurger');
  var links = document.getElementById('navLinks');
  if (burger && links) {
    burger.addEventListener('click', function () {
      links.classList.toggle('open');
    });
    links.querySelectorAll('a').forEach(function (a) {
      a.addEventListener('click', function () { links.classList.remove('open'); });
    });
  }

  /* ---------- 滚动高亮导航（rAF 节流 + offsetTop 缓存，滚动帧内零强制布局） ---------- */
  var navEl = document.getElementById('nav');
  var sections = Array.prototype.slice.call(document.querySelectorAll('section[id]'));
  var navLinks = Array.prototype.slice.call(document.querySelectorAll('.nav-link'));
  var sectionTops = [];
  function measureTops() {
    sectionTops = sections.map(function (s) { return s.getBoundingClientRect().top + window.scrollY; });
  }
  var scrollTick = false;
  function onScrollFrame() {
    scrollTick = false;
    var y = window.scrollY;
    var scrolled = y > 40;
    if (navEl) {
      navEl.style.background = scrolled ? 'rgba(6,15,34,.96)' : 'rgba(6,15,34,.82)';
      // 滚动后切纯色背景并去掉毛玻璃（backdrop-filter 持续混合开销大）
      navEl.classList.toggle('scrolled', scrolled);
    }
    var current = sections[0] ? sections[0].id : '';
    for (var i = 0; i < sectionTops.length; i++) {
      if (sectionTops[i] <= y + 120) current = sections[i].id;
    }
    navLinks.forEach(function (l) {
      l.classList.toggle('active', l.getAttribute('href') === '#' + current);
    });
  }
  function onScroll() {
    if (scrollTick) return;
    scrollTick = true;
    requestAnimationFrame(onScrollFrame);
  }
  measureTops();
  window.addEventListener('scroll', onScroll, { passive: true });
  window.addEventListener('resize', function () { measureTops(); onScrollFrame(); });
  onScrollFrame();

  /* ---------- 滚动显现动画（?static=1 或减弱动效时直接全展） ---------- */
  var revealEls = document.querySelectorAll('.reveal');
  var staticMode = new URLSearchParams(location.search).get('static') === '1';
  var reduceMotion = window.matchMedia && window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (staticMode || reduceMotion || !('IntersectionObserver' in window)) {
    revealEls.forEach(function (el) { el.classList.add('in'); });
  } else {
    var io = new IntersectionObserver(function (entries) {
      entries.forEach(function (en) {
        if (en.isIntersecting) {
          en.target.classList.add('in');
          io.unobserve(en.target);
        }
      });
    }, { threshold: 0.12 });
    revealEls.forEach(function (el) { io.observe(el); });
  }

  /* ---------- 页脚年份 ---------- */
  var y = new Date().getFullYear();
  ['year', 'year-en'].forEach(function (id) {
    var el = document.getElementById(id);
    if (el) el.textContent = y;
  });
})();