(() => {
  'use strict';

  const body = document.querySelector('body.home-v260');
  if (!body || window.__DBC_HOME_V260__) return;
  window.__DBC_HOME_V260__ = true;

  const root = document.documentElement;
  const reducedMotion = window.matchMedia('(prefers-reduced-motion: reduce)');
  const header = document.querySelector('.site-header');
  const progress = document.querySelector('.v260-progress');
  const progressLinks = progress
    ? Array.from(progress.querySelectorAll('a[data-v260-progress]'))
    : [];
  const sections = progressLinks
    .map((link) => ({
      id: link.dataset.v260Progress,
      link,
      section: document.getElementById(link.dataset.v260Progress)
    }))
    .filter((item) => item.section);

  function syncHeaderHeight() {
    if (!header) return;
    const height = Math.round(header.getBoundingClientRect().height);
    if (height > 0) root.style.setProperty('--dbc-header-height', `${height}px`);
  }

  syncHeaderHeight();
  if (header && 'ResizeObserver' in window) {
    const headerObserver = new ResizeObserver(syncHeaderHeight);
    headerObserver.observe(header);
  }

  let activeId = '';
  function setActive(id) {
    if (!id || id === activeId) return;
    activeId = id;
    if (progress) progress.classList.toggle('is-on-hero', id === 'home');
    sections.forEach((item) => {
      const active = item.id === id;
      item.link.classList.toggle('is-active', active);
      if (active) item.link.setAttribute('aria-current', 'location');
      else item.link.removeAttribute('aria-current');
    });
  }

  const visibility = new Map(sections.map((item) => [item.id, 0]));
  function chooseActiveSection() {
    let current = sections[0];
    let highest = -1;
    sections.forEach((item) => {
      const ratio = visibility.get(item.id) || 0;
      if (ratio > highest) {
        highest = ratio;
        current = item;
      }
    });
    if (current) setActive(current.id);
  }

  if ('IntersectionObserver' in window) {
    const activeObserver = new IntersectionObserver((entries) => {
      entries.forEach((entry) => {
        const item = sections.find((candidate) => candidate.section === entry.target);
        if (item) visibility.set(item.id, entry.isIntersecting ? entry.intersectionRatio : 0);
      });
      chooseActiveSection();
    }, {
      rootMargin: '-18% 0px -18% 0px',
      threshold: [0, .08, .18, .32, .5, .7]
    });
    sections.forEach((item) => activeObserver.observe(item.section));
  } else {
    setActive((location.hash || '#home').slice(1));
  }

  sections.forEach((item) => {
    item.link.addEventListener('click', () => setActive(item.id));
  });

  const revealSections = Array.from(document.querySelectorAll('.v260-screen'));
  function revealAll() {
    revealSections.forEach((section) => section.classList.add('is-v260-visible'));
  }

  if (reducedMotion.matches || !('IntersectionObserver' in window)) {
    revealAll();
  } else {
    body.classList.add('v260-motion-ready');
    const revealObserver = new IntersectionObserver((entries, observer) => {
      entries.forEach((entry) => {
        if (!entry.isIntersecting) return;
        entry.target.classList.add('is-v260-visible');
        observer.unobserve(entry.target);
      });
    }, {
      rootMargin: '0px 0px -12% 0px',
      threshold: .08
    });
    revealSections.forEach((section) => revealObserver.observe(section));
  }

  function handleReducedMotion(event) {
    if (!event.matches) return;
    body.classList.remove('v260-motion-ready');
    revealAll();
  }

  if (typeof reducedMotion.addEventListener === 'function') {
    reducedMotion.addEventListener('change', handleReducedMotion);
  }

  function syncParticleCaptionLanguage() {
    const english = root.dataset.lang === 'en' || root.lang.toLowerCase().startsWith('en');
    const brand = document.querySelector('.dbc-bioten-particle-caption .dbc-bioten-caption-brand');
    const text = document.querySelector('.dbc-bioten-particle-caption .dbc-bioten-caption-text');
    if (brand) {
      brand.textContent = english
        ? 'DBC · We Innovate Future Applications'
        : '世界杯竞猜官网 · 创新未来应用';
    }
    if (text) {
      text.textContent = english
        ? 'BIOTEN · Fiber-Based Food Packaging Barrier System'
        : '博碳 · 纸基食品包装阻隔工程系统';
    }
  }

  syncParticleCaptionLanguage();
  document.addEventListener('dbc:languagechange', () => {
    window.requestAnimationFrame(() => {
      syncParticleCaptionLanguage();
      chooseActiveSection();
    });
  });

  const languageObserver = new MutationObserver(() => {
    window.requestAnimationFrame(syncParticleCaptionLanguage);
  });
  languageObserver.observe(root, {
    attributes: true,
    attributeFilter: ['lang', 'data-lang']
  });
})();