(function () {
  'use strict';

  document.documentElement.classList.add('js');

  var state = {
    language: 'zh',
    releases: [],
    filter: 'all'
  };

  var languageToggle = document.querySelector('[data-language-toggle]');
  var languageCurrent = document.querySelector('[data-language-current]');
  var languageNext = document.querySelector('[data-language-next]');
  var navToggle = document.querySelector('[data-nav-toggle]');
  var primaryNav = document.querySelector('[data-primary-nav]');
  var releaseGrid = document.querySelector('[data-release-grid]');
  var releaseEmpty = document.querySelector('[data-release-empty]');
  var releaseFilters = document.querySelector('[data-release-filters]');

  function readSavedLanguage() {
    try {
      return localStorage.getItem('dbc-site-language') === 'en' ? 'en' : 'zh';
    } catch (error) {
      return 'zh';
    }
  }

  function saveLanguage(language) {
    try {
      localStorage.setItem('dbc-site-language', language);
    } catch (error) {
      return;
    }
  }

  function translated(entry, key) {
    var suffix = state.language === 'en' ? 'En' : 'Zh';
    return entry[key + suffix] || entry[key + 'Zh'] || '';
  }

  function applyLanguage(language) {
    state.language = language === 'en' ? 'en' : 'zh';
    document.documentElement.lang = state.language === 'en' ? 'en' : 'zh-CN';
    document.documentElement.dataset.lang = state.language;

    document.querySelectorAll('[data-zh][data-en]').forEach(function (node) {
      node.textContent = node.getAttribute(state.language === 'en' ? 'data-en' : 'data-zh');
    });

    document.querySelectorAll('[data-label-zh][data-label-en]').forEach(function (node) {
      node.setAttribute('aria-label', node.getAttribute(state.language === 'en' ? 'data-label-en' : 'data-label-zh'));
    });

    document.querySelectorAll('[data-alt-zh][data-alt-en]').forEach(function (node) {
      node.setAttribute('alt', node.getAttribute(state.language === 'en' ? 'data-alt-en' : 'data-alt-zh'));
    });

    if (languageCurrent && languageNext) {
      languageCurrent.textContent = state.language === 'en' ? 'EN' : '中';
      languageNext.textContent = state.language === 'en' ? '中' : 'EN';
    }

    if (languageToggle) {
      languageToggle.setAttribute('aria-label', state.language === 'en' ? '切换到中文' : 'Switch to English');
    }

    document.title = state.language === 'en'
      ? 'BIOTEN PHA Waterborne Varnish | Paper Packaging Surface Engineering'
      : '博碳PHA水性光油｜纸包装表面工程产品系统';

    renderReleases();
    saveLanguage(state.language);
  }

  function closePrimaryNav() {
    if (!primaryNav || !navToggle) return;
    primaryNav.classList.remove('is-open');
    navToggle.setAttribute('aria-expanded', 'false');
    document.body.classList.remove('nav-open');
  }

  function togglePrimaryNav() {
    if (!primaryNav || !navToggle) return;
    var open = !primaryNav.classList.contains('is-open');
    primaryNav.classList.toggle('is-open', open);
    navToggle.setAttribute('aria-expanded', String(open));
    document.body.classList.toggle('nav-open', open);
  }

  function escapeText(value) {
    return String(value || '')
      .replace(/&/g, '&')
      .replace(/</g, '<')
      .replace(/>/g, '>')
      .replace(/"/g, '"')
      .replace(/'/g, ''');
  }

  function formatDate(value) {
    if (!/^\d{4}-\d{2}-\d{2}$/.test(value || '')) return '';
    if (state.language === 'en') {
      var date = new Date(value + 'T00:00:00');
      return new Intl.DateTimeFormat('en', { year: 'numeric', month: 'short', day: '2-digit' }).format(date);
    }
    return value.replace(/-/g, '.');
  }

  function releaseCard(entry) {
    var featured = entry.featured ? ' is-featured' : '';
    var title = escapeText(translated(entry, 'title'));
    var summary = escapeText(translated(entry, 'summary'));
    var label = escapeText(translated(entry, 'label'));
    var action = state.language === 'en' ? 'Open record' : '查看记录';
    var imageAlt = title;

    return [
      '<a class="release-card' + featured + '" href="' + escapeText(entry.href) + '">',
      '  <span class="release-card__media"><img src="' + escapeText(entry.image) + '" loading="lazy" decoding="async" alt="' + imageAlt + '"></span>',
      '  <span class="release-card__body">',
      '    <span class="release-card__meta"><span>' + label + '</span><time datetime="' + escapeText(entry.date) + '">' + formatDate(entry.date) + '</time></span>',
      '    <h3>' + title + '</h3>',
      '    <p>' + summary + '</p>',
      '    <span class="release-card__action">' + action + '</span>',
      '  </span>',
      '</a>'
    ].join('');
  }

  function renderReleases() {
    if (!releaseGrid || !state.releases.length) return;

    var entries = state.releases.filter(function (entry) {
      return state.filter === 'all' || entry.type === state.filter;
    });

    releaseGrid.innerHTML = entries.map(releaseCard).join('');
    releaseGrid.hidden = entries.length === 0;
    if (releaseEmpty) releaseEmpty.hidden = entries.length !== 0;
  }

  function fallbackReleases() {
    var source = document.getElementById('release-fallback');
    if (!source) return [];
    try {
      var parsed = JSON.parse(source.textContent);
      return Array.isArray(parsed.items) ? parsed.items : [];
    } catch (error) {
      return [];
    }
  }

  function loadReleases() {
    var fallback = fallbackReleases();
    state.releases = fallback;
    renderReleases();

    if (window.location.protocol === 'file:') return Promise.resolve(fallback);

    return fetch('bioten-pha-waterborne-varnish/data/releases.json', { cache: 'no-store' })
      .then(function (response) {
        if (!response.ok) throw new Error('release-data-unavailable');
        return response.json();
      })
      .then(function (payload) {
        if (payload && Array.isArray(payload.items) && payload.items.length) {
          state.releases = payload.items;
          renderReleases();
        }
        return state.releases;
      })
      .catch(function () {
        return fallback;
      });
  }

  function setupReleaseFilters() {
    if (!releaseFilters) return;
    releaseFilters.addEventListener('click', function (event) {
      var button = event.target.closest('button[data-filter]');
      if (!button) return;

      state.filter = button.getAttribute('data-filter') || 'all';
      releaseFilters.querySelectorAll('button').forEach(function (item) {
        item.classList.toggle('is-active', item === button);
      });
      renderReleases();
    });
  }

  function setupReveal() {
    var items = Array.prototype.slice.call(document.querySelectorAll('[data-reveal]'));
    if (!items.length) return;

    if (!('IntersectionObserver' in window) || window.matchMedia('(prefers-reduced-motion: reduce)').matches) {
      items.forEach(function (item) { item.classList.add('is-visible'); });
      return;
    }

    var observer = new IntersectionObserver(function (entries) {
      entries.forEach(function (entry) {
        if (!entry.isIntersecting) return;
        entry.target.classList.add('is-visible');
        observer.unobserve(entry.target);
      });
    }, { threshold: 0.12, rootMargin: '0px 0px -6% 0px' });

    items.forEach(function (item) { observer.observe(item); });
  }

  function setupSectionNavigation() {
    var sections = Array.prototype.slice.call(document.querySelectorAll('[data-section]'));
    var links = Array.prototype.slice.call(document.querySelectorAll('[data-section-link]'));
    var manualNavigationUntil = 0;
    if (!sections.length || !links.length) return;

    function setActiveLink(id) {
      links.forEach(function (link) {
        link.classList.toggle('is-active', link.getAttribute('data-section-link') === id);
      });
    }

    links.forEach(function (link) {
      link.addEventListener('click', function () {
        manualNavigationUntil = Date.now() + 900;
        setActiveLink(link.getAttribute('data-section-link'));
      });
    });

    if (!('IntersectionObserver' in window)) return;

    var sectionObserver = new IntersectionObserver(function (entries) {
      if (Date.now() < manualNavigationUntil) return;
      var visible = entries
        .filter(function (entry) { return entry.isIntersecting; })
        .sort(function (a, b) { return b.intersectionRatio - a.intersectionRatio; })[0];

      if (!visible) return;
      var id = visible.target.getAttribute('data-section');
      setActiveLink(id);
    }, { threshold: [0.18, 0.35, 0.55], rootMargin: '-20% 0px -58% 0px' });

    sections.forEach(function (section) { sectionObserver.observe(section); });
  }

  if (languageToggle && !languageToggle.dataset.dbcNavigationLanguageBound) {
    languageToggle.addEventListener('click', function () {
      applyLanguage(state.language === 'zh' ? 'en' : 'zh');
    });
  }

  document.addEventListener('dbc:languagechange', function (event) {
    applyLanguage(event.detail && event.detail.language === 'en' ? 'en' : 'zh');
  });

  if (navToggle) navToggle.addEventListener('click', togglePrimaryNav);

  if (primaryNav) {
    primaryNav.addEventListener('click', function (event) {
      if (event.target.closest('a')) closePrimaryNav();
    });
  }

  window.addEventListener('resize', function () {
    if (window.innerWidth > 900) closePrimaryNav();
  });

  setupReleaseFilters();
  setupReveal();
  setupSectionNavigation();
  applyLanguage(readSavedLanguage());
  loadReleases();
})();