(() => {
  'use strict';

  const root = document.documentElement;
  if (!root.matches('[data-v770-release="fullsite-logic-visual-quality-v7.7.0"]')) return;

  const currentFile = decodeURIComponent(location.pathname.split('/').pop() || 'index.html').toLowerCase();
  const primaryTitles = Object.freeze({
    'index.html': {
      zh: 'DBC 世界杯竞猜官网｜新材料应用创新平台 · BIOTEN 博碳生物',
      en: 'DBC | Advanced-Material Application Platform · BIOTEN'
    },
    'about.html': {
      zh: '关于世界杯竞猜官网｜新材料创新与产业应用平台',
      en: 'About DBC | New Material Innovation & Industrial Application Platform'
    },
    'bioten-platform.html': {
      zh: 'BIOTEN 博碳生物｜PHA 生物基水性功能乳液平台',
      en: 'BIOTEN | PHA Bio-Based Waterborne Functional Emulsion Platform'
    },
    'bioten.html': {
      zh: 'BIOTEN 博碳包装｜纸基包装阻隔系统工程',
      en: 'BIOTEN Packaging | Barrier Systems Engineering for Fiber-Based Packaging'
    },
    'bioten-lab.html': {
      zh: 'BIOTEN 开发者｜问题定义、联合开发与证据协同',
      en: 'BIOTEN Developer | Problem Definition, Joint Development and Evidence Coordination'
    },
    'news.html': {
      zh: '新闻与洞察｜材料科技进展与产业实践｜DBC 世界杯竞猜官网',
      en: 'News & Insights | Materials Progress and Industry Practice | DBC'
    },
    'patent-evidence.html': {
      zh: '研发与专利技术资产｜材料与产品创新｜DBC · BIOTEN',
      en: 'R&D and Patent Technology Assets | Material & Product Innovation | DBC · BIOTEN'
    }
  });

  function pageLanguage() {
    return root.dataset.lang === 'en' || root.lang.toLowerCase().startsWith('en') ? 'en' : 'zh';
  }

  function setLocalizedText(element, value) {
    if (!element.children.length) {
      if (element.textContent !== value) element.textContent = value;
      return;
    }

    const directText = [...element.childNodes].find((node) => node.nodeType === Node.TEXT_NODE && node.nodeValue.trim());
    if (directText && directText.nodeValue.trim() !== value) directText.nodeValue = `${value} `;
  }

  function stabilizeBilingualState() {
    if (!document.body?.matches('[data-en-ready="true"], [data-en-ready=""]')) return;
    const language = pageLanguage();
    const key = language === 'en' ? 'navEn' : 'navCn';

    document.querySelectorAll('[data-nav-cn][data-nav-en]').forEach((element) => {
      const value = element.dataset[key];
      if (typeof value === 'string') setLocalizedText(element, value);
    });

    document.querySelectorAll('[data-aria-cn][data-aria-en]').forEach((element) => {
      const value = element.dataset[language === 'en' ? 'ariaEn' : 'ariaCn'];
      if (typeof value === 'string') element.setAttribute('aria-label', value);
    });

    document.querySelectorAll('[data-alt-cn][data-alt-en]').forEach((element) => {
      const value = element.dataset[language === 'en' ? 'altEn' : 'altCn'];
      if (typeof value === 'string') element.setAttribute('alt', value);
    });

    const title = primaryTitles[currentFile]?.[language];
    if (title && document.title !== title) document.title = title;

    document.querySelectorAll('footer.site-footer .footer-directory').forEach((navigation) => {
      navigation.setAttribute('aria-label', language === 'en' ? 'Website footer navigation' : '网站页脚导航');
    });

    document.querySelectorAll('[data-v7111-footer-toggle]').forEach((button) => {
      const heading = button.dataset[key] || button.textContent.trim();
      button.setAttribute('aria-label', language === 'en' ? `${heading} footer directory` : `${heading}页脚目录`);
    });
  }

  function scheduleBilingualStabilization() {
    stabilizeBilingualState();
    requestAnimationFrame(stabilizeBilingualState);
    [90, 320, 900].forEach((delay) => window.setTimeout(stabilizeBilingualState, delay));
  }

  function safeId(text, index) {
    const normalized = String(text || '')
      .trim()
      .toLowerCase()
      .replace(/[^a-z0-9\u3400-\u9fff]+/g, '-')
      .replace(/^-+|-+$/g, '')
      .slice(0, 42);
    return `article-section-${normalized || index + 1}`;
  }

  function enhanceArticleReading() {
    const body = document.body;
    if (!body.matches('.v750-site[data-v750-page="article"]')) return;

    const article = document.querySelector('.news-article, .news-original-article');
    const chineseBody = document.querySelector('.news-body[data-v750-original-cn]');
    const content = chineseBody?.querySelector('.news-content');
    if (!article || !chineseBody || !content) return;

    const headings = [...content.querySelectorAll(':scope > h2')];
    headings.forEach((heading, index) => {
      if (!heading.id) heading.id = safeId(heading.textContent, index);
    });

    if (headings.length > 1) {
      const details = document.createElement('details');
      details.className = 'v770-article-toc';
      const summary = document.createElement('summary');
      summary.textContent = root.dataset.lang === 'en' ? 'Article outline' : '文章目录';
      const list = document.createElement('ol');

      headings.forEach((heading) => {
        const item = document.createElement('li');
        const link = document.createElement('a');
        link.href = `#${heading.id}`;
        link.textContent = heading.textContent.trim();
        item.append(link);
        list.append(item);
      });

      details.append(summary, list);
      chineseBody.parentNode.insertBefore(details, chineseBody);
    }

    const progress = document.createElement('div');
    progress.className = 'v770-reading-progress';
    progress.setAttribute('aria-hidden', 'true');
    const bar = document.createElement('span');
    progress.append(bar);
    document.body.append(progress);

    let ticking = false;
    const update = () => {
      const rect = article.getBoundingClientRect();
      const articleTop = window.scrollY + rect.top;
      const distance = Math.max(1, article.scrollHeight - window.innerHeight);
      const ratio = Math.min(1, Math.max(0, (window.scrollY - articleTop) / distance));
      bar.style.width = `${ratio * 100}%`;
      ticking = false;
    };

    const requestUpdate = () => {
      if (ticking) return;
      ticking = true;
      requestAnimationFrame(update);
    };

    addEventListener('scroll', requestUpdate, { passive: true });
    addEventListener('resize', requestUpdate, { passive: true });
    update();
  }

  function markScrollableRegions() {
    const candidates = document.querySelectorAll([
      '.v281-path ol',
      '.dv2-local-nav__inner',
      '.dev740-engine__rail',
      '.dv21-domain-stages',
      '.v750-index-controls',
      '.resources-page-nav'
    ].join(','));

    const inspect = () => {
      candidates.forEach((element) => {
        const scrollable = element.scrollWidth > element.clientWidth + 4;
        element.toggleAttribute('data-v770-scrollable', scrollable);
        if (scrollable && !element.hasAttribute('tabindex')) element.tabIndex = 0;
      });
    };

    inspect();
    addEventListener('resize', inspect, { passive: true });
  }

  function addLanguageBoundary() {
    const chineseOnlyForms = new Set([
      'contact-intent-paper-sample.html',
      'sample.html',
      'sample_antux.html',
      'sample_casu.html',
      'sample_dpu.html'
    ]);
    if (!chineseOnlyForms.has(currentFile)) return;

    const main = document.querySelector('main');
    if (!main || main.querySelector('.v770-language-boundary')) return;

    const note = document.createElement('p');
    note.className = 'v770-language-boundary';
    note.setAttribute('role', 'note');
    note.textContent = '项目申请流程当前以中文收集；英文项目可通过 Contact 页面联系专业团队。 · This intake form currently collects project information in Chinese; English enquiries can be routed through Contact.';
    main.prepend(note);
  }

  function normalizeExternalLinks() {
    document.querySelectorAll('a[href^="http"]').forEach((link) => {
      try {
        const target = new URL(link.href, location.href);
        if (target.origin !== location.origin) {
          const rel = new Set((link.getAttribute('rel') || '').split(/\s+/).filter(Boolean));
          rel.add('noopener');
          rel.add('noreferrer');
          link.setAttribute('rel', [...rel].join(' '));
        }
      } catch (_) {
        // Invalid external links are reported by static QA; do not mutate them here.
      }
    });
  }

  function init() {
    document.body.classList.add('v770-quality-ready');
    enhanceArticleReading();
    markScrollableRegions();
    addLanguageBoundary();
    normalizeExternalLinks();
    scheduleBilingualStabilization();
  }

  document.addEventListener('dbc:languagechange', scheduleBilingualStabilization);
  document.addEventListener('dbc:translations-loaded', scheduleBilingualStabilization);

  const languageObserver = new MutationObserver((mutations) => {
    if (mutations.some((mutation) => mutation.attributeName === 'lang' || mutation.attributeName === 'data-lang')) {
      scheduleBilingualStabilization();
    }
  });
  languageObserver.observe(root, { attributes: true, attributeFilter: ['lang', 'data-lang'] });

  if (document.readyState === 'loading') {
    document.addEventListener('DOMContentLoaded', init, { once: true });
  } else {
    init();
  }
})();