(function () {
  const qs = (sel, ctx = document) => ctx.querySelector(sel);
  const qsa = (sel, ctx = document) => Array.from(ctx.querySelectorAll(sel));

  // Mobile menu
  const menuToggle = qs('#menuToggle');
  const mobileMenu = qs('#mobileMenu');
  if (menuToggle && mobileMenu) {
    menuToggle.addEventListener('click', () => {
      const isHidden = mobileMenu.classList.contains('hidden');
      mobileMenu.classList.toggle('hidden', !isHidden);
      menuToggle.setAttribute('aria-expanded', String(isHidden));
    });
  }

  // Expand/Collapse all curriculum modules
  const expandBtn = qs('#expandAll');
  const modules = qsa('.module');
  if (expandBtn && modules.length) {
    const toggleAll = () => {
      const shouldOpen = expandBtn.dataset.state !== 'open';
      modules.forEach((mod) => {
        const content = qs('.module-content', mod);
        const icon = qs('.module-icon', mod);
        const summaryBtn = qs('.module-toggle', mod);
        if (shouldOpen) {
          openModule(mod, content, icon, summaryBtn, false);
        } else {
          closeModule(mod, content, icon, summaryBtn, false);
        }
      });
      expandBtn.dataset.state = shouldOpen ? 'open' : 'closed';
      const icon = qs('i', expandBtn);
      if (icon) {
        icon.setAttribute('data-feather', shouldOpen ? 'minus-square' : 'plus-square');
        // Replace icon
        if (window.feather && typeof feather.replace === 'function') {
          feather.replace();
        }
      }
    };
    expandBtn.addEventListener('click', toggleAll);
  }

  // Individual module toggle
  function openModule(module, content, icon, summaryBtn, animate = true) {
    summaryBtn.setAttribute('aria-expanded', 'true');
    content.classList.remove('hidden');
    content.classList.add('open');
    if (icon) icon.style.transform = 'rotate(180deg)';
    if (animate) {
      // auto height animation
      content.style.maxHeight = '0px';
      requestAnimationFrame(() => {
        content.style.maxHeight = content.scrollHeight + 'px';
      });
      const onEnd = (e) => {
        if (e.propertyName !== 'max-height') return;
        content.style.maxHeight = 'none';
        content.removeEventListener('transitionend', onEnd);
      };
      content.addEventListener('transitionend', onEnd);
    } else {
      content.style.maxHeight = 'none';
    }
  }

  function closeModule(module, content, icon, summaryBtn, animate = true) {
    summaryBtn.setAttribute('aria-expanded', 'false');
    if (animate) {
      // from current height to 0
      content.style.maxHeight = content.scrollHeight + 'px';
      requestAnimationFrame(() => {
        content.style.maxHeight = '0px';
      });
      const onEnd = (e) => {
        if (e.propertyName !== 'max-height') return;
        content.classList.remove('open');
        content.classList.add('hidden');
        content.style.maxHeight = '';
        content.removeEventListener('transitionend', onEnd);
      };
      content.addEventListener('transitionend', onEnd);
    } else {
      content.classList.remove('open');
      content.classList.add('hidden');
      content.style.maxHeight = '';
    }
    if (icon) icon.style.transform = 'rotate(0deg)';
  }

  modules.forEach((mod) => {
    const content = qs('.module-content', mod);
    const icon = qs('.module-icon', mod);
    const summaryBtn = qs('.module-toggle', mod);

    summaryBtn.addEventListener('click', (e) => {
      e.preventDefault();
      const isOpen = summaryBtn.getAttribute('aria-expanded') === 'true';
      if (isOpen) {
        closeModule(mod, content, icon, summaryBtn, true);
      } else {
        openModule(mod, content, icon, summaryBtn, true);
      }
    });
  });

  // FAQ accordion behavior: only one open at a time
  const faqs = qsa('#faq details');
  if (faqs.length) {
    faqs.forEach((faq) => {
      faq.addEventListener('toggle', () => {
        if (faq.open) {
          faqs.forEach((other) => {
            if (other !== faq) other.removeAttribute('open');
          });
        }
      });
    });
  }

  // Smooth scroll offset for fixed header
  const offset = 16; // header height-ish
  qsa('a[href^="#"]').forEach((a) => {
    a.addEventListener('click', (e) => {
      const id = a.getAttribute('href');
      if (!id || id === '#') return;
      const el = qs(id);
      if (!el) return;
      e.preventDefault();
      const top = el.getBoundingClientRect().top + window.scrollY - offset;
      window.scrollTo({ top, behavior: 'smooth' });
      history.pushState(null, '', id);
    });
  });

  // Footer year
  const yearEl = qs('#year');
  if (yearEl) {
    yearEl.textContent = String(new Date().getFullYear());
  }

  // Replace Feather icons if dynamically inserted
  if (window.feather && typeof feather.replace === 'function') {
    feather.replace();
  }
})();