(() => {
  'use strict';

  const nav = document.getElementById('nav');
  const burger = document.getElementById('burger');
  const navLinks = document.querySelector('.nav__links');
  const yearEl = document.getElementById('year');
  const parallaxEls = Array.from(document.querySelectorAll('[data-parallax]'));
  const revealEls = Array.from(document.querySelectorAll('.reveal'));

  if (yearEl) yearEl.textContent = new Date().getFullYear();

  /* ---- Sticky / scrolled nav ---- */
  const onScroll = () => {
    if (window.scrollY > 30) nav.classList.add('is-scrolled');
    else nav.classList.remove('is-scrolled');
    updateParallax();
  };

  /* ---- Mobile menu toggle ---- */
  if (burger && navLinks) {
    burger.addEventListener('click', () => {
      const open = navLinks.classList.toggle('is-open');
      burger.classList.toggle('is-open', open);
      burger.setAttribute('aria-expanded', String(open));
    });
    navLinks.querySelectorAll('a').forEach((a) =>
      a.addEventListener('click', () => {
        navLinks.classList.remove('is-open');
        burger.classList.remove('is-open');
        burger.setAttribute('aria-expanded', 'false');
      })
    );
  }

  /* ---- Parallax (rAF-throttled) ---- */
  let ticking = false;
  const reduced = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  function updateParallax() {
    if (reduced) return;
    if (ticking) return;
    ticking = true;
    requestAnimationFrame(() => {
      const vh = window.innerHeight;
      const vw = window.innerWidth;
      parallaxEls.forEach((el) => {
        const rect = el.getBoundingClientRect();
        // Only process elements roughly in / near the viewport
        if (rect.bottom < -vh || rect.top > vh * 2) return;
        const speed = parseFloat(el.dataset.parallax) || 0.2;
        // Distance of element center from viewport center
        const center = rect.top + rect.height / 2 - vh / 2;
        const offset = -center * speed;
        // Use translate3d for GPU acceleration
        el.style.transform = `translate3d(0, ${offset.toFixed(1)}px, 0)`;
      });
      ticking = false;
    });
  }

  /* ---- Scroll reveal via IntersectionObserver ---- */
  if ('IntersectionObserver' in window) {
    const io = new IntersectionObserver(
      (entries) => {
        entries.forEach((entry) => {
          if (entry.isIntersecting) {
            entry.target.classList.add('is-visible');
            io.unobserve(entry.target);
          }
        });
      },
      { threshold: 0.15, rootMargin: '0px 0px -60px 0px' }
    );
    revealEls.forEach((el) => io.observe(el));
  } else {
    revealEls.forEach((el) => el.classList.add('is-visible'));
  }

  /* ---- Smooth-scroll offset for fixed nav ---- */
  document.querySelectorAll('a[href^="#"]').forEach((a) => {
    a.addEventListener('click', (e) => {
      const id = a.getAttribute('href');
      if (id.length < 2) return;
      const target = document.querySelector(id);
      if (!target) return;
      e.preventDefault();
      const navH = nav.offsetHeight;
      const top = target.getBoundingClientRect().top + window.scrollY - navH + 4;
      window.scrollTo({ top, behavior: 'smooth' });
    });
  });

  /* ---- Listeners ---- */
  window.addEventListener('scroll', onScroll, { passive: true });
  window.addEventListener('resize', updateParallax);
  // initial paint
  onScroll();
  updateParallax();
})();