function loadHTML(file, elementId, callback) {
  fetch(file)
    .then(r => r.text())
    .then(html => {
      document.getElementById(elementId).innerHTML = html;
      if (callback) callback();
    })
    .catch(err => console.error('Error loading:', file, err));
}

function highlightActiveNav() {
  const current = location.pathname.split('/').pop() || 'index.html';
  document.querySelectorAll('#header a[href]').forEach(link => {
    if (link.getAttribute('href') === `/${current}`) {
      link.classList.add('active');
    }
  });
}

function startCarousel() {
  const slides = document.querySelectorAll('#hero-carousel .carousel-slide');
  if (!slides.length) return;
  let current = 0;
  slides[current].style.opacity = '1';
  setInterval(() => {
    slides[current].style.opacity = '0';
    current = (current + 1) % slides.length;
    slides[current].style.opacity = '1';
  }, 5000);
}

loadHTML('/header.html', 'header', () => {
  highlightActiveNav();
  startCarousel();
});
loadHTML('/footer.html', 'footer');