let lastScrollTop = 0;
let header = null;

function handleScroll() {
  const scrollTop = window.pageYOffset || document.documentElement.scrollTop;
  
  if (!header) {
    header = document.getElementById('global-header');
    if (!header) return;
  }
  
  if (scrollTop > lastScrollTop && scrollTop > 100) {
    // Scrolling down & past 100px - hide header
    header.style.transform = 'translateY(-100%)';
    header.style.transition = 'transform 0.3s ease-in-out';
  } else {
    // Scrolling up or at top - show header
    header.style.transform = 'translateY(0)';
    header.style.transition = 'transform 0.3s ease-in-out';
  }
  
  lastScrollTop = scrollTop <= 0 ? 0 : scrollTop;
}

function init() {
  header = document.getElementById('global-header');
  window.addEventListener('scroll', handleScroll);
}

function teardown() {
  window.removeEventListener('scroll', handleScroll);
  if (header) {
    header.style.transform = '';
    header.style.transition = '';
  }
}

export { init, teardown };