document.addEventListener('DOMContentLoaded', () => {
    const header = document.getElementById('site-header');
    const backToTop = document.getElementById('backToTopBtn');
    const toggle = document.getElementById('mobile-menu-toggle');
    const mobileMenu = document.getElementById('mobile-menu');
    const revealItems = document.querySelectorAll('.reveal');

    const handleScroll = () => {
        const scrolled = window.scrollY > 24;
        if (header) {
            header.classList.toggle('is-scrolled', scrolled);
        }
        if (backToTop) {
            backToTop.classList.toggle('is-visible', window.scrollY > 380);
        }
    };

    handleScroll();
    window.addEventListener('scroll', handleScroll, { passive: true });

    if (backToTop) {
        backToTop.addEventListener('click', () => {
            window.scrollTo({ top: 0, behavior: 'smooth' });
        });
    }

    if (toggle && mobileMenu) {
        const openIcon = toggle.querySelector('.menu-open-icon');
        const closeIcon = toggle.querySelector('.menu-close-icon');

        toggle.addEventListener('click', () => {
            const nextState = !mobileMenu.classList.contains('is-open');
            mobileMenu.classList.toggle('is-open', nextState);
            toggle.setAttribute('aria-expanded', String(nextState));
            openIcon?.classList.toggle('hidden', nextState);
            closeIcon?.classList.toggle('hidden', !nextState);
        });

        mobileMenu.querySelectorAll('a').forEach((link) => {
            link.addEventListener('click', () => {
                mobileMenu.classList.remove('is-open');
                toggle.setAttribute('aria-expanded', 'false');
                openIcon?.classList.remove('hidden');
                closeIcon?.classList.add('hidden');
            });
        });
    }

    if ('IntersectionObserver' in window && revealItems.length) {
        const observer = new IntersectionObserver((entries) => {
            entries.forEach((entry) => {
                if (entry.isIntersecting) {
                    entry.target.classList.add('is-visible');
                    observer.unobserve(entry.target);
                }
            });
        }, { threshold: 0.15, rootMargin: '0px 0px -40px 0px' });

        revealItems.forEach((item) => observer.observe(item));
    } else {
        revealItems.forEach((item) => item.classList.add('is-visible'));
    }
});