'use client';
import { useEffect } from 'react';
import { usePathname } from 'next/navigation';
const targets = '.reference-service-card, .reference-about-intro, .reference-about-values, .reference-faq, .reference-contact > div, .section-heading, .service-row, .service-detail, .about-band-grid, .contact-cta, .about-intro, .values-grid > div, .faq-section, .contact-info > div, .offices-grid > article, .contact-form, .portfolio-grid > article, .portfolio-detail';
export default function PageMotion() {
  const pathname = usePathname();
  useEffect(() => {
    const main = document.getElementById('main');
    if (!main || !('IntersectionObserver' in window)) return;
    const preference = window.matchMedia('(prefers-reduced-motion: reduce)');
    const seen = new WeakSet();
    const prepared = new Set();
    const observer = new IntersectionObserver(entries => {
      for (const entry of entries) {
        if (!entry.isIntersecting) continue;
        observer.unobserve(entry.target);
        entry.target.dataset.scrollReveal = 'visible';
      }
    }, { threshold: 0, rootMargin: '0px 0px 48px 0px' });
    const prepare = element => {
      if (seen.has(element)) return;
      seen.add(element);
      // Never hide already-visible content, restored scroll positions, or filtered cards.
      if (preference.matches || element.getBoundingClientRect().top < window.innerHeight) return;
      element.dataset.scrollReveal = 'pending';
      prepared.add(element);
      observer.observe(element);
    };
    main.querySelectorAll(targets).forEach(prepare);
    // Inspect added subtrees only; do not rescan the page on every Swiper update.
    const mutations = new MutationObserver(records => {
      for (const record of records) {
        for (const node of record.addedNodes) {
          if (!(node instanceof Element)) continue;
          if (node.matches(targets)) prepare(node);
          node.querySelectorAll(targets).forEach(prepare);
        }
      }
      for (const element of prepared) {
        if (!element.isConnected) {
          observer.unobserve(element);
          prepared.delete(element);
        }
      }
    });
    mutations.observe(main, { childList: true, subtree: true });
    const revealAll = () => {
      observer.disconnect();
      prepared.forEach(element => element.removeAttribute('data-scroll-reveal'));
      prepared.clear();
    };
    const onPreferenceChange = () => { if (preference.matches) revealAll(); };
    preference.addEventListener('change', onPreferenceChange);
    return () => {
      mutations.disconnect();
      revealAll();
      preference.removeEventListener('change', onPreferenceChange);
    };
  }, [pathname]);
  return null;
}