const DEFAULT_VISIBLE_PROJECTS = 9;

initProjectFilters();
initMobileNav();
initActiveNavLink();
initRevealOnScroll();

function initRevealOnScroll() {
  const revealTargets = document.querySelectorAll('.reveal');
  if (
    revealTargets.length === 0 ||
    !('IntersectionObserver' in window) ||
    window.matchMedia('(prefers-reduced-motion: reduce)').matches
  ) {
    return;
  }

  const observer = new IntersectionObserver(
    (entries, currentObserver) => {
      entries.forEach((entry) => {
        if (!entry.isIntersecting) {
          return;
        }

        entry.target.classList.add('visible');
        currentObserver.unobserve(entry.target);
      });
    },
    { threshold: 0.1, rootMargin: '0px 0px -40px 0px' }
  );

  revealTargets.forEach((target) => {
    observer.observe(target);
    target.classList.add('reveal-pending');
  });
}

function initActiveNavLink() {
  const sections = Array.from(document.querySelectorAll('section[id]'));
  const navLinks = Array.from(
    document.querySelectorAll('.nav-links a, .mobile-nav-links a')
  );
  if (
    sections.length === 0 ||
    navLinks.length === 0 ||
    !('IntersectionObserver' in window)
  ) {
    return;
  }

  const visibleSections = new Set();
  const updateActiveNavLink = (entries) => {
    entries.forEach((entry) => {
      if (entry.isIntersecting) {
        visibleSections.add(entry.target);
      } else {
        visibleSections.delete(entry.target);
      }
    });
    const currentSection = sections
      .filter((section) => visibleSections.has(section))
      .at(-1);
    if (!currentSection) {
      return;
    }
    navLinks.forEach((link) => {
      const isActive = link.getAttribute('href') === `#${currentSection.id}`;
      link.classList.toggle('is-active', isActive);
      if (isActive) {
        link.setAttribute('aria-current', 'location');
      } else {
        link.removeAttribute('aria-current');
      }
    });
  };
  let observer;
  const observeSections = () => {
    observer?.disconnect();
    visibleSections.clear();
    observer = new IntersectionObserver(updateActiveNavLink, {
      rootMargin: `-56px 0px -${Math.max(0, window.innerHeight - 160)}px 0px`,
    });
    sections.forEach((section) => observer.observe(section));
  };
  observeSections();
  window.addEventListener('resize', observeSections);
}

function initMobileNav() {
  const menu = document.querySelector('.nav-menu');
  if (!menu) {
    return;
  }
  menu.querySelectorAll('a').forEach((link) => {
    link.addEventListener('click', () => {
      menu.open = false;
    });
  });
  menu.addEventListener('keydown', (event) => {
    if (event.key === 'Escape' && menu.open) {
      menu.open = false;
      menu.querySelector('summary').focus();
    }
  });
}

function initProjectFilters() {
  const filterChips = Array.from(document.querySelectorAll('.filter-chip'));
  const projectCards = Array.from(
    document.querySelectorAll('#project-grid .project-card')
  );
  if (filterChips.length === 0 || projectCards.length === 0) {
    return;
  }

  const seeMoreButton = document.querySelector('#projects-see-more');
  const projectCount = document.querySelector('#project-count');
  const emptyState = document.querySelector('#projects-empty');
  const projectGrid = document.querySelector('#project-grid');
  const filters = document.querySelector('.project-filters');
  const resetButton = document.querySelector('#projects-reset');
  const techByCard = new Map(
    projectCards.map((card) => [
      card,
      (card.dataset.tech || '').split(/\s+/).filter(Boolean),
    ])
  );

  let selectedFilter = 'all';
  let isExpanded = false;

  const applyFilter = () => {
    const matchingCards = projectCards.filter(
      (card) =>
        selectedFilter === 'all' ||
        techByCard.get(card).includes(selectedFilter)
    );
    const shownCards = isExpanded
      ? matchingCards
      : matchingCards.slice(0, DEFAULT_VISIBLE_PROJECTS);
    const shownSet = new Set(shownCards);
    projectCards.forEach((card) => {
      card.hidden = !shownSet.has(card);
    });

    filterChips.forEach((chip) => {
      const isSelected = chip.dataset.filter === selectedFilter;
      chip.classList.toggle('active', isSelected);
      chip.setAttribute('aria-pressed', String(isSelected));
    });
    if (projectCount) {
      const label = filterChips
        .find((chip) => chip.dataset.filter === selectedFilter)
        .textContent.trim();
      projectCount.hidden = false;
      projectCount.textContent =
        `Showing ${shownCards.length} of ${matchingCards.length} project${matchingCards.length === 1 ? '' : 's'}` +
        (selectedFilter === 'all' ? '' : ` (${label})`);
    }
    if (emptyState) {
      emptyState.hidden = matchingCards.length !== 0;
    }
    if (projectGrid) {
      projectGrid.hidden = matchingCards.length === 0;
    }
    if (seeMoreButton) {
      const remainingCount = matchingCards.length - shownCards.length;
      seeMoreButton.hidden = matchingCards.length <= DEFAULT_VISIBLE_PROJECTS;
      seeMoreButton.setAttribute('aria-expanded', String(isExpanded));
      seeMoreButton.textContent = isExpanded
        ? 'Show fewer projects'
        : `Show ${remainingCount} more project${remainingCount === 1 ? '' : 's'}`;
    }
  };

  filterChips.forEach((chip) => {
    chip.addEventListener('click', () => {
      selectedFilter = chip.dataset.filter || 'all';
      isExpanded = false;

      applyFilter();
    });
  });

  if (seeMoreButton) {
    seeMoreButton.addEventListener('click', () => {
      isExpanded = !isExpanded;
      applyFilter();
      if (!isExpanded) {
        seeMoreButton.scrollIntoView({ block: 'nearest', behavior: 'instant' });
      }
    });
  }

  if (resetButton) {
    resetButton.addEventListener('click', () => {
      selectedFilter = 'all';
      isExpanded = false;
      applyFilter();
      filterChips.find((chip) => chip.dataset.filter === 'all').focus();
    });
  }

  applyFilter();
  if (filters) {
    filters.hidden = false;
  }
}