// ---------- SHARED UTILITIES ----------
function readCssPx(name, fallback, el = document.documentElement){
  const value = getComputedStyle(el).getPropertyValue(name).trim();
  const parsed = parseFloat(value);
  return Number.isFinite(parsed) ? parsed : fallback;
}

const prefersReducedMotion = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

// ---------- ЯЗЫК (переключатель = ссылки на статические URL) ----------
function initLangSwitch(){
  const root = document.getElementById('langSwitch');
  if (!root) return;

  root.querySelectorAll('a[data-set-lang]').forEach(link => {
    link.addEventListener('click', () => {
      const lang = link.getAttribute('data-set-lang');
      if (lang === 'ru' || lang === 'en' || lang === 'ua') {
        localStorage.setItem('lang', lang);
      }
    });
  });
}

// ---------- ТЕМА ----------
function getSystemTheme(){
  return window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
}

function resolveTheme(){
  const saved = localStorage.getItem('theme');
  if (saved === 'light' || saved === 'dark') return saved;
  return getSystemTheme();
}

function applyTheme(theme){
  document.documentElement.setAttribute('data-theme', theme);
}

function initTheme(){
  const themeToggle = document.getElementById('themeToggle');
  const media = window.matchMedia('(prefers-color-scheme: dark)');

  applyTheme(resolveTheme());

  themeToggle.addEventListener('click', () => {
    const current = document.documentElement.getAttribute('data-theme');
    const next = current === 'light' ? 'dark' : 'light';
    applyTheme(next);
    localStorage.setItem('theme', next);
  });

  const onSystemChange = () => {
    if (localStorage.getItem('theme')) return;
    applyTheme(getSystemTheme());
  };
  if (typeof media.addEventListener === 'function') {
    media.addEventListener('change', onSystemChange);
  } else if (typeof media.addListener === 'function') {
    media.addListener(onSystemChange);
  }
}

// ---------- HERO LOGO SCROLL ANIMATION ----------
function initHeroScroll(config){
  const {
    section,
    stage,
    brand,
    brandInner,
    mobileAnimClass,
    scrollDrivenClass,
    brandScaleAnimation,
    syncFit,
    brandGapFromSection = false,
    clampMobileScale = null,
    clearSectionVars = null,
    setMobileScaleVar = false,
    subtractRunwayOnMobile = true
  } = config;

  const siteHeader = document.querySelector('.site-header');
  const mainNav = document.querySelector('.main-nav');

  let cachedBaseHeight = 0;
  let cachedBrandGap = 32;
  let cachedMaxScale = 1.9;
  let cachedMaxBrandHeight = 0;
  let cachedMinBrandHeight = 0;
  let cachedNavHeight = 0;
  let heroRunway = 0;
  let heroStartY = 0;
  let heroResizeTimer = 0;
  let heroIsMobile = false;
  let heroUseScrollTimeline = false;
  let lastHeroScrollStep = -1;
  let postHeroLift = null;

  const heroRoot = document.documentElement;

  function clearHeroAnimationVars(){
    heroRoot.style.removeProperty('--hero-scale');
    heroRoot.style.removeProperty('--hero-brand-height');
    heroRoot.style.removeProperty('--hero-stage-height');
    heroRoot.style.removeProperty('--hero-brand-max-h');
    heroRoot.style.removeProperty('--hero-brand-min-h');
    heroRoot.style.removeProperty('--hero-nav-shift');
    heroRoot.style.removeProperty('--hero-nav-shift-max');
    heroRoot.style.removeProperty('--hero-scroll-start');
    heroRoot.style.removeProperty('--hero-scroll-end');
    if (brandInner){
      brandInner.style.removeProperty('animation-range');
      brandInner.style.removeProperty('animation-timeline');
      brandInner.style.removeProperty('animation');
    }
    if (mainNav){
      mainNav.style.removeProperty('animation-range');
      mainNav.style.removeProperty('animation-timeline');
      mainNav.style.removeProperty('animation');
      mainNav.style.removeProperty('transform');
    }
    if (postHeroLift){
      postHeroLift.style.removeProperty('animation-range');
      postHeroLift.style.removeProperty('animation-timeline');
      postHeroLift.style.removeProperty('animation');
      postHeroLift.style.removeProperty('transform');
      delete postHeroLift.dataset.heroLiftExited;
    }
    if (clearSectionVars) clearSectionVars(section);
  }

  function ensurePostHeroLift(){
    if (postHeroLift?.isConnected) return postHeroLift;
    postHeroLift = section?.parentElement?.querySelector(':scope > .post-hero-lift') || null;
    return postHeroLift;
  }

  function applyHeroScrollAnimations(range){
    brandInner.style.animation = `${brandScaleAnimation} ease-out both`;
    brandInner.style.animationTimeline = 'scroll(root block)';
    brandInner.style.animationRange = range;
    mainNav.style.animation = 'hero-nav-lift ease-out both';
    mainNav.style.animationTimeline = 'scroll(root block)';
    mainNav.style.animationRange = range;
    ensurePostHeroLift();
    if (postHeroLift){
      postHeroLift.style.animation = 'hero-content-lift ease-out both';
      postHeroLift.style.animationTimeline = 'scroll(root block)';
      postHeroLift.style.animationRange = range;
      postHeroLift.style.removeProperty('transform');
      delete postHeroLift.dataset.heroLiftExited;
    }
  }

  function setHeroMobileMode(enabled){
    if (!section) return;
    section.classList.toggle(mobileAnimClass, enabled);
    section.classList.toggle(scrollDrivenClass, enabled && heroUseScrollTimeline);
    if (enabled) ensurePostHeroLift();
  }

  function getHeroScrollRunwayMultiplier(){
    return readCssPx('--hero-scroll-runway-multiplier', 1);
  }

  function getHeroEffectiveRunway(){
    return heroRunway * getHeroScrollRunwayMultiplier();
  }

  function getHeroAnimationRange(){
    return `${heroStartY}px ${heroStartY + getHeroEffectiveRunway()}px`;
  }

  function easeOutCubic(t){
    return 1 - (1 - t) ** 3;
  }

  function getHeroScrollProgress(){
    return Math.min(Math.max(window.scrollY - heroStartY, 0), getHeroEffectiveRunway());
  }

  function updateHeroContentLift(){
    if (!heroIsMobile || prefersReducedMotion || !section){
      if (postHeroLift) postHeroLift.style.removeProperty('transform');
      return;
    }

    ensurePostHeroLift();
    if (!postHeroLift) return;

    if (heroUseScrollTimeline){
      const exited = section.getBoundingClientRect().bottom <= 0;
      if (exited){
        if (postHeroLift.dataset.heroLiftExited !== '1'){
          postHeroLift.style.animation = 'none';
          postHeroLift.style.transform = 'translate3d(0, 0, 0)';
          postHeroLift.dataset.heroLiftExited = '1';
        }
        return;
      }
      if (postHeroLift.dataset.heroLiftExited === '1'){
        delete postHeroLift.dataset.heroLiftExited;
        const range = getHeroAnimationRange();
        postHeroLift.style.animation = 'hero-content-lift ease-out both';
        postHeroLift.style.animationTimeline = 'scroll(root block)';
        postHeroLift.style.animationRange = range;
        postHeroLift.style.removeProperty('transform');
      }
      return;
    }

    if (section.getBoundingClientRect().bottom <= 0){
      postHeroLift.style.transform = 'translate3d(0, 0, 0)';
      return;
    }
    const navShift = getComputedStyle(heroRoot).getPropertyValue('--hero-nav-shift').trim() || '0px';
    postHeroLift.style.transform = `translate3d(0, ${navShift}, 0)`;
  }

  function isHeroMobileViewport(){
    return window.innerWidth < 600;
  }

  function getHeroMaxScale(){
    const mobile = window.innerWidth < 600;
    const scope = section || document.documentElement;
    return readCssPx(mobile ? '--hero-max-scale-mobile' : '--hero-max-scale', mobile ? 1.6 : 2.2, scope);
  }

  function syncSiteHeaderHeight(){
    if (!siteHeader) return;
    const height = siteHeader.getBoundingClientRect().height;
    document.documentElement.style.setProperty('--site-header-height', `${Math.ceil(height)}px`);
  }

  function getHeroBrandHeight(scale){
    return cachedBaseHeight * scale + cachedBrandGap;
  }

  function getHeroStickyTop(){
    return readCssPx('--site-header-height', 57) + readCssPx('--hero-stage-offset', 80);
  }

  function measureHero(){
    syncSiteHeaderHeight();
    heroIsMobile = isHeroMobileViewport();
    lastHeroScrollStep = -1;

    if (!brandInner || !brand || !section || !stage || prefersReducedMotion){
      heroUseScrollTimeline = false;
      setHeroMobileMode(false);
      clearHeroAnimationVars();
      syncFit();
      return;
    }

    const gapScope = brandGapFromSection ? section : document.documentElement;
    cachedBrandGap = readCssPx('--hero-brand-gap', 32, gapScope);
    cachedMaxScale = getHeroMaxScale();
    clearHeroAnimationVars();
    brandInner.style.removeProperty('transform');

    syncFit();
    cachedBaseHeight = brandInner.offsetHeight;
    if (heroIsMobile){
      if (clampMobileScale){
        cachedMaxScale = clampMobileScale(cachedMaxScale, brand, brandInner, section);
      }
      cachedMaxBrandHeight = getHeroBrandHeight(cachedMaxScale);
      cachedMinBrandHeight = getHeroBrandHeight(1);
    } else {
      cachedMaxBrandHeight = getHeroBrandHeight(1);
      cachedMinBrandHeight = getHeroBrandHeight(1 / cachedMaxScale);
    }
    cachedNavHeight = mainNav ? mainNav.offsetHeight : 0;
    heroRunway = Math.max(cachedMaxBrandHeight - cachedMinBrandHeight, 0);
    heroStartY = stage.getBoundingClientRect().top + window.scrollY - getHeroStickyTop();

    heroUseScrollTimeline = heroIsMobile
      && typeof CSS !== 'undefined'
      && CSS.supports('animation-timeline', 'scroll()');

    if (heroIsMobile){
      setHeroMobileMode(true);
      if (setMobileScaleVar){
        section.style.setProperty('--hero-max-scale-mobile', cachedMaxScale.toFixed(4));
      }
      heroRoot.style.setProperty('--hero-brand-max-h', `${cachedMaxBrandHeight}px`);
      heroRoot.style.setProperty('--hero-brand-min-h', `${cachedMinBrandHeight}px`);
      heroRoot.style.setProperty('--hero-brand-height', `${cachedMaxBrandHeight}px`);
      heroRoot.style.setProperty('--hero-stage-height', `${cachedMaxBrandHeight + cachedNavHeight}px`);
      heroRoot.style.setProperty('--hero-nav-shift-max', `${-(cachedMaxBrandHeight - cachedMinBrandHeight)}px`);
      if (heroUseScrollTimeline){
        applyHeroScrollAnimations(getHeroAnimationRange());
      }
    } else {
      setHeroMobileMode(false);
    }

    updateHeroBrand();
    updateHeroContentLift();
  }

  function updateHeroBrand(){
    if (!brandInner || !brand || !stage || prefersReducedMotion || cachedBaseHeight <= 0) return;
    if (heroUseScrollTimeline) return;

    const scrolled = getHeroScrollProgress();
    const effectiveRunway = getHeroEffectiveRunway();
    const linearProgress = effectiveRunway > 0 ? scrolled / effectiveRunway : 1;
    const progress = easeOutCubic(Math.min(linearProgress, 1));

    if (heroIsMobile){
      const scale = cachedMaxScale - progress * (cachedMaxScale - 1);
      const brandHeight = cachedBaseHeight * scale + cachedBrandGap;
      const navShift = cachedMaxBrandHeight - brandHeight;

      heroRoot.style.setProperty('--hero-scale', scale.toFixed(4));
      heroRoot.style.setProperty('--hero-nav-shift', `${-navShift}px`);
      updateHeroContentLift();
      return;
    }

    if (scrolled === lastHeroScrollStep) return;
    lastHeroScrollStep = scrolled;

    const brandHeight = cachedMaxBrandHeight - progress * (cachedMaxBrandHeight - cachedMinBrandHeight);
    const scale = (brandHeight - cachedBrandGap) / cachedBaseHeight;

    heroRoot.style.setProperty('--hero-scale', scale.toFixed(4));
    heroRoot.style.setProperty('--hero-brand-height', `${brandHeight}px`);
    heroRoot.style.setProperty('--hero-stage-height', `${brandHeight + cachedNavHeight}px`);
  }

  let heroScrollRaf = 0;
  let heroLastScrollY = -1;

  function runHeroScrollFrame(){
    heroScrollRaf = 0;
    const scrollY = window.scrollY;

    if (heroIsMobile) updateHeroContentLift();
    if (!heroUseScrollTimeline) updateHeroBrand();

    if (scrollY !== heroLastScrollY){
      heroLastScrollY = scrollY;
      scheduleHeroScrollFrame();
    }
  }

  function scheduleHeroScrollFrame(){
    if (heroScrollRaf) return;
    heroScrollRaf = requestAnimationFrame(runHeroScrollFrame);
  }

  function onHeroScroll(){
    scheduleHeroScrollFrame();
  }

  function initHeroAnimation(){
    measureHero();
  }

  function scheduleHeroMeasure(){
    clearTimeout(heroResizeTimer);
    heroResizeTimer = setTimeout(initHeroAnimation, 120);
  }

  function getNavScrollOffset(){
    return readCssPx('--site-header-height', 57) + 24;
  }

  function getSectionScrollInset(target){
    const paddingTop = parseFloat(getComputedStyle(target).paddingTop);
    return Number.isFinite(paddingTop) ? paddingTop : 0;
  }

  function scrollToSection(target){
    const offset = getNavScrollOffset();
    let top = target.getBoundingClientRect().top + window.scrollY - offset + getSectionScrollInset(target);
    const belowHero = section
      && (section.compareDocumentPosition(target) & Node.DOCUMENT_POSITION_FOLLOWING);
    const canSubtractRunway = subtractRunwayOnMobile || !heroIsMobile;
    if (belowHero && heroRunway > 0 && canSubtractRunway && window.scrollY < heroStartY + heroRunway){
      top -= heroRunway;
    }

    window.scrollTo({
      top: Math.max(top, 0),
      behavior: prefersReducedMotion ? 'auto' : 'smooth'
    });
  }

  window.addEventListener('scroll', onHeroScroll, { passive: true });
  window.addEventListener('resize', scheduleHeroMeasure);
  window.addEventListener('load', initHeroAnimation);

  if (brandInner && window.ResizeObserver){
    const heroResizeObserver = new ResizeObserver(scheduleHeroMeasure);
    heroResizeObserver.observe(brandInner);
  }

  if (siteHeader && window.ResizeObserver){
    const headerResizeObserver = new ResizeObserver(scheduleHeroMeasure);
    headerResizeObserver.observe(siteHeader);
  }

  initHeroAnimation();

  document.querySelectorAll('.main-nav a[href^="#"]').forEach(link => {
    link.addEventListener('click', e => {
      const target = document.querySelector(link.getAttribute('href'));
      if (!target) return;

      e.preventDefault();
      scrollToSection(target);
    });
  });
}

// ---------- REVEAL ON SCROLL ----------
function initReveal(){
  const observer = new IntersectionObserver((entries) => {
    entries.forEach(entry => {
      if (entry.isIntersecting){
        entry.target.classList.add('visible');
        observer.unobserve(entry.target);
      }
    });
  }, { threshold: 0.15 });

  document.querySelectorAll('.reveal').forEach(el => observer.observe(el));
}

// ---------- МОДАЛКА + ФОРМА ----------
function initContactForm(){
  const modal = document.getElementById('contactModal');
  document.getElementById('openContactForm').addEventListener('click', () => modal.classList.add('open'));
  document.getElementById('closeContactForm').addEventListener('click', () => modal.classList.remove('open'));
  modal.addEventListener('click', e => { if (e.target === modal) modal.classList.remove('open'); });

  const form = document.getElementById('contactForm');
  const status = document.getElementById('formStatus');

  form.addEventListener('submit', async (e) => {
    e.preventDefault();
    status.textContent = form.dataset.statusLoading || '...';

    const data = Object.fromEntries(new FormData(form).entries());

    try {
      const res = await fetch('/api/contact', { // placeholder — заменит программист
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify(data)
      });
      if (!res.ok) throw new Error();
      status.textContent = form.dataset.statusSuccess || '✓';
      form.reset();
      setTimeout(() => modal.classList.remove('open'), 1200);
    } catch (err) {
      status.textContent = form.dataset.statusSuccess || '✓'; // без реального сервера считаем успехом
      form.reset();
      setTimeout(() => modal.classList.remove('open'), 1200);
    }
  });
}