/**
 * KIKO-style homepage promo carousel — progress bars, pause, video sync.
 */
export function initPromoSlider() {
  const root = document.querySelector("[data-promo-slider]");
  if (!(root instanceof HTMLElement)) return;

  const allSlides = [...root.querySelectorAll("[data-phs-slide]")];
  const allBars = [...root.querySelectorAll("[data-phs-goto]")];
  const allFills = [...root.querySelectorAll("[data-phs-fill]")];
  const isShown = (el) => el instanceof HTMLElement && getComputedStyle(el).display !== "none";
  const visibleIdx = allSlides
    .map((slide, i) => (isShown(slide) ? i : -1))
    .filter((i) => i >= 0);
  const slides = visibleIdx.map((i) => allSlides[i]);
  const bars = visibleIdx.map((i) => allBars[i]);
  const fills = visibleIdx.map((i) => allFills[i]);
  const toggle = root.querySelector("[data-phs-toggle]");
  const iconPause = root.querySelector(".phs-icon-pause");
  const iconPlay = root.querySelector(".phs-icon-play");
  if (!slides.length) return;

  const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
  let index = 0;
  let paused = reduce;
  let raf = 0;
  let startedAt = 0;
  let elapsed = 0;

  const durationOf = (i) => {
    const raw = Number(slides[i]?.getAttribute("data-phs-duration") || 6500);
    return Number.isFinite(raw) && raw > 0 ? raw : 6500;
  };

  const setToggleUi = () => {
    if (toggle instanceof HTMLElement) {
      toggle.setAttribute("aria-pressed", paused ? "true" : "false");
      toggle.setAttribute("aria-label", paused ? "پخش اسلایدر" : "توقف اسلایدر");
    }
    if (iconPause instanceof HTMLElement) iconPause.hidden = paused;
    if (iconPlay instanceof HTMLElement) iconPlay.hidden = !paused;
  };

  const syncVideo = (activeIndex) => {
    slides.forEach((slide, i) => {
      const video = slide.querySelector("[data-phs-video]");
      if (!(video instanceof HTMLVideoElement)) return;
      if (i === activeIndex && !paused) {
        video.muted = true;
        const p = video.play();
        if (p && typeof p.catch === "function") p.catch(() => {});
      } else {
        try {
          video.pause();
        } catch {
          /* ignore */
        }
      }
    });
  };

  const setProgress = (i, ratio) => {
    fills.forEach((fill, fi) => {
      if (!(fill instanceof HTMLElement)) return;
      let w = 0;
      if (fi < i) w = 1;
      else if (fi === i) w = Math.min(1, Math.max(0, ratio));
      fill.style.transform = `scaleX(${w})`;
    });
  };

  const show = (next) => {
    const i = ((next % slides.length) + slides.length) % slides.length;
    index = i;
    elapsed = 0;
    startedAt = performance.now();

    slides.forEach((slide, si) => {
      const on = si === i;
      slide.classList.toggle("is-active", on);
      slide.setAttribute("aria-hidden", on ? "false" : "true");
    });
    bars.forEach((bar, bi) => bar.classList.toggle("is-active", bi === i));
    setProgress(i, 0);
    syncVideo(i);
  };

  const tick = (now) => {
    raf = 0;
    if (paused) return;
    elapsed = now - startedAt;
    const dur = durationOf(index);
    setProgress(index, elapsed / dur);
    if (elapsed >= dur) {
      show(index + 1);
    }
    raf = requestAnimationFrame(tick);
  };

  const start = () => {
    if (paused || reduce) return;
    if (!raf) {
      startedAt = performance.now() - elapsed;
      raf = requestAnimationFrame(tick);
    }
  };

  const stop = () => {
    if (raf) {
      cancelAnimationFrame(raf);
      raf = 0;
    }
  };

  bars.forEach((bar, i) => {
    bar.addEventListener("click", () => {
      stop();
      show(i);
      start();
    });
  });

  toggle?.addEventListener("click", () => {
    paused = !paused;
    setToggleUi();
    if (paused) {
      stop();
      elapsed = performance.now() - startedAt;
      syncVideo(index);
    } else {
      start();
      syncVideo(index);
    }
  });

  // Pause autoplay when off-screen
  const io = new IntersectionObserver(
    (entries) => {
      const e = entries[0];
      if (!e) return;
      if (!e.isIntersecting) {
        stop();
        syncVideo(-1);
      } else if (!paused) {
        start();
        syncVideo(index);
      }
    },
    { threshold: 0.2 }
  );
  io.observe(root);

  setToggleUi();
  show(0);
  if (!reduce) start();
}