import {
  html, useState, useEffect, useRef, useMemo, useCallback,
} from './vendor/htm-preact.js';
import { t } from './i18n.js';
import { Icon } from './icon.js';
import { formatSize, pipelinedDownload } from './file-utils.js';

// ── Videos ───────────────────────────────────────────────────────────────────
//
// A poster-grid (TMDB-enriched) or flat (thumbnail-only) browser for a
// group's video files, per docs/mediacenter.md. Grouping: one card per movie,
// one card per show — shows are grouped by `display_title` (already
// resolved/corroborated at index time, §3.4), not by folder path, since a
// client-side path convention would have to guess how many roots/subfolders
// deep a show folder sits, which display_title already settled once.
//
// TMDB metadata is fetched lazily, only for a tile once it is actually
// visible (LazyTile below) — apps.md §5's virtualization requirement for a
// grid of many tiles. Thumbnails go through the same `file_req`/chunk path
// as a real file (docs/mediacenter.md §5.3) via MediaThumb, reusing
// chat-app.js's ChatImage pattern.

const VIEW_MODE_KEY = 'meshbay_video_view_mode';

function loadViewMode() {
  try { return localStorage.getItem(VIEW_MODE_KEY) === 'flat' ? 'flat' : 'poster'; }
  catch { return 'poster'; }
}
function saveViewMode(mode) {
  try { localStorage.setItem(VIEW_MODE_KEY, mode); } catch { /* per-device convenience only */ }
}

function formatDuration(seconds) {
  if (!seconds) return '';
  const total = Math.round(seconds);
  const h = Math.floor(total / 3600);
  const m = Math.floor((total % 3600) / 60);
  return h > 0 ? `${h}h${String(m).padStart(2, '0')}` : `${m}min`;
}

function formatResolution(width, height) {
  if (!width || !height) return '';
  if (height >= 2100) return '4K';
  if (height >= 1000) return `${height}p`;
  return `${width}x${height}`;
}

function yearOf(dateStr) {
  return dateStr ? String(dateStr).slice(0, 4) : '';
}

// ── grouping ─────────────────────────────────────────────────────────────────

// Nothing shows until an operator has actually chosen a root in Settings
// (§5.6/V-whatever this is now): the node itself runs no TMDB/thumbnail
// work for this group before that either (daemon.py's
// _enrich_new_video_entries), so falling back to "the whole index" here
// would just show files nothing has enriched.
function underVideoRoot(entry, videoRoot) {
  if (!videoRoot) return false;
  const p = entry.path || '';
  return p === videoRoot || p.startsWith(videoRoot + '/');
}

function buildSeasons(episodes) {
  const sorted = [...episodes].sort((a, b) => (a.season - b.season) || (a.episode - b.episode));
  const bySeason = new Map();
  for (const ep of sorted) {
    if (!bySeason.has(ep.season)) bySeason.set(ep.season, []);
    bySeason.get(ep.season).push(ep);
  }
  return [...bySeason.entries()].sort((a, b) => a[0] - b[0])
    .map(([season, seasonEpisodes]) => ({ season, episodes: seasonEpisodes }));
}

function groupVideoEntries(entries, videoRoot) {
  const movies = [];
  const showsByTitle = new Map();
  for (const e of entries) {
    if (e.type !== 'video') continue;
    if (!underVideoRoot(e, videoRoot)) continue;
    if (e.season != null && e.episode != null) {
      const title = e.display_title || e.name;
      if (!showsByTitle.has(title)) showsByTitle.set(title, { title, episodes: [] });
      showsByTitle.get(title).episodes.push(e);
    } else {
      movies.push(e);
    }
  }
  movies.sort((a, b) => (a.display_title || a.name).localeCompare(b.display_title || b.name));
  const shows = [...showsByTitle.values()].sort((a, b) => a.title.localeCompare(b.title));
  for (const show of shows) {
    show.episodes.sort((a, b) => (a.season - b.season) || (a.episode - b.episode));
    show.seasons = buildSeasons(show.episodes);
  }
  return { movies, shows };
}

// ── lazy-mount tile (apps.md §5 virtualization) ─────────────────────────────

const LAZY_TILE_MARGIN = 300;

function LazyTile({ cls = 'video-tile-slot', children }) {
  const ref = useRef(null);
  const [visible, setVisible] = useState(false);

  useEffect(() => {
    if (visible || !ref.current) return;
    // A tile that is already on screen (or within the margin) the moment
    // it mounts — the overwhelmingly common case, since a merge (§V6) or a
    // tab revisit mounts tiles into a grid that was already scrolled to
    // wherever the operator was looking — doesn't need to wait for
    // IntersectionObserver's own first callback at all: that first
    // delivery is only a *microtask/next-paint* guarantee, not an
    // immediate one, and was observed live taking upwards of 30 seconds
    // (matching the browser's own periodic intersection-computation
    // cadence exactly) — which read as "the poster never finishes
    // loading" even though every fetch behind it had already completed.
    // Checked synchronously so a genuinely below-the-fold tile still only
    // mounts once actually scrolled near.
    const rect = ref.current.getBoundingClientRect();
    const viewportHeight = window.innerHeight || document.documentElement.clientHeight;
    const alreadyNear = rect.bottom >= -LAZY_TILE_MARGIN && rect.top <= viewportHeight + LAZY_TILE_MARGIN;
    if (alreadyNear) { setVisible(true); return; }
    const obs = new IntersectionObserver((obsEntries) => {
      if (obsEntries.some((oe) => oe.isIntersecting)) { setVisible(true); obs.disconnect(); }
    }, { rootMargin: `${LAZY_TILE_MARGIN}px` });
    obs.observe(ref.current);
    return () => obs.disconnect();
  }, [visible]);

  return html`<div ref=${ref} class=${cls}>${visible ? children : null}</div>`;
}

// ── thumbnail/poster image, decrypted via the chunk path ────────────────────
//
// Cached per session by thumb_hash (a content hash, so it never goes stale):
// the same poster reused across a season's worth of episode tiles is
// decrypted once, not once per tile. Blob URLs are not revoked — the number
// of distinct thumbnails one session ever visits is bounded by the library
// size, and reference-counting revocation across many tile mounts/unmounts
// would cost real complexity for a benefit that only matters in a very long
// session.
const _thumbBlobCache = new Map();

function MediaThumb({
  thumbHash, transportRef, gekRef, alt, cls = 'video-thumb', onReady, emptyIcon = 'video',
}) {
  const [blobUrl, setBlobUrl] = useState(() => _thumbBlobCache.get(thumbHash) || null);
  const [retryToken, setRetryToken] = useState(0);

  useEffect(() => {
    const listener = () => setRetryToken((n) => n + 1);
    _thumbRetryListeners.add(listener);
    return () => _thumbRetryListeners.delete(listener);
  }, []);

  // Re-checks the cache by the CURRENT thumbHash on every change rather than
  // trusting the `blobUrl` state variable — a PosterCard swaps this same
  // component instance's thumbHash prop from the raw fallback frame to the
  // TMDB poster once metadata resolves, and gating on "is blobUrl already
  // set" (from the *previous* hash) would leave the fallback frame on
  // screen forever instead of ever fetching the poster.
  //
  // `onReady` fires exactly once per settled thumbHash — cache hit, fetch
  // success, fetch failure, or no hash at all — so a caller that hides this
  // component until its image has actually arrived (PosterCard) always
  // gets unstuck, even when there's nothing to show.
  useEffect(() => {
    const cached = _thumbBlobCache.get(thumbHash);
    if (cached) { setBlobUrl(cached); if (onReady) onReady(cached); return; }
    setBlobUrl(null);
    if (!thumbHash) { if (onReady) onReady(null); return; }
    let cancelled = false;
    (async () => {
      const transport = transportRef.current;
      if (!transport || !transport.connected) { if (onReady) onReady(null); return; }
      try {
        const chunks = await pipelinedDownload(transport, gekRef.current, thumbHash, 1);
        if (cancelled) return;
        const url = URL.createObjectURL(new Blob(chunks, { type: 'image/jpeg' }));
        _thumbBlobCache.set(thumbHash, url);
        setBlobUrl(url);
        if (onReady) onReady(url);
      } catch {
        /* leave the placeholder — a transient fetch failure isn't an error state */
        if (!cancelled && onReady) onReady(null);
      }
    })();
    return () => { cancelled = true; };
  }, [thumbHash, retryToken]);

  if (!blobUrl) return html`<div class="${cls} video-thumb-empty"><${Icon} name=${emptyIcon} /></div>`;
  return html`<img class=${cls} src=${blobUrl} alt=${alt || ''} loading="lazy" />`;
}

// ── TMDB metadata, fetched once per visible tile ────────────────────────────

// An operator correcting a wrong match (TmdbSearchOverlay below) changes
// what `media_meta_req` returns for a file every already-mounted tile/modal
// already has cached in its own useMediaMeta state — nothing would ever
// refetch otherwise, since fileId/active don't change. Bumping this and
// telling every subscribed hook to redo its fetch is simpler than trying to
// know which files a given override actually affects (that's server-side
// knowledge — display_title grouping — this module doesn't have).
const _mediaMetaListeners = new Set();
function bumpMediaMetaGeneration() {
  for (const fn of _mediaMetaListeners) fn();
}

const _thumbRetryListeners = new Set();
function bumpThumbGeneration() {
  for (const fn of _thumbRetryListeners) fn();
}

function useMediaMeta(transportRef, fileId, active) {
  const [meta, setMeta] = useState(null);
  const [refetchToken, setRefetchToken] = useState(0);

  useEffect(() => {
    // Clears immediately (so the spinner shows right away, not only once
    // the new fetch resolves) and bumps the token, which re-runs the fetch
    // effect below regardless of whether fileId/active changed at all.
    const listener = () => { setMeta(null); setRefetchToken((n) => n + 1); };
    _mediaMetaListeners.add(listener);
    return () => _mediaMetaListeners.delete(listener);
  }, []);

  useEffect(() => {
    if (!active || !fileId) return;
    let cancelled = false;
    (async () => {
      const transport = transportRef.current;
      if (!transport || !transport.connected) return;
      try {
        const resp = await transport.fetchMediaMeta(fileId);
        if (!cancelled) setMeta(resp);
      } catch { if (!cancelled) setMeta({ confidence: 0 }); }
    })();
    return () => { cancelled = true; };
  }, [fileId, active, refetchToken]);
  return meta;
}

// ── per-season TMDB metadata (overview/air_date/poster), season-tab view ───
//
// Found live: a show's own tmdb_meta.overview is one static field that does
// not necessarily describe every season alike (a season-3-specific
// promotional summary read as the synopsis for all three seasons). Cached
// for the session by tmdb_id+season, mirroring _thumbBlobCache — the same
// season is revisited every time its tab is reselected.
const _seasonMetaCache = new Map();

function useSeasonMeta(transportRef, tmdbId, season, active) {
  const cacheKey = active && tmdbId != null && season != null ? `${tmdbId}:${season}` : null;
  const [meta, setMeta] = useState(() => (cacheKey ? _seasonMetaCache.get(cacheKey) || null : null));
  useEffect(() => {
    if (!cacheKey) return;
    const cached = _seasonMetaCache.get(cacheKey);
    if (cached) { setMeta(cached); return; }
    setMeta(null);
    let cancelled = false;
    (async () => {
      const transport = transportRef.current;
      if (!transport || !transport.connected) return;
      try {
        const resp = await transport.fetchSeasonMeta(tmdbId, season);
        if (cancelled) return;
        _seasonMetaCache.set(cacheKey, resp);
        setMeta(resp);
      } catch { if (!cancelled) setMeta({ confidence: 0 }); }
    })();
    return () => { cancelled = true; };
  }, [cacheKey]);
  return meta;
}

// ── Mode A: poster grid ──────────────────────────────────────────────────────

function PosterCard({ title, subtitle, repEntry, transportRef, gekRef, onOpen, groupKey, onMetaResolved }) {
  const tRef = repEntry._tRef || transportRef;
  const gRef = repEntry._gRef || gekRef;
  const meta = useMediaMeta(tRef, repEntry.id, true);
  const confident = Boolean(meta && meta.confidence && meta.tmdb_id);
  const metaReady = meta !== null;

  // Reports this tile's own resolution upward so PosterGrid can notice two
  // differently-parsed folders (a show split across release groups that
  // named its seasons inconsistently, §3.4/V6) resolving to the same TMDB
  // id, and merge them into one card — never required for the generic
  // per-folder display to work, only an enhancement once it's known safe.
  useEffect(() => {
    if (meta && onMetaResolved) onMetaResolved(groupKey, meta);
  }, [meta, groupKey]);

  const posterHash = confident && meta.poster_thumb_hash ? meta.poster_thumb_hash : repEntry.thumb_hash;

  // Which hash MediaThumb has actually confirmed ready — compared against
  // the *current* posterHash below, rather than a separate boolean reset
  // by its own effect on posterHash change. That second-writer shape had a
  // real bug: the instant metaReady flips true, posterHash jumps from the
  // raw fallback frame to the resolved poster in the very same commit that
  // mounts MediaThumb for it — and when that poster's bytes are already in
  // MediaThumb's session cache (a revisit within the same tab, no reload),
  // its onReady fires synchronously from that same mount effect. Effects
  // run children-first, so the "reset on posterHash change" effect fired
  // *after* it, in the same commit, unconditionally setting the flag back
  // to false — with no later event left to ever set it true again. The
  // card stayed a spinner forever despite the image already being loaded.
  // Deriving readiness from a direct comparison has no such ordering to
  // get wrong: whichever of the two fires, in whichever order, the render
  // that follows sees the same answer.
  const [readyHash, setReadyHash] = useState(null);
  const handleImageReady = useCallback(() => setReadyHash(posterHash), [posterHash]);
  const imageReady = readyHash === posterHash;

  // Nothing is shown until BOTH the TMDB lookup and the final chosen image
  // (the poster once matched, the file's own frame otherwise) have
  // actually settled. Revealing the raw per-file frame first and swapping
  // it for the poster a moment later — or showing a card that a moment
  // later gets absorbed into a neighbour once §V6's merge kicks in — was
  // exactly the flash an operator flagged as hard on the eyes. A slow
  // lookup (a big, freshly-scanned library) just means the spinner stays a
  // little longer, never a partially-drawn card.
  const ready = metaReady && imageReady;

  return html`
    <div class="video-card ${ready && !confident ? 'video-card-unmatched' : ''}" onClick=${onOpen}>
      ${!ready && html`
        <div class="video-poster video-poster-loading"><span class="spinner"></span></div>
      `}
      <div class="video-poster-slot" style=${ready ? '' : 'display:none'}>
        ${metaReady && html`
          <${MediaThumb} thumbHash=${posterHash} alt=${title}
            cls="video-poster" transportRef=${tRef} gekRef=${gRef}
            onReady=${handleImageReady} />
        `}
      </div>
      ${ready && html`
        <div class="video-card-info">
          <div class="video-card-title">
            ${(confident && meta.title) || title}
            ${!confident && html`<span class="video-card-flag" title=${t('video.no_match')}>?</span>`}
          </div>
          <div class="video-card-sub">
            ${confident && meta.release_date ? yearOf(meta.release_date) : ''}
            ${confident && meta.first_air_date ? yearOf(meta.first_air_date) : ''}
            ${subtitle ? ` · ${subtitle}` : ''}
          </div>
          ${repEntry.groupName && html`
            <div class="video-card-group">${repEntry.groupName}</div>
          `}
        </div>
      `}
    </div>
  `;
}

// ── season tab bar (docs/mediacenter.md §5.4's fix for a mis-scoped overview) ─

function SeasonTabs({ seasons, selected, onSelect }) {
  return html`
    <div class="video-season-tabs">
      ${seasons.map((s) => html`
        <button key=${s.season}
          class="video-season-tab ${selected === s.season ? 'active' : ''}"
          onClick=${() => onSelect(s.season)}>
          ${s.season === 0 ? t('video.specials') : t('video.season_n', { n: s.season })}
        </button>
      `)}
    </div>
  `;
}

// ── operator: correct a wrong automatic TMDB match ──────────────────────────

// Same shape as group-settings.js's own signFn construction (setVideoRoot,
// setTmdbConfig, ...) — there is no group-wide "sign this" helper to share,
// each caller builds one from the connection it already has.
function buildSignFn(transportRef) {
  const transport = transportRef.current;
  const sk = transport && transport.sessionKeys && transport.sessionKeys.skEdB64;
  return (sk && window.MeshBayKeys)
    ? (transcript) => window.MeshBayKeys.signBytes(sk, transcript)
    : null;
}

function TmdbSearchOverlay({
  initialQuery, mediaType, fileId, transportRef, gekRef, onClose, onApplied,
}) {
  const [query, setQuery] = useState(initialQuery || '');
  const [results, setResults] = useState(null); // null = not searched yet
  const [searching, setSearching] = useState(false);
  const [applying, setApplying] = useState(false);
  const [error, setError] = useState('');

  const runSearch = useCallback(async (e) => {
    if (e) e.preventDefault();
    const q = query.trim();
    if (!q || searching) return;
    setSearching(true);
    setError('');
    try {
      const transport = transportRef.current;
      const resp = await transport.searchTmdb(mediaType, q);
      setResults(resp.results || []);
    } catch (err) {
      setError(err.message);
      setResults([]);
    } finally {
      setSearching(false);
    }
  }, [query, mediaType, transportRef, searching]);

  const apply = useCallback(async (tmdbId) => {
    if (applying) return;
    setApplying(true);
    setError('');
    try {
      const signFn = buildSignFn(transportRef);
      await transportRef.current.overrideTmdbMatch(fileId, tmdbId, mediaType, signFn);
      bumpMediaMetaGeneration();
      onApplied();
    } catch (err) {
      setError(err.message);
      setApplying(false);
    }
  }, [applying, fileId, mediaType, transportRef, onApplied]);

  return html`
    <div class="video-overlay video-search-overlay" onClick=${(e) => {
      if (e.target.classList.contains('video-search-overlay')) onClose();
    }}>
      <div class="video-detail video-search-panel">
        <div class="video-top-bar">
          <span class="video-title">${t('video.search_title')}</span>
          <button class="video-close" onClick=${onClose} title=${t('video.close')}>
            <${Icon} name="close" /></button>
        </div>
        <div class="video-detail-body">
          <form class="video-search-form" onSubmit=${runSearch}>
            <input type="text" value=${query} autofocus
              placeholder=${t('video.search_placeholder')}
              onInput=${(e) => setQuery(e.target.value)} />
            <button class="admin-btn" type="submit" disabled=${searching || !query.trim()}>
              ${searching ? html`<span class="spinner"></span>` : t('video.search_button')}
            </button>
          </form>
          <p class="video-search-hint">
            ${mediaType === 'tv' ? t('video.search_apply_hint') : t('video.search_apply_hint_movie')}
          </p>
          ${error && html`<p class="video-search-error">${error}</p>`}
          ${results && results.length === 0 && !searching && html`
            <p class="page-message">${t('video.search_no_results')}</p>
          `}
          ${results && results.length > 0 && html`
            <div class="video-search-results">
              ${results.map((r) => html`
                <button class="video-search-result" key=${r.tmdb_id}
                  disabled=${applying}
                  onClick=${() => apply(r.tmdb_id)}>
                  <div class="video-search-result-thumb">
                    <${MediaThumb} thumbHash=${r.poster_thumb_hash} alt=${r.title}
                      cls="video-search-result-poster" transportRef=${transportRef} gekRef=${gekRef} />
                  </div>
                  <div class="video-flat-info">
                    <div class="video-flat-title">${r.title}</div>
                    <div class="video-flat-sub">${r.year}</div>
                  </div>
                </button>
              `)}
            </div>
          `}
        </div>
      </div>
    </div>
  `;
}

function VideoDetailModal({
  title, meta, repEntry, show, files, transportRef, gekRef, onClose, onPlay, isNodeAdmin,
}) {
  const confident = Boolean(meta && meta.confidence && meta.tmdb_id);
  const [searching, setSearching] = useState(false);
  const [rematching, setRematching] = useState(false);
  const mediaType = show ? 'tv' : 'movie';

  // §10.1/V13: drop this file's cached match on the node and let it
  // re-resolve with the current matcher — the one-click alternative to the
  // full search-and-pick flow above.
  const doRematch = useCallback(async () => {
    if (rematching) return;
    setRematching(true);
    try {
      await transportRef.current.rematchTmdbMatch(repEntry.id, buildSignFn(transportRef));
      bumpMediaMetaGeneration();
    } catch { /* leave the current match in place */ }
    setRematching(false);
  }, [rematching, repEntry, transportRef]);

  // Reset whenever a different file/show is opened in this same modal
  // instance — repEntry/show change identity, selectedSeason must not
  // silently keep pointing at whatever the previous show's season 4 was.
  const [selectedSeason, setSelectedSeason] = useState(null);
  useEffect(() => {
    if (!show) { setSelectedSeason(null); return; }
    const preferred = repEntry.season != null && show.seasons.some((s) => s.season === repEntry.season)
      ? repEntry.season
      : (show.seasons.find((s) => s.season !== 0) || show.seasons[0]).season;
    setSelectedSeason(preferred);
  }, [show, repEntry]);

  const showMultiSeason = Boolean(show && show.seasons.length > 1);
  const seasonMeta = useSeasonMeta(
    transportRef, confident ? meta.tmdb_id : null, selectedSeason,
    showMultiSeason && Boolean(confident) && selectedSeason != null);
  const seasonConfident = showMultiSeason && seasonMeta && seasonMeta.confidence;

  return html`
    <div class="video-overlay" onClick=${(e) => {
      if (e.target.classList.contains('video-overlay')) onClose();
    }}>
      <div class="video-detail">
        <div class="video-top-bar">
          <span class="video-title">${(confident && meta.title) || title}</span>
          <button class="video-close" onClick=${onClose} title=${t('video.close')}>
            <${Icon} name="close" /></button>
        </div>
        <div class="video-detail-body">
          ${meta !== null && !confident && html`
            <p class="video-detail-nomatch">${t('video.no_match')}</p>
          `}
          <p class="video-detail-source">
            ${t('video.source_file', { name: `${repEntry.path}/${repEntry.name}` })}
            ${confident && html`<span class="video-detail-tmdbref"> · TMDB #${meta.tmdb_id}</span>`}
          </p>
          ${confident && html`
            <p class="video-detail-overview">${(seasonConfident && seasonMeta.overview) || meta.overview}</p>
            <p class="video-detail-facts">
              ${meta.vote_average ? `★ ${meta.vote_average.toFixed(1)}` : ''}
              ${meta.genres && meta.genres.length ? ` · ${meta.genres.join(', ')}` : ''}
              ${meta.director ? ` · ${t('video.director')}: ${meta.director}` : ''}
              ${seasonConfident && seasonMeta.air_date ? ` · ${yearOf(seasonMeta.air_date)}` : ''}
            </p>
            ${meta.cast && meta.cast.length > 0 && html`
              <p class="video-detail-cast">
                ${meta.cast.slice(0, 6).map((c) => c.name).join(', ')}
              </p>
            `}
          `}
          ${isNodeAdmin && html`
            <div class="video-admin-actions">
              <button class="admin-btn video-fix-match" onClick=${() => setSearching(true)}>
                ${t('video.fix_match')}
              </button>
              <button class="admin-btn" onClick=${doRematch} disabled=${rematching}>
                ${rematching ? html`<span class="spinner"></span>` : t('video.rematch_one')}
              </button>
            </div>
          `}
          ${showMultiSeason && html`
            <${SeasonTabs} seasons=${show.seasons} selected=${selectedSeason}
              onSelect=${setSelectedSeason} />
          `}
          ${!show && (!files || files.length <= 1) && html`
            <button class="admin-btn" onClick=${() => onPlay(repEntry)}>
              <${Icon} name="play" /> ${t('group.play')}
              ${repEntry.duration ? ` (${formatDuration(repEntry.duration)})` : ''}
            </button>
          `}
          ${!show && files && files.length > 1 && html`
            <div class="video-version-list">
              ${[...files]
                .sort((a, b) => (b.height || 0) - (a.height || 0) || (b.size || 0) - (a.size || 0))
                .map((f) => html`
                <button class="video-episode-row" key=${f.id} onClick=${() => onPlay(f)}>
                  <${Icon} name="play" />
                  <span class="video-episode-label">
                    ${[formatResolution(f.width, f.height), formatDuration(f.duration),
                       formatSize(f.size)].filter(Boolean).join(' · ')}
                  </span>
                </button>
              `)}
            </div>
          `}
          ${show && html`
            <div class="video-season-list">
              ${(showMultiSeason ? show.seasons.filter((s) => s.season === selectedSeason) : show.seasons)
                .map((s) => html`
                <div class="video-season" key=${s.season}>
                  ${!showMultiSeason && html`
                    <div class="video-season-header">
                      ${s.season === 0 ? t('video.specials') : t('video.season_n', { n: s.season })}
                    </div>
                  `}
                  ${s.episodes.map((ep) => html`
                    <button class="video-episode-row" key=${ep.id} onClick=${() => onPlay(ep)}>
                      <${LazyTile} cls="video-episode-thumb-slot">
                        <${MediaThumb} thumbHash=${ep.thumb_hash} alt=${ep.display_title || ep.name}
                          cls="video-episode-thumb" transportRef=${ep._tRef || transportRef} gekRef=${ep._gRef || gekRef} />
                      </${LazyTile}>
                      <span class="video-episode-label">
                        S${ep.season}E${String(ep.episode).padStart(2, '0')}
                        ${' · '}${ep.display_title || ep.name}
                      </span>
                      <span class="video-episode-meta">
                        ${formatDuration(ep.duration)} ${formatResolution(ep.width, ep.height)}
                      </span>
                    </button>
                  `)}
                </div>
              `)}
            </div>
          `}
        </div>
      </div>
    </div>
    ${searching && html`
      <${TmdbSearchOverlay} initialQuery=${(confident && meta.title) || title} mediaType=${mediaType}
        fileId=${repEntry.id} transportRef=${transportRef} gekRef=${gekRef}
        onClose=${() => setSearching(false)}
        onApplied=${() => setSearching(false)} />
    `}
  `;
}

function PosterGrid({ movies, shows, transportRef, gekRef, onPreview, tmdbEnabled, isNodeAdmin }) {
  const [detail, setDetail] = useState(null); // { title, repEntry, show? }
  // raw (per-folder-parsed-title) show title -> its own resolved media_meta_resp.
  const [metaByGroup, setMetaByGroup] = useState({});

  const handleMetaResolved = useCallback((groupKey, meta) => {
    setMetaByGroup((prev) => (prev[groupKey] === meta ? prev : { ...prev, [groupKey]: meta }));
  }, []);

  // Two raw groups (grouped by parsed display_title, §4.1) resolving to the
  // same confident TMDB id are almost certainly one show whose seasons
  // were released under differently-named folders — confirmed live: one
  // operator's show had its two seasons parsed as "Ovni" and "OVNIs" by
  // two different release groups, showing as two identical-looking cards
  // once both matched the same real show (§3.4/V6). Merged here once both
  // are actually known — never required for the fallback to work: a group
  // with no confident match yet, or ever, still shows on its own, exactly
  // the generic per-folder display needs.
  const mergedShows = useMemo(() => {
    const byTmdbId = new Map();
    const standalone = [];
    for (const s of shows) {
      const meta = metaByGroup[s.title];
      const tmdbId = meta && meta.confidence && meta.tmdb_id;
      if (tmdbId) {
        if (!byTmdbId.has(tmdbId)) byTmdbId.set(tmdbId, []);
        byTmdbId.get(tmdbId).push(s);
      } else {
        standalone.push([s]);
      }
    }
    return [...byTmdbId.values(), ...standalone].map((groups) => {
      const episodes = groups.flatMap((g) => g.episodes);
      return {
        // groups[0].title, not a joined string of every constituent's
        // title: a fresh key here would make this a brand-new PosterCard
        // (and LazyTile) the instant a second raw group merges into an
        // already-visible one — throwing away its already-fired
        // IntersectionObserver and already-resolved metadata/poster for no
        // reason, and reintroducing exactly the flash the "ready" gating
        // above exists to prevent. groups[0].title is already unique
        // (raw titles are, via groupVideoEntries' showsByTitle) and, for
        // the overwhelmingly common unmerged case, is the same key the
        // card already had — so nothing about this changes when no merge
        // ever happens.
        key: groups[0].title,
        title: groups[0].title,
        episodes,
        seasons: buildSeasons(episodes),
      };
    });
  }, [shows, metaByGroup]);

  // The movie counterpart of mergedShows (§10.1/V12): two files that TMDB
  // resolves to the same id — the usual case being one film present at two
  // resolutions, or the same rip in two folders — collapse to one card
  // whose detail modal lists the versions. Same keying discipline as
  // mergedShows: the first constituent's id is stable and unique, so an
  // unmerged movie keeps the exact key its card already had and a merge
  // updates props instead of remounting (which would throw away an
  // already-resolved poster).
  const mergedMovies = useMemo(() => {
    const byTmdbId = new Map();
    const standalone = [];
    for (const e of movies) {
      const meta = metaByGroup[`movie:${e.id}`];
      const tmdbId = meta && meta.confidence && meta.tmdb_id;
      if (tmdbId) {
        if (!byTmdbId.has(tmdbId)) byTmdbId.set(tmdbId, []);
        byTmdbId.get(tmdbId).push(e);
      } else {
        standalone.push([e]);
      }
    }
    return [...byTmdbId.values(), ...standalone].map((files) => ({
      key: `movie:${files[0].id}`,
      title: files[0].display_title || files[0].name,
      files,
    }));
  }, [movies, metaByGroup]);

  const openDetail = (title, repEntry, show, files) => setDetail({ title, repEntry, show, files });
  const detailTRef = detail && detail.repEntry._tRef ? detail.repEntry._tRef : transportRef;
  const detailGRef = detail && detail.repEntry._gRef ? detail.repEntry._gRef : gekRef;
  const detailMeta = useMediaMeta(detailTRef, detail ? detail.repEntry.id : null, !!detail);

  return html`
    <div class="video-grid">
      ${mergedMovies.map((m) => {
        const repEntry = m.files.find((e) => e.thumb_hash) || m.files[0];
        const subtitle = m.files.length > 1
          ? t('video.versions', { n: m.files.length })
          : formatDuration(repEntry.duration);
        // With TMDB off and only one file there is nothing the detail modal
        // would add for a movie (no overview, no season list) — straight to
        // the player. More than one file always needs the version picker.
        const straightToPlayer = !tmdbEnabled && m.files.length === 1;
        return html`
        <${LazyTile} key=${m.key}>
          <${PosterCard} title=${m.title}
            subtitle=${subtitle} repEntry=${repEntry}
            groupKey=${`movie:${m.files[0].id}`}
            onMetaResolved=${handleMetaResolved}
            transportRef=${transportRef} gekRef=${gekRef}
            onOpen=${() => (straightToPlayer
              ? onPreview(repEntry)
              : openDetail(m.title, repEntry, null, m.files))} />
        </${LazyTile}>
      `; })}
      ${mergedShows.map((s) => {
        // Prefer an episode that actually has a thumbnail over blindly
        // episodes[0]: if that specific file's enrichment hasn't produced
        // one yet (or failed), the card showed an empty placeholder even
        // though sibling episodes — visible right there in Flat list —
        // have one. The TMDB path (or its absence) is the same regardless
        // of which episode's own file supplies the fallback frame.
        const repEntry = s.episodes.find((e) => e.thumb_hash) || s.episodes[0];
        // Known up front from the already-parsed index fields (§3.4), no
        // TMDB needed: a card covering exactly one season says so before
        // a click, rather than an anonymous episode count — the generic
        // "N episodes" stays for a merged, multi-season, or special-only
        // card, where a single number would misrepresent it.
        const singleSeason = s.seasons.length === 1 ? s.seasons[0].season : null;
        const subtitle = singleSeason != null
          ? (singleSeason === 0 ? t('video.specials') : t('video.season_n', { n: singleSeason }))
          : t('video.n_episodes', { n: s.episodes.length });
        return html`
        <${LazyTile} key=${s.key}>
          <${PosterCard} title=${s.title}
            subtitle=${subtitle}
            repEntry=${repEntry}
            groupKey=${s.title}
            onMetaResolved=${handleMetaResolved}
            transportRef=${transportRef} gekRef=${gekRef}
            onOpen=${() => openDetail(s.title, repEntry, s)} />
        </${LazyTile}>
      `; })}
    </div>
    ${detail && html`
      <${VideoDetailModal} title=${detail.title} meta=${detailMeta}
        repEntry=${detail.repEntry} show=${detail.show} files=${detail.files}
        transportRef=${detailTRef} gekRef=${detailGRef} isNodeAdmin=${isNodeAdmin}
        onClose=${() => setDetail(null)}
        onPlay=${(entry) => { setDetail(null); onPreview(entry); }} />
    `}
  `;
}

// ── Mode B: flat, thumbnail-only, no TMDB ────────────────────────────────────

// Within a season group, every episode's own display_title is usually
// just the show name again (guessit rarely finds a per-episode subtitle
// for this kind of release) — repeating "OVNI" twelve times in a row said
// nothing an episode number wouldn't say better. Shown only when this row
// is actually inside a season group (`seasonContext` set); a real,
// distinct per-episode title (a show that *does* carry one) still wins
// over the generic "Episode N" label.
function FlatMovieRow({ entry, transportRef, gekRef, onPreview, seasonContext }) {
  const tRef = entry._tRef || transportRef;
  const gRef = entry._gRef || gekRef;
  const isEpisode = seasonContext && entry.season != null && entry.episode != null;
  const hasOwnTitle = entry.display_title && entry.display_title !== seasonContext;
  const label = isEpisode
    ? (hasOwnTitle ? `${t('video.episode_n', { n: entry.episode })} · ${entry.display_title}`
                   : t('video.episode_n', { n: entry.episode }))
    : (entry.display_title || entry.name);

  return html`
    <div class="video-flat-row" onClick=${() => onPreview(entry)}>
      <${LazyTile} cls="video-flat-thumb-slot">
        <${MediaThumb} thumbHash=${entry.thumb_hash} alt=${entry.display_title || entry.name}
          cls="video-flat-thumb" transportRef=${tRef} gekRef=${gRef} />
      </${LazyTile}>
      <div class="video-flat-info">
        <div class="video-flat-title">${label}</div>
        <div class="video-flat-sub">
          ${formatDuration(entry.duration)} ${formatResolution(entry.width, entry.height)}
          ${' · '}${formatSize(entry.size)}
        </div>
      </div>
      ${entry.groupName && html`
        <a href="#/group/${entry.groupId}" class="badge search-group-badge"
          onClick=${(e) => e.stopPropagation()}>${entry.groupName}</a>
      `}
    </div>
  `;
}

function FlatShowFolder({ show, transportRef, gekRef, onPreview }) {
  const [open, setOpen] = useState(false);
  return html`
    <div class="video-flat-folder">
      <div class="video-flat-row" onClick=${() => setOpen((v) => !v)}>
        <div class="video-flat-thumb video-thumb-empty"><${Icon} name="folder" /></div>
        <div class="video-flat-info">
          <div class="video-flat-title">${show.title}</div>
          <div class="video-flat-sub">${t('video.n_episodes', { n: show.episodes.length })}</div>
        </div>
        <${Icon} name="chevron" cls=${open ? 'video-flat-chevron open' : 'video-flat-chevron'} />
      </div>
      ${open && show.seasons.map((s) => html`
        <div class="video-flat-season" key=${s.season}>
          <div class="video-season-header">
            ${s.season === 0 ? t('video.specials') : t('video.season_n', { n: s.season })}
          </div>
          ${s.episodes.map((ep) => html`
            <${FlatMovieRow} key=${ep.id} entry=${ep} seasonContext=${show.title}
              transportRef=${transportRef} gekRef=${gekRef} onPreview=${onPreview} />
          `)}
        </div>
      `)}
    </div>
  `;
}

function FlatList({ movies, shows, transportRef, gekRef, onPreview }) {
  const items = [
    ...movies.map((e) => ({ key: e.display_title || e.name, kind: 'movie', entry: e })),
    ...shows.map((s) => ({ key: s.title, kind: 'show', show: s })),
  ].sort((a, b) => a.key.localeCompare(b.key));

  return html`
    <div class="video-flat-list">
      ${items.map((it) => it.kind === 'movie'
        ? html`<${FlatMovieRow} key=${it.entry.id} entry=${it.entry}
            transportRef=${transportRef} gekRef=${gekRef} onPreview=${onPreview} />`
        : html`<${FlatShowFolder} key=${it.show.title} show=${it.show}
            transportRef=${transportRef} gekRef=${gekRef} onPreview=${onPreview} />`)}
    </div>
  `;
}

// ── shell ────────────────────────────────────────────────────────────────────

function VideoApp({
  groupId, transportRef, gekRef, status, entries, onPreview, videoRoot, tmdbConfig, isNodeAdmin,
  hideFilter,
}) {
  const [mode, setMode] = useState(loadViewMode);
  const [filter, setFilter] = useState('');
  // Which of movies/shows to show at all — independent of the text filter
  // below, and applied first: a title match within a type nobody asked to
  // see is still not what "Movies only" means.
  const [typeFilter, setTypeFilter] = useState('all');
  const tmdbEnabled = tmdbConfig ? tmdbConfig.enabled : true;

  useEffect(() => { setMode(loadViewMode()); }, [groupId]);
  useEffect(() => { setFilter(''); setTypeFilter('all'); }, [groupId]);

  const setModeAndSave = (m) => { setMode(m); saveViewMode(m); };

  const { movies, shows } = useMemo(
    () => groupVideoEntries(entries, videoRoot), [entries, videoRoot]);

  const needle = filter.trim().toLowerCase();
  const filteredMovies = useMemo(() => (typeFilter === 'series' ? [] : !needle ? movies : movies.filter(
    (e) => (e.display_title || e.name).toLowerCase().includes(needle))), [movies, needle, typeFilter]);
  const filteredShows = useMemo(() => (typeFilter === 'movies' ? [] : !needle ? shows : shows.filter(
    (s) => s.title.toLowerCase().includes(needle))), [shows, needle, typeFilter]);

  return html`
    ${(status === 'discovering' || status === 'connecting' || status === 'fetching') && html`
      <p class="page-message"><span class="spinner"></span>${' '}${t('status.connecting_short')}</p>
    `}
    ${status === 'offline' && html`
      <p class="page-message">${t('group.offline_title')} ${t('group.offline_hint')}</p>
    `}
    ${status === 'connected' && !videoRoot && html`
      <p class="page-message">${t('video.no_root_configured')}</p>
    `}
    ${status === 'connected' && videoRoot && html`
      <div class="video-toolbar">
        <button class="tb-btn ${mode === 'poster' ? 'active' : ''}"
          onClick=${() => setModeAndSave('poster')}>
          ${t('video.mode_poster')}
        </button>
        <button class="tb-btn ${mode === 'flat' ? 'active' : ''}"
          onClick=${() => setModeAndSave('flat')}>
          ${t('video.mode_flat')}
        </button>
        <div class="tb-typefilter">
          <button class=${typeFilter === 'all' ? 'active' : ''}
            onClick=${() => setTypeFilter('all')}>
            ${t('video.filter_all')}
          </button>
          <button class=${typeFilter === 'movies' ? 'active' : ''}
            onClick=${() => setTypeFilter('movies')}>
            ${t('video.filter_movies')}
          </button>
          <button class=${typeFilter === 'series' ? 'active' : ''}
            onClick=${() => setTypeFilter('series')}>
            ${t('video.filter_series')}
          </button>
        </div>
        ${!hideFilter && html`<div class="tb-search">
          <${Icon} name="search" />
          <input type="text" placeholder="${t('group.filter')}"
            value=${filter} onInput=${(e) => setFilter(e.target.value)} />
        </div>`}
      </div>
      ${filteredMovies.length === 0 && filteredShows.length === 0 && html`
        <p class="page-message">${needle ? t('group.empty_filter') : t('video.empty')}</p>
      `}
      ${mode === 'poster'
        ? html`<${PosterGrid} movies=${filteredMovies} shows=${filteredShows}
                transportRef=${transportRef} gekRef=${gekRef} onPreview=${onPreview}
                tmdbEnabled=${tmdbEnabled} isNodeAdmin=${isNodeAdmin} />`
        : html`<${FlatList} movies=${filteredMovies} shows=${filteredShows}
                transportRef=${transportRef} gekRef=${gekRef} onPreview=${onPreview} />`}
    `}
  `;
}

// MediaThumb and LazyTile are also used by music-app.js (docs/musicbay.md
// §7.1): the same "decrypt a thumb_hash via the chunk path into a cached
// blob" and "mount only once actually scrolled near" mechanisms apply to a
// track's cover art unchanged, so Music imports them here rather than
// re-implementing (apps.md §4's checklist).
export { VideoApp, MediaThumb, LazyTile, groupVideoEntries, bumpMediaMetaGeneration, bumpThumbGeneration };