// Rehearser playback, transport, and persistent line-audio cache.
// Loaded before rehearser.js; handlers resolve shared state and helpers at call time.

// ── WebAudio pre-decode (eliminates 2-3s silence between lines) ─────────────

let _rehPlayCtx   = null;
const rehDecodedBuffers = new Map(); // lineIndex → AudioBuffer (pre-decoded PCM)
let rehCurrentSource  = null;        // active AudioBufferSourceNode
let rehWordHighlightRaf = null;

function rehPlayCtx() {
  if (!_rehPlayCtx) _rehPlayCtx = new (window.AudioContext || window.webkitAudioContext)();
  if (_rehPlayCtx.state === 'suspended') _rehPlayCtx.resume().catch(() => {});
  return _rehPlayCtx;
}

// Decoded PCM (Float32) is the heaviest cache and is re-derivable from the cached
// blob, so keep only a sliding window around the playhead. Without this, a long
// script holds every line's raw PCM in memory at once and crashes mobile Safari.
const REH_DECODE_WINDOW = 8;
function _rehEvictDecoded(keepIdx) {
  if (rehDecodedBuffers.size <= REH_DECODE_WINDOW * 2 + 4) return;
  const lo = keepIdx - REH_DECODE_WINDOW, hi = keepIdx + REH_DECODE_WINDOW;
  for (const k of rehDecodedBuffers.keys()) {
    if (k < lo || k > hi) rehDecodedBuffers.delete(k);
  }
}

async function preDecodeBlob(lineIdx, blob) {
  if (rehDecodedBuffers.has(lineIdx)) return;
  try {
    const ab  = await blob.arrayBuffer();
    const buf = await rehPlayCtx().decodeAudioData(ab);
    rehDecodedBuffers.set(lineIdx, buf);
    _rehEvictDecoded(lineIdx);
  } catch(_) {}
}

function computeWordTimings(text, durationSec) {
  const words = stripMarkdown(text).split(/\s+/).filter(Boolean);
  if (words.length < 2) return [];
  // Distribute proportionally by character length (longer words = more time)
  const totalChars = words.reduce((s, w) => s + w.length, 0) || 1;
  let t = 0;
  return words.map(w => {
    const start = t;
    t += (w.length / totalChars) * durationSec;
    return { word: w, start, end: t };
  });
}

function stopAudioSource() {
  if (rehCurrentSource) {
    try { rehCurrentSource.stop(0); } catch(_) {}
    rehCurrentSource = null;
  }
  if (rehWordHighlightRaf) { cancelAnimationFrame(rehWordHighlightRaf); rehWordHighlightRaf = null; }
}

// Instant playback from pre-decoded buffer + word-level highlight
async function playPreDecoded(lineIdx, blob, text) {
  if (!rehDecodedBuffers.has(lineIdx)) await preDecodeBlob(lineIdx, blob);
  _rehEvictDecoded(lineIdx);   // keep the window centred on the playhead
  const buf = rehDecodedBuffers.get(lineIdx);
  if (!buf) { await playAudioBlobFallback(blob); return; }

  const timings = computeWordTimings(text, buf.duration);
  const dialogEl = document.getElementById('reh-diag-' + lineIdx);

  if (dialogEl && timings.length >= 2) {
    dialogEl.innerHTML = timings.map((t, i) =>
      `<span class="reh-word" data-wi="${i}">${escHtml(t.word)}</span>`
    ).join(' ');
  }

  return new Promise(resolve => {
    stopAudioSource();
    const ctx = rehPlayCtx();
    const src = ctx.createBufferSource();
    src.buffer = buf;
    src.connect(ctx.destination);
    rehCurrentSource = src;
    const t0 = ctx.currentTime;

    src.onended = () => {
      rehCurrentSource = null;
      if (rehWordHighlightRaf) { cancelAnimationFrame(rehWordHighlightRaf); rehWordHighlightRaf = null; }
      if (dialogEl && timings.length >= 2) dialogEl.innerHTML = renderMarkdownInline(text);
      resolve();
    };

    src.start(0);

    // Pre-decode the line AFTER this one while this is playing
    const nextI = findNextCachedLine(lineIdx + 1);
    if (nextI >= 0) preDecodeBlob(nextI, rehState.synthCache.get(nextI));

    if (dialogEl && timings.length >= 2) {
      const tick = () => {
        if (rehCurrentSource !== src) return;
        const elapsed = ctx.currentTime - t0;
        let active = 0;
        for (let i = timings.length - 1; i >= 0; i--) {
          if (elapsed >= timings[i].start) { active = i; break; }
        }
        dialogEl.querySelectorAll('.reh-word').forEach((span, i) => {
          span.classList.toggle('reh-word-active', i === active);
        });
        rehWordHighlightRaf = requestAnimationFrame(tick);
      };
      rehWordHighlightRaf = requestAnimationFrame(tick);
    }
  });
}

function findNextCachedLine(fromIdx) {
  for (let i = fromIdx; i < rehState.lines.length; i++) {
    if (rehState.synthCache.has(i)) return i;
  }
  return -1;
}

// Fallback when AudioContext decode fails
async function playAudioBlobFallback(blob) {
  const url   = URL.createObjectURL(blob);
  const audio = $('reh-tts-audio'); if (!audio) return;
  audio.src = url; audio.style.display = '';
  await new Promise(r => { audio.addEventListener('canplay', r, { once: true }); setTimeout(r, 3000); });
  await audio.play().catch(() => {});
  await waitForAudioEnd(audio);
}

// ── Auto-play sequence ──────────────────────────────────────────────────────

function startPlay() {
  rehPlayCtx(); // warm up AudioContext on user gesture
  _ensureNarrator();  // make sure rehState.narratorVoice reflects the narrator cast row
  rehState.playing = true;
  updatePlayBtn();
  playNextLine();
}

// Resets the narrator play button's icon back to "play" — separate from
// highlightCurrentLine() (which also moves the active-line highlight and
// scrolls) since pausing/stopping shouldn't jump the page around, just
// stop claiming a line is still playing.
function _rehResetActionPlayIcons() {
  document.querySelectorAll('.reh-action-play-btn').forEach(btn => {
    const icon = btn.querySelector('.mdi');
    if (icon) icon.className = 'mdi mdi-play';
    btn.title = 'Play or pause this line';
  });
}

function pausePlay() {
  rehState.playing = false;
  updatePlayBtn();
  stopAudioSource();
  const audio = $('reh-tts-audio');
  if (audio && !audio.paused) audio.pause();
  hideStatusBar();
  _rehResetActionPlayIcons();
}

function stopPlay() {
  rehState.playing = false;
  updatePlayBtn();
  stopAudioSource();
  const audio = $('reh-tts-audio');
  if (audio) { audio.pause(); audio.src = ''; }
  hideStatusBar();
  _rehResetActionPlayIcons();
}

function hideStatusBar() { const bar = $('reh-tts-status-bar'); if (bar) bar.hidden = true; }

let _rehPrefetchRunning = false;
async function _rehPrefetchLines(fromIndex) {
  if (_rehPrefetchRunning) return;
  _rehPrefetchRunning = true;
  try {
    let prefetched = 0;
    for (let i = fromIndex; i < rehState.lines.length && prefetched < 2; i++) {
      if (!rehState.playing) break;
      const l = rehState.lines[i];
      if (!l || l.ignored || l.hidden || l.type === 'pagebreak') continue;
      
      const isDialog = l.type === 'dialog';
      const cast = isDialog ? (rehState.cast[l.speaker] || { voice: '' }) : null;
      if (isDialog && (!cast.voice || cast.voice === 'me')) continue;
      if (!isDialog && (!rehState.narratorVoice || !(l.text || '').trim() || rehState.skipDescriptions)) continue;
      
      if (rehState.synthCache.has(i) && !rehState.staleLines.has(i)) {
        prefetched++;
        continue;
      }
      
      const voice = isDialog ? cast.voice : rehState.narratorVoice;
      const cleanTxt = stripMarkdown(l.text);
      const instruct = isDialog ? _buildInstruct((cast.instruct || '').trim(), l.emotion, voice) : '';
      const text = isDialog ? _rehInlineTone(cleanTxt, l.emotion) : cleanTxt;
      
      const book = _lineAudioBookName();
      const cacheKey = await _lineAudioCacheKey(text, voice, instruct);
      let blob = await _lineAudioCacheGet(book, cacheKey);
      
      if (!blob) {
        try {
          blob = await fetchTtsPreviewBlob(voice, text, 'wav', instruct, _ttsBackendForVoice(voice, rehState.backend));
          _lineAudioCachePut(book, cacheKey, blob);
        } catch(e) {
          console.warn('Prefetch failed for line', i, e);
          continue; // skip counting as prefetched if it failed
        }
      }
      
      rehState.synthCache.set(i, blob);
      rehState.staleLines.delete(i);
      _markSynthDot(i, 'ok');
      prefetched++;
    }
  } finally {
    _rehPrefetchRunning = false;
  }
}
async function playNextLine() {
  if (!rehState.playing) return;

  // Check practice end boundary
  if (rehState.practiceEnd !== null && rehState.lineIndex > rehState.practiceEnd) {
    rehState.playing = false;
    updatePlayBtn();
    if (rehState.repeat) {
      rehState.lineIndex = rehState.practiceStart ?? 0;
      startPlay();
    } else {
      rehState.lineIndex = rehState.practiceStart ?? 0;
      highlightCurrentLine();
    }
    return;
  }

  // Always skip pagebreak markers
  if (rehState.lines[rehState.lineIndex]?.type === 'pagebreak') {
    rehState.lineIndex++;
    return playNextLine();
  }

  // Skip lines the user marked ignore / hide during bulk edit
  const _cur = rehState.lines[rehState.lineIndex];
  if (_cur && (_cur.ignored || _cur.hidden)) {
    rehState.lineIndex++;
    return playNextLine();
  }

  // Skip non-dialog lines whenever skip mode is on, full stop — regardless of
  // whether a narrator voice happens to be assigned. This used to also require
  // !rehState.narratorVoice, on the theory that skipping was only meaningful
  // when there was nothing to skip TO — but the individual-line branch below
  // never re-checked skipDescriptions at all, so once ANY narrator voice was
  // configured (the common case once a book is actually set up), narration
  // played regardless of this toggle. Confirmed live: Studio's "Rehearse ⇄
  // Audiobook" toggle (which just flips this same flag) had zero observable
  // effect once a narrator voice existed — exactly the reported "doesn't
  // read the narrator" / toggle-does-nothing behavior, just inverted from
  // what it looked like (narration was stuck ON, not stuck OFF).
  if (rehState.skipDescriptions) {
    while (
      rehState.lineIndex < rehState.lines.length &&
      rehState.lines[rehState.lineIndex].type !== 'dialog' &&
      rehState.lines[rehState.lineIndex].type !== 'pagebreak' &&
      !(rehState.practiceEnd !== null && rehState.lineIndex > rehState.practiceEnd)
    ) { rehState.lineIndex++; }
  }

  if (rehState.lineIndex >= rehState.lines.length) {
    rehState.playing = false;
    updatePlayBtn();
    if (rehState.repeat) { rehState.lineIndex = 0; startPlay(); return; }
    toast('Script finished', 'success');
    return;
  }

  // Captured up front so a later `await` (waiting on a fresh TTS synthesis)
  // can tell whether the user has since clicked a DIFFERENT line's play
  // button — `rehState.lineIndex` itself gets overwritten by that click, so
  // re-reading it after the await always looks "current" even when it
  // isn't. Checking only `rehState.playing` (a bare boolean, flipped false
  // then true again by the new click's own stopPlay()/startPlay() pair
  // before this await ever resumes) let this stale continuation slip
  // through and actually play — confirmed live as the reported bug: click
  // a line while a previous, not-yet-synthesized line is still loading, and
  // once that first synthesis finally finishes it cuts in and starts
  // playing anyway, on top of (or right over) the line the user actually
  // asked for, with no way to stop just that stray one.
  const myLineIndex = rehState.lineIndex;
  const stillCurrent = () => rehState.playing && rehState.lineIndex === myLineIndex;
  const line = rehState.lines[rehState.lineIndex];
  highlightCurrentLine();

  _rehPrefetchLines(myLineIndex + 1).catch(e => console.warn('Prefetch error:', e));

  // Non-dialog lines
  if (line.type !== 'dialog') {
    // Any line with text can be narrated — direction/transition/scene/act/action all included
    const hasText = !!(line.text || '').trim();
    if (rehState.narratorVoice && hasText && !rehState.skipDescriptions) {
      showStatusBar('Narrator: ' + line.text.slice(0, 50) + (line.text.length > 50 ? '…' : ''));
      const cached = rehState.synthCache.get(rehState.lineIndex);
      if (cached) {
        await playPreDecoded(rehState.lineIndex, cached, line.text);
      } else {
        try {
          const book = _lineAudioBookName();
          const cleanNarr = stripMarkdown(line.text);
          const cacheKey = await _lineAudioCacheKey(cleanNarr, rehState.narratorVoice, '');
          if (!stillCurrent()) return;
          let blob = await _lineAudioCacheGet(book, cacheKey);
          if (!stillCurrent()) return;
          if (!blob) {
            blob = await fetchTtsPreviewBlob(rehState.narratorVoice, cleanNarr, 'wav', '', _ttsBackendForVoice(rehState.narratorVoice, rehState.backend));
            if (!stillCurrent()) return;
            _lineAudioCachePut(book, cacheKey, blob);
          }
          rehState.synthCache.set(myLineIndex, blob);
          _markSynthDot(myLineIndex, 'ok');
          await playPreDecoded(myLineIndex, blob, line.text);
        } catch(_) { await new Promise(r => setTimeout(r, 200)); }
      }
    } else if (!rehState.skipDescriptions) {
      await new Promise(r => setTimeout(r, line.type === 'direction' ? 150 : 250));
    }
    if (!stillCurrent()) return;
    rehState.lineIndex++;
    playNextLine();
    return;
  }

  // Dialog line
  const cast = rehState.cast[line.speaker] || { voice: '' };

  if (cast.voice === 'me') {
    rehState.playing = false; updatePlayBtn();
    showRecOverlay(line);
    return;
  }

  if (!cast.voice) {
    showStatusBar(line.speaker + ' has no voice — skipping…');
    await new Promise(r => setTimeout(r, 350));
    if (!stillCurrent()) return;
    rehState.lineIndex++; playNextLine(); return;
  }

  const profile  = (cast.instruct || '').trim();
  const instruct = _buildInstruct(profile, line.emotion, cast.voice);
  const cleanTxt = stripMarkdown(line.text);

  const cached = rehState.synthCache.get(rehState.lineIndex);
  if (cached) {
    showStatusBar(line.speaker + ' is speaking…');
    await playPreDecoded(rehState.lineIndex, cached, line.text);  // ← instant: pre-decoded PCM
    rehState.clips.push({ lineIndex: rehState.lineIndex, speaker: line.speaker, type: 'tts', blob: cached });
  } else {
    showStatusBar('Synthesizing…');
    try {
      const toneText = _rehInlineTone(cleanTxt, line.emotion);
      const book = _lineAudioBookName();
      const cacheKey = await _lineAudioCacheKey(toneText, cast.voice, instruct);
      if (!stillCurrent()) return;
      let blob = await _lineAudioCacheGet(book, cacheKey);
      if (!stillCurrent()) return;
      if (!blob) {
        blob = await fetchTtsPreviewBlob(cast.voice, toneText, 'wav', instruct, _ttsBackendForVoice(cast.voice, rehState.backend));
        if (!stillCurrent()) return;
        _lineAudioCachePut(book, cacheKey, blob);
      }
      rehState.synthCache.set(myLineIndex, blob);
      showStatusBar(line.speaker + ' is speaking…');
      await playPreDecoded(myLineIndex, blob, line.text);  // also decodes + pre-fetches next
      rehState.clips.push({ lineIndex: myLineIndex, speaker: line.speaker, type: 'tts', blob });
    } catch(e) {
      showStatusBar('TTS failed: ' + e.message);
      await new Promise(r => setTimeout(r, 1000));
    }
  }

  if (!stillCurrent()) return;
  rehState.lineIndex++;
  playNextLine();
}

function waitForAudioEnd(audio) {
  return new Promise(resolve => {
    if (!audio || audio.paused || audio.ended) { resolve(); return; }
    audio.addEventListener('ended', resolve, { once: true });
    audio.addEventListener('pause',  resolve, { once: true });
    audio.addEventListener('error',  resolve, { once: true });
  });
}

function showStatusBar(msg) {
  const bar = $('reh-tts-status-bar'); if (!bar) return;
  bar.hidden = false;
  const txt = $('reh-tts-status-txt'); if (txt) txt.textContent = msg;
}

function highlightCurrentLine() {
  const i = rehState.lineIndex, total = rehState.lines.length;
  const prog = $('reh-tb-progress');
  if (prog) prog.style.width = (total ? (i / total) * 100 : 0) + '%';
  const lbl = $('reh-tb-label');
  if (lbl) lbl.textContent = `${i + 1} / ${total}`;

  document.querySelectorAll('[data-index]').forEach(el => {
    el.classList.toggle('reh-line-active', parseInt(el.dataset.index) === i);
  });

  // Dialogue's own play button shows play/pause via a pure-CSS badge
  // overlay on the avatar (.reh-line-active .reh-line-play-avatar::after),
  // but the plain narrator play button (.reh-action-play-btn, no avatar to
  // overlay onto) never got the same treatment — its icon just stayed a
  // static play triangle even while that exact line was the one actively
  // playing, with nothing to show that clicking it again would stop it.
  // Confirmed live as the reported "no way to stop it" complaint.
  document.querySelectorAll('.reh-action-play-btn').forEach(btn => {
    const icon = btn.querySelector('.mdi');
    if (!icon) return;
    const isActive = rehState.playing && parseInt(btn.dataset.index) === i;
    icon.className = isActive ? 'mdi mdi-stop' : 'mdi mdi-play';
    btn.title = isActive ? 'Stop' : 'Play or pause this line';
  });

  const active = document.querySelector(`[data-index="${i}"]`);
  if (active) active.scrollIntoView({ behavior: 'smooth', block: 'center' });
  updatePlayBtn();
}

function updatePlayBtn() {
  const btn = $('reh-tb-play'); if (!btn) return;
  btn.innerHTML = rehState.playing ? '<span class="mdi mdi-pause"></span>' : '<span class="mdi mdi-play"></span>';
  btn.title     = rehState.playing ? 'Pause' : 'Play all';
}

// ── Persistent per-paragraph audio cache ────────────────────────────────────
//
// rehState.synthCache only ever lived in the browser tab's memory — closing
// the tab, reloading, or a crash threw away everything "Synth all" had
// already paid GPU time for, forcing a full re-synthesis (and the pause
// between paragraphs that comes with it) the next time regardless. This
// persists each line's audio to disk, keyed by a hash of exactly what
// determines its sound (text + voice + tone/instruct) rather than its
// position in the script. An untouched paragraph's key never changes, so it
// keeps reusing the same cached file indefinitely; an edited paragraph's
// key changes the instant the text (or voice/tone) does, so it simply never
// matches a cached file again and gets synthesized fresh next time — no
// separate "delete the old file" step needed, the old file just becomes
// unreachable dead weight rather than ever being served again.
async function _lineAudioCacheKey(text, voice, instruct) {
  const enc = new TextEncoder().encode(`${text}\0${voice}\0${instruct || ''}`);
  const digest = await crypto.subtle.digest('SHA-256', enc);
  return [...new Uint8Array(digest)].map(b => b.toString(16).padStart(2, '0')).join('').slice(0, 32);
}
function _lineAudioBookName() {
  return $('reh-script-title')?.value.trim() || 'Untitled';
}
async function _lineAudioCacheGet(book, key) {
  try {
    const r = await fetch(`/api/line-audio/${encodeURIComponent(book)}/${key}`);
    if (!r.ok) return null;
    return await r.blob();
  } catch (_) { return null; }
}
function _lineAudioCachePut(book, key, blob) {
  // Fire-and-forget — a failed save just means this line resynthesizes next
  // time too, no worse than before this cache existed at all.
  fetch(`/api/line-audio/${encodeURIComponent(book)}/${key}`, { method: 'POST', body: blob }).catch(() => {});
}

// Every line's "pre-synthesized" green dot only ever reflected
// rehState.synthCache — this browser tab's own memory, empty on every fresh
// page load — so a script that was fully "Synth all"-ed and safely
// persisted to disk in an EARLIER session still looked completely
// unsynthesized after a reload, with no way to tell the cached audio was
// actually right there. This asks the server, in one batch request, which
// of the current script's lines already have a matching file, and lights
// up their dots — without downloading any actual audio (that still only
// happens lazily, right when a line is about to play).
let _lineAudioSyncedFor = null; // unused now, kept for compat
async function _lineAudioSyncDots() {
  const book = _lineAudioBookName();
  _ensureNarrator();
  const idxToKey = new Map();
  for (let i = 0; i < rehState.lines.length; i++) {
    const line = rehState.lines[i];
    if (line.ignored || line.hidden) continue;
    if (rehState.synthCache.has(i)) continue; // already known-good this session
    let voice, instruct, text;
    if (line.type === 'dialog') {
      const c = rehState.cast[line.speaker];
      if (!c || !c.voice || c.voice === 'me') continue;
      voice = c.voice;
      instruct = _buildInstruct(c.instruct, line.emotion, c.voice);
      text = _rehInlineTone(stripMarkdown(line.text), line.emotion);
    } else {
      if (!rehState.narratorVoice || !(line.text || '').trim()) continue;
      voice = rehState.narratorVoice; instruct = '';
      text = stripMarkdown(line.text);
    }
    idxToKey.set(i, await _lineAudioCacheKey(text, voice, instruct));
  }
  if (!idxToKey.size) return;
  const keyToIdx = new Map([...idxToKey].map(([i, k]) => [k, i]));
  try {
    const r = await fetch(`/api/line-audio/${encodeURIComponent(book)}/check`, {
      method: 'POST', headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ keys: [...idxToKey.values()] }),
    });
    if (!r.ok) return;
    const { existing } = await r.json();
    (existing || []).forEach(key => {
      const idx = keyToIdx.get(key);
      if (idx == null) return;
      rehState.staleLines.delete(idx);
      _markSynthDot(idx, 'ok');
    });
  } catch (_) { /* dots just stay as-is; playback still checks the disk cache lazily either way */ }
}

// ── Synthesize All ─────────────────────────────────────────────────────────

async function synthAll() {
  if (rehState.synthRunning) return;
  if (!rehState.backend) { toast('Select a TTS backend first', 'error'); return; }
  _ensureNarrator();  // sync narrator voice from its cast row before synthesizing

  const ttsLines = rehState.lines.map((l, i) => ({ line:l, idx:i })).filter(({ line }) => {
    if (line.ignored || line.hidden) return false;  // bulk-edit: never synth ignored/hidden lines
    if (line.type === 'dialog') {
      const c = rehState.cast[line.speaker];
      return c && c.voice && c.voice !== 'me';
    }
    // All non-dialog lines with text are narrated when a narrator voice is set
    return !!(rehState.narratorVoice && (line.text || '').trim());
  });

  if (!ttsLines.length) { toast('No TTS lines to synthesize', 'error'); return; }

  rehState.synthRunning = true; rehState.synthCancelled = false;
  const synthBar = $('reh-synth-bar'), fill = $('reh-synth-fill'), label = $('reh-synth-label');
  if (synthBar) synthBar.hidden = false;

  const prog = (d, t) => {
    if (fill)  fill.style.width   = (t ? (d/t)*100 : 0) + '%';
    if (label) label.textContent  = `${d} / ${t} synthesized`;
  };
  prog(0, ttsLines.length);

  let done = 0;
  const book = _lineAudioBookName();
  // Wrapped in try/finally so a thrown error (e.g. the speaker's cast entry
  // got deleted mid-run — see the `!c` guard below) can never leave
  // synthRunning stuck true forever, which would silently no-op every future
  // "Synthesize All" / "Re-synthesize stale" click with no error shown, same
  // failure shape as the character-sheets generation-lock bug fixed earlier.
  try {
    for (const { line, idx } of ttsLines) {
      if (rehState.synthCancelled) break;
      let voice, instruct;
      if (line.type === 'dialog') {
        const c = rehState.cast[line.speaker];
        if (!c || !c.voice || c.voice === 'me') { _markSynthDot(idx, null); prog(++done, ttsLines.length); continue; }
        voice    = c.voice;
        instruct = _buildInstruct(c.instruct, line.emotion, c.voice);
      } else {
        voice = rehState.narratorVoice; instruct = '';
      }
      _markSynthDot(idx, 'synthesizing');
      document.getElementById('reh-syd-' + idx)?.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
      const toneText = _rehInlineTone(stripMarkdown(line.text), line.emotion);
      try {
        const cacheKey = await _lineAudioCacheKey(toneText, voice, instruct);
        let blob = await _lineAudioCacheGet(book, cacheKey);
        if (!blob) {
          blob = await fetchTtsPreviewBlob(voice, toneText, 'wav', instruct, _ttsBackendForVoice(voice, rehState.backend));
          _lineAudioCachePut(book, cacheKey, blob);
        }
        rehState.synthCache.set(idx, blob);
        rehState.staleLines.delete(idx);
        _markSynthDot(idx, 'ok');
        _showReSynthBtn(idx, false);
        preDecodeBlob(idx, blob);  // decode to PCM immediately → zero-latency playback
      } catch(_) { _markSynthDot(idx, null); }
      prog(++done, ttsLines.length);
    }
  } finally {
    if (synthBar) synthBar.hidden = true;
    rehState.synthRunning = false;
  }
  if (!rehState.synthCancelled) toast(`Pre-synthesized ${done} of ${ttsLines.length} lines — ready for instant playback`, 'success');
}

function _updateStaleBatchBtn() {
  const btn = $('reh-tb-resynth-stale');
  if (btn) btn.hidden = rehState.staleLines.size === 0;
}

$('reh-tb-synth-all')?.addEventListener('click', () => synthAll());
$('reh-tb-resynth-stale')?.addEventListener('click', async () => {
  if (rehState.synthRunning) return;
  const stale = [...rehState.staleLines];
  if (!stale.length) return;
  rehState.synthRunning = true; rehState.synthCancelled = false;
  const synthBar = $('reh-synth-bar'), fill = $('reh-synth-fill'), label = $('reh-synth-label');
  if (synthBar) synthBar.hidden = false;
  let done = 0;
  const book = _lineAudioBookName();
  try {
    for (const idx of stale) {
      if (rehState.synthCancelled) break;
      const line = rehState.lines[idx];
      if (!line || line.type !== 'dialog') { rehState.staleLines.delete(idx); continue; }
      const c = rehState.cast[line.speaker];
      if (!c || !c.voice || c.voice === 'me') { rehState.staleLines.delete(idx); continue; }
      const instruct = [c.instruct||'', line.emotion||''].filter(Boolean).join('. ');
      _markSynthDot(idx, 'synthesizing');
      const toneText = _rehInlineTone(stripMarkdown(line.text), line.emotion);
      try {
        const cacheKey = await _lineAudioCacheKey(toneText, c.voice, instruct);
        let blob = await _lineAudioCacheGet(book, cacheKey);
        if (!blob) {
          blob = await fetchTtsPreviewBlob(c.voice, toneText, 'wav', instruct, _ttsBackendForVoice(c.voice, rehState.backend));
          _lineAudioCachePut(book, cacheKey, blob);
        }
        rehState.synthCache.set(idx, blob);
        rehState.staleLines.delete(idx);
        preDecodeBlob(idx, blob);
        _markSynthDot(idx, 'ok');
        _showReSynthBtn(idx, false);
      } catch(_) { _markSynthDot(idx, 'stale'); }
      if (fill)  fill.style.width  = ((++done / stale.length) * 100) + '%';
      if (label) label.textContent = `${done} / ${stale.length} synthesized`;
    }
  } finally {
    if (synthBar) synthBar.hidden = true;
    rehState.synthRunning = false;
    _updateStaleBatchBtn();
  }
  if (!rehState.synthCancelled) toast(`Re-synthesized ${done} stale line${done !== 1 ? 's' : ''}`, 'success');
});
$('reh-synth-cancel')?.addEventListener('click', () => { rehState.synthCancelled = true; rehState.synthRunning = false; });

// Editing a paragraph doesn't delete its OLD cached audio file — the write
// path only ever knows the NEW content's hash, not whatever the line used
// to hash to before the edit, so the stale file just sits there unreferenced
// forever. This computes every key the CURRENT script would actually use
// and asks the server to delete anything else on disk for this book.
$('reh-tb-clean-cache')?.addEventListener('click', async () => {
  const btn = $('reh-tb-clean-cache');
  if (btn) { btn.disabled = true; btn.innerHTML = '<span class="mdi mdi-loading mdi-spin"></span> Scanning…'; }
  try {
    _ensureNarrator();
    const keep = [];
    for (const line of rehState.lines) {
      if (line.ignored || line.hidden) continue;
      let voice, instruct, text;
      if (line.type === 'dialog') {
        const c = rehState.cast[line.speaker];
        if (!c || !c.voice || c.voice === 'me') continue;
        voice = c.voice;
        instruct = _buildInstruct(c.instruct, line.emotion, c.voice);
        text = _rehInlineTone(stripMarkdown(line.text), line.emotion);
      } else {
        if (!rehState.narratorVoice || !(line.text || '').trim()) continue;
        voice = rehState.narratorVoice; instruct = '';
        text = stripMarkdown(line.text);
      }
      keep.push(await _lineAudioCacheKey(text, voice, instruct));
    }
    const book = _lineAudioBookName();
    const r = await fetch(`/api/line-audio/${encodeURIComponent(book)}/prune`, {
      method: 'POST', headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ keep }),
    });
    if (!r.ok) throw new Error((await r.json().catch(() => ({}))).detail || r.statusText);
    const d = await r.json();
    toast(d.deleted ? `Cleaned up ${d.deleted} unused cached audio file${d.deleted !== 1 ? 's' : ''}` : 'Nothing to clean up — every cached file is still in use', 'success');
  } catch (e) {
    toast('Cache cleanup failed: ' + (e.message || e), 'error');
  } finally {
    if (btn) { btn.disabled = false; btn.innerHTML = '<span class="mdi mdi-broom"></span> Clean cache'; }
  }
});


window.TTVC = window.TTVC || {};
window.TTVC.rehearser = window.TTVC.rehearser || {};
Object.assign(window.TTVC.rehearser, {
  playback: {
    start: startPlay,
    pause: pausePlay,
    stop: stopPlay,
    playNext: playNextLine,
    synthAll,
    syncCacheDots: _lineAudioSyncDots,
  },
});