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

/**
 * The Music app's persistent player bar (docs/musicbay.md §2.3, §7.2).
 *
 * Owned and rendered by group-page.js, *not* by music-app.js: it is the one
 * piece of this feature that lives outside the tab-switched area, so
 * playback survives navigating to Chat or Files, exactly the way the
 * video/preview modals are shell-owned rather than owned by whichever app
 * opened them. music-app.js never touches audio state directly — it only
 * calls `onPlayQueue(tracks, startIndex)`, threaded down from group-page.js,
 * to hand this component a new queue.
 *
 * No streaming, no MSE, no node-side transcode pool for the common case: a
 * track is a few megabytes, so it is downloaded and decrypted once through
 * the same chunk pipeline Files already uses (file-utils.js's
 * pipelinedDownload), then played from a blob URL — the deliberate
 * simplification recorded in musicbay.md §2.2. WMA and Musepack are the one
 * exception (`NEEDS_TRANSCODE_RE` below): neither decodes in a browser's
 * <audio> element at all, tagged correctly or not, so those two go through
 * `transport.requestAudioTranscode` first — a node-side, cached-after-once
 * AAC/M4A conversion — before the same download/blob path runs.
 */

const MIME_BY_EXT = {
  mp3: 'audio/mpeg', flac: 'audio/flac', ogg: 'audio/ogg', opus: 'audio/opus',
  wav: 'audio/wav', aac: 'audio/aac', m4a: 'audio/mp4',
};

// Kept in sync with the node's BROWSER_INCOMPATIBLE_AUDIO_EXTS
// (webrtc_server.py) — both name the same two formats no mainstream
// browser's <audio> element decodes natively.
const NEEDS_TRANSCODE_RE = /\.(wma|mpc)$/i;

function guessMime(name) {
  const ext = (name || '').split('.').pop().toLowerCase();
  return MIME_BY_EXT[ext] || 'audio/mpeg';
}

function formatTime(seconds) {
  if (!isFinite(seconds) || seconds < 0) return '0:00';
  const total = Math.floor(seconds);
  const m = Math.floor(total / 60);
  const s = total % 60;
  return `${m}:${String(s).padStart(2, '0')}`;
}

function shuffledOrder(n, keepFirst) {
  const order = Array.from({ length: n }, (_, i) => i);
  // Fisher-Yates, then move keepFirst to the front so shuffling on doesn't
  // interrupt whatever is already playing.
  for (let i = order.length - 1; i > 0; i--) {
    const j = Math.floor(Math.random() * (i + 1));
    [order[i], order[j]] = [order[j], order[i]];
  }
  if (keepFirst != null) {
    const at = order.indexOf(keepFirst);
    if (at > 0) { order.splice(at, 1); order.unshift(keepFirst); }
  }
  return order;
}

// Bounded: only the currently playing track plus a one-track read-ahead are
// ever worth holding in memory. Older blob URLs are revoked, not merely
// dropped — otherwise every track played in a session leaks its object URL.
const MAX_CACHED_BLOBS = 3;

function loadVolume() {
  try {
    const v = parseFloat(localStorage.getItem('meshbay_music_volume'));
    return isFinite(v) && v >= 0 && v <= 1 ? v : 1;
  } catch { return 1; }
}
function saveVolume(v) {
  try { localStorage.setItem('meshbay_music_volume', String(v)); } catch { /* per-device only */ }
}
function loadShuffle() {
  try { return localStorage.getItem('meshbay_music_shuffle') === '1'; } catch { return false; }
}
function saveShuffle(v) {
  try { localStorage.setItem('meshbay_music_shuffle', v ? '1' : '0'); } catch { /* per-device only */ }
}
function loadRepeat() {
  try {
    const v = localStorage.getItem('meshbay_music_repeat');
    return v === 'all' || v === 'one' ? v : 'off';
  } catch { return 'off'; }
}
function saveRepeat(v) {
  try { localStorage.setItem('meshbay_music_repeat', v); } catch { /* per-device only */ }
}

// The current queue, tracklist form -- "go back to what's playing" without
// switching tabs or hunting for the album/folder it came from. Works the
// same regardless of how the queue was built (an album, a consolidated
// misc/loose bucket, a single standalone track).
//
// The header alone ("Playing now") named the *panel*, not the track — on a
// long queue the highlighted row can be scrolled out of view entirely, so
// opening this told you nothing you didn't already know. It now shows the
// current track's own title/artist right under the header, and scrolls the
// highlighted row into view on open rather than leaving it to be found.
function QueuePanel({ tracks, order, pos, onSelect, onClose }) {
  const activeRowRef = useRef(null);
  useEffect(() => {
    if (activeRowRef.current) {
      activeRowRef.current.scrollIntoView({ block: 'center' });
    }
  }, []);

  const current = tracks[order[pos]];

  return html`
    <div class="video-overlay" onClick=${(e) => {
      if (e.target.classList.contains('video-overlay')) onClose();
    }}>
      <div class="music-detail">
        <div class="video-top-bar">
          <span class="video-title">${t('music.queue_title')}</span>
          <button class="video-close" onClick=${onClose} title=${t('video.close')}>
            <${Icon} name="close" /></button>
        </div>
        ${current && html`
          <div class="music-queue-now-playing">
            <span class="music-queue-now-playing-title">
              ${current.display_title || current.name}</span>
            ${current.artist && html`
              <span class="music-queue-now-playing-artist"> — ${current.artist}</span>`}
          </div>
        `}
        <div class="music-detail-body">
          <div class="music-tracklist">
            ${order.map((idx, i) => html`
              <button class="music-track-row ${i === pos ? 'active' : ''}" key=${tracks[idx].id}
                ref=${i === pos ? activeRowRef : null}
                onClick=${() => { onSelect(i); onClose(); }}>
                <span class="music-track-no">${i + 1}</span>
                <span class="music-track-title">${tracks[idx].display_title || tracks[idx].name}</span>
                <span class="music-track-duration">${formatTime(tracks[idx].duration || 0)}</span>
              </button>
            `)}
          </div>
        </div>
      </div>
    </div>
  `;
}

function MusicPlayerBar({ transportRef, gekRef, queue, onClose }) {
  const audioRef = useRef(null);
  const blobCacheRef = useRef(new Map()); // file id -> { url, order: insertion index }
  const blobInsertRef = useRef(0);
  const loadTokenRef = useRef(0);

  const [tracks, setTracks] = useState([]);
  const [order, setOrder] = useState([]);
  const [pos, setPos] = useState(0); // index into `order`
  const [playing, setPlaying] = useState(false);
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState('');
  const [shuffle, setShuffle] = useState(loadShuffle);
  const [repeat, setRepeat] = useState(loadRepeat); // 'off' | 'all' | 'one'
  const [volume, setVolume] = useState(loadVolume);
  const [currentTime, setCurrentTime] = useState(0);
  const [duration, setDuration] = useState(0);
  const [showQueue, setShowQueue] = useState(false);
  // A broken source file (truncated download, a format the browser has no
  // decoder for) must not stall a "play all" queue on the one track that
  // failed — found live against a real library: a corrupt few-hundred-byte
  // file with no audio stream at all, sitting between two good tracks.
  // Bounded so a queue that turns out to be *entirely* bad (every file the
  // same unsupported format) fails once, visibly, rather than burning
  // through the whole list in an instant.
  const consecutiveFailuresRef = useRef(0);
  const MAX_CONSECUTIVE_FAILURES = 5;

  const currentTrack = tracks[order[pos]] || null;

  const advancePastFailure = useCallback(() => {
    consecutiveFailuresRef.current += 1;
    if (consecutiveFailuresRef.current > MAX_CONSECUTIVE_FAILURES || order.length <= 1) return;
    if (pos + 1 < order.length) setPos(pos + 1);
    else if (repeat === 'all') setPos(0);
  }, [order.length, pos, repeat]);

  // Stops playback the moment this bar goes away for any reason -- the
  // close button below, or the shell tearing it down on its own (leaving
  // the group, switching to a different one). A component removed from the
  // DOM should already stop an <audio> element, but that's the browser's
  // behaviour to rely on, not this app's to assert; pausing explicitly, and
  // releasing every cached blob URL rather than leaving them for the tab's
  // lifetime, costs nothing and isn't optional either way.
  useEffect(() => () => {
    const audio = audioRef.current;
    if (audio) { audio.pause(); audio.src = ''; }
    for (const { url } of blobCacheRef.current.values()) URL.revokeObjectURL(url);
  }, []);

  const evictOldBlobs = useCallback(() => {
    const cache = blobCacheRef.current;
    while (cache.size > MAX_CACHED_BLOBS) {
      let oldestId = null, oldestOrder = Infinity;
      for (const [id, v] of cache) {
        if (v.order < oldestOrder) { oldestOrder = v.order; oldestId = id; }
      }
      if (oldestId == null) break;
      URL.revokeObjectURL(cache.get(oldestId).url);
      cache.delete(oldestId);
    }
  }, []);

  const fetchTrackBlob = useCallback(async (entry) => {
    const cached = blobCacheRef.current.get(entry.id);
    if (cached) return cached.url;
    const transport = transportRef.current;
    if (!transport || !transport.connected) throw new Error(t('music.err_transport'));

    let downloadId = entry.id;
    let downloadSize = entry.size;
    let mime = guessMime(entry.name);
    if (NEEDS_TRANSCODE_RE.test(entry.name)) {
      let info;
      try {
        info = await transport.requestAudioTranscode(entry.id);
      } catch (err) {
        throw new Error(t('music.err_transcode'));
      }
      downloadId = info.hash;
      downloadSize = info.size;
      mime = info.mime || 'audio/mp4';
    }

    const totalChunks = Math.ceil(downloadSize / CHUNK_SIZE);
    const chunks = await pipelinedDownload(transport, gekRef.current, downloadId, totalChunks);
    const blob = new Blob(chunks, { type: mime });
    const url = URL.createObjectURL(blob);
    // Keyed by the track's own id, not `downloadId` — the transcode cache
    // hash is an implementation detail of getting there, and a second play
    // of the same track must still hit this cache rather than re-requesting
    // a transcode the node already ran once.
    blobCacheRef.current.set(entry.id, { url, order: blobInsertRef.current++ });
    evictOldBlobs();
    return url;
  }, [transportRef, gekRef, evictOldBlobs]);

  // Silently warms the cache for the next track so pressing "next" doesn't
  // visibly wait (musicbay.md §2.2) — best-effort, never surfaces an error.
  const prefetchNext = useCallback((fromPos) => {
    const nextEntry = tracks[order[fromPos + 1]];
    if (!nextEntry || blobCacheRef.current.has(nextEntry.id)) return;
    fetchTrackBlob(nextEntry).catch(() => {});
  }, [tracks, order, fetchTrackBlob]);

  // (Re)initialize the queue whenever the shell hands over a new one.
  // `queue.nonce` changes on every call to onPlayQueue, including "play the
  // same album again from track 0" — a fresh Date.now() each time, so this
  // effect always re-runs rather than bailing out on reference equality.
  useEffect(() => {
    if (!queue) return;
    const n = queue.tracks.length;
    const initialOrder = shuffle ? shuffledOrder(n, queue.startIndex) : Array.from({ length: n }, (_, i) => i);
    const startPos = shuffle ? 0 : queue.startIndex;
    setTracks(queue.tracks);
    setOrder(initialOrder);
    setPos(startPos);
    setError('');
    consecutiveFailuresRef.current = 0;
    // Playback itself starts from the effect below, keyed on [tracks, order, pos].
  }, [queue]);

  // Loads and plays whatever `pos` now points to. Runs after the queue
  // effect above (pos/order/tracks all just changed together) and also
  // after skipNext/skipPrev/onEnded update `pos` alone.
  useEffect(() => {
    if (!currentTrack) return;
    const myToken = ++loadTokenRef.current;
    setLoading(true);
    setError('');
    (async () => {
      try {
        const url = await fetchTrackBlob(currentTrack);
        if (loadTokenRef.current !== myToken) return; // superseded by a newer skip
        const audio = audioRef.current;
        if (!audio) return;
        audio.src = url;
        audio.currentTime = 0;
        await audio.play();
        consecutiveFailuresRef.current = 0;
        setPlaying(true);
        prefetchNext(pos);
      } catch (err) {
        if (loadTokenRef.current !== myToken) return;
        setError(err.message || String(err));
        setPlaying(false);
        advancePastFailure();
      } finally {
        if (loadTokenRef.current === myToken) setLoading(false);
      }
    })();
    // eslint-disable-next-line
  }, [currentTrack && currentTrack.id]);

  // Belt and suspenders alongside the catch block above: `.play()` rejecting
  // is the common path for a source the browser can't decode at all, but a
  // decode failure can also surface later, asynchronously, as an `error`
  // event on the element itself rather than a rejected promise — found live
  // to matter (a truncated file with a valid-looking header but no audio
  // stream). Both paths converge on the same bounded advance, so whichever
  // fires first, the queue moves on exactly once.
  const handleMediaError = useCallback(() => {
    const audio = audioRef.current;
    const mediaError = audio && audio.error;
    setError((mediaError && mediaError.message) || t('music.err_playback'));
    setPlaying(false);
    advancePastFailure();
  }, [advancePastFailure]);

  useEffect(() => {
    const audio = audioRef.current;
    if (audio) audio.volume = volume;
    saveVolume(volume);
  }, [volume]);

  const skipTo = useCallback((newPos) => setPos(newPos), []);

  const skipNext = useCallback(() => {
    if (order.length === 0) return;
    if (pos + 1 < order.length) { skipTo(pos + 1); return; }
    if (repeat === 'all') { skipTo(0); return; }
    setPlaying(false); // end of queue, nothing to repeat
  }, [pos, order.length, repeat, skipTo]);

  const skipPrev = useCallback(() => {
    if (order.length === 0) return;
    // A few seconds in: restart the current track, the way most players do,
    // rather than always jumping to the previous one.
    const audio = audioRef.current;
    if (audio && audio.currentTime > 3) { audio.currentTime = 0; return; }
    if (pos > 0) { skipTo(pos - 1); return; }
    if (repeat === 'all') { skipTo(order.length - 1); }
  }, [pos, order.length, repeat, skipTo]);

  const onEnded = useCallback(() => {
    if (repeat === 'one') {
      const audio = audioRef.current;
      if (audio) { audio.currentTime = 0; audio.play().catch(() => {}); }
      return;
    }
    skipNext();
  }, [repeat, skipNext]);

  const togglePlaying = useCallback(() => {
    const audio = audioRef.current;
    if (!audio) return;
    if (playing) { audio.pause(); setPlaying(false); }
    else { audio.play().then(() => setPlaying(true)).catch(() => {}); }
  }, [playing]);

  const toggleShuffle = useCallback(() => {
    setShuffle((prev) => {
      const next = !prev;
      saveShuffle(next);
      // Reshuffling keeps the currently playing track in place — turning
      // shuffle on mid-album must not interrupt what's already playing.
      const currentId = tracks[order[pos]] && tracks[order[pos]].id;
      const currentIdx = tracks.findIndex((tr) => tr.id === currentId);
      const newOrder = next
        ? shuffledOrder(tracks.length, currentIdx)
        : Array.from({ length: tracks.length }, (_, i) => i);
      setOrder(newOrder);
      setPos(next ? 0 : currentIdx);
      return next;
    });
  }, [tracks, order, pos]);

  const cycleRepeat = useCallback(() => {
    setRepeat((prev) => {
      const next = prev === 'off' ? 'all' : prev === 'all' ? 'one' : 'off';
      saveRepeat(next);
      return next;
    });
  }, []);

  const seek = useCallback((e) => {
    const audio = audioRef.current;
    if (audio && isFinite(audio.duration)) audio.currentTime = parseFloat(e.target.value);
  }, []);

  const handleClose = useCallback(() => {
    const audio = audioRef.current;
    if (audio) audio.pause();
    if (onClose) onClose();
  }, [onClose]);

  if (!currentTrack) return null;

  const title = currentTrack.display_title || currentTrack.name;
  const repeatLabel = repeat === 'off' ? t('music.player_repeat_off')
    : repeat === 'all' ? t('music.player_repeat_all') : t('music.player_repeat_one');

  return html`
    <div class="music-player-bar">
      <audio ref=${audioRef}
        onTimeUpdate=${(e) => setCurrentTime(e.target.currentTime)}
        onDurationChange=${(e) => setDuration(e.target.duration)}
        onEnded=${onEnded} onError=${handleMediaError} />
      <div class="music-player-info">
        <${Icon} name="music" cls="music-player-icon" />
        <div class="music-player-text">
          <div class="music-player-title">${title}</div>
          <div class="music-player-sub">
            ${[currentTrack.artist, currentTrack.album].filter(Boolean).join(' · ')}
          </div>
        </div>
      </div>
      <div class="music-player-transport">
        <button class="music-player-btn ${shuffle ? 'active' : ''}"
          title=${t('music.player_shuffle')} onClick=${toggleShuffle}>
          <${Icon} name="shuffle" />
        </button>
        <button class="music-player-btn" title=${t('music.player_prev')} onClick=${skipPrev}>
          <${Icon} name="skip-prev" />
        </button>
        <button class="music-player-btn music-player-play" title=${playing ? t('music.player_pause') : t('music.player_play')}
          onClick=${togglePlaying} disabled=${loading}>
          ${loading ? html`<span class="spinner"></span>` : html`<${Icon} name=${playing ? 'pause' : 'play'} />`}
        </button>
        <button class="music-player-btn" title=${t('music.player_next')} onClick=${skipNext}>
          <${Icon} name="skip-next" />
        </button>
        <button class="music-player-btn ${repeat !== 'off' ? 'active' : ''} music-player-repeat-${repeat}"
          title=${repeatLabel} onClick=${cycleRepeat}>
          <${Icon} name="repeat" />
          ${repeat === 'one' && html`<span class="music-repeat-badge">1</span>`}
        </button>
      </div>
      <div class="music-player-seek">
        <span class="music-player-time">${formatTime(currentTime)}</span>
        <input type="range" min="0" max=${duration || 0} step="1" value=${currentTime}
          disabled=${!duration} onInput=${seek} />
        <span class="music-player-time">${formatTime(duration)}</span>
      </div>
      <div class="music-player-volume">
        <${Icon} name="volume" />
        <input type="range" min="0" max="1" step="0.05" value=${volume}
          title=${t('music.player_volume')}
          onInput=${(e) => setVolume(parseFloat(e.target.value))} />
      </div>
      <div class="music-player-extra">
        <button class="music-player-btn" title=${t('music.player_queue')} onClick=${() => setShowQueue(true)}>
          <${Icon} name="menu" />
        </button>
        <button class="music-player-btn" title=${t('music.player_close')} onClick=${handleClose}>
          <${Icon} name="close" />
        </button>
      </div>
      ${error && html`<div class="music-player-error">${error}</div>`}
    </div>
    ${showQueue && html`
      <${QueuePanel} tracks=${tracks} order=${order} pos=${pos}
        onSelect=${skipTo} onClose=${() => setShowQueue(false)} />
    `}
  `;
}

export { MusicPlayerBar, formatTime };