import NetInfo from '@react-native-community/netinfo';
import {
  EventBuffer,
  WaveCoordinator,
  EARLY_SKIP_MS,
  type WaveInfo,
  type WaveOutcome,
  type WaveFeedback,
  PlayAttempt,
  normalizeGain,
  unwrap,
  type AuthSession,
  type PlayContext,
  type Track,
} from '@pipu/core';
import TrackPlayer, {
  AppKilledPlaybackBehavior,
  Capability,
  Event,
  State,
  type Track as RntpTrack,
} from 'react-native-track-player';

import { playerCache, qualityPrefs, type Quality } from '../lib/prefs';
import { downloads, sizedCover } from '../offline/downloads';
import { PersistentEvents } from '../offline/events';
import { offlineWave } from './offlineWave';
import { eventId } from './eventId';

export { offlineWave };

export type { WaveInfo } from '@pipu/core';

export interface PlayerState {
  ready: boolean;
  track: Track | null;
  queue: Track[];
  index: number;
  playing: boolean;
  buffering: boolean;
  positionMs: number;
  durationMs: number;
  context: PlayContext | null;
  wave: WaveInfo | null;
}

const SAVE_EVERY_MS = 10_000;

const playable = (t: Track) => t.available && (!!t.stream_url || downloads.isDownloaded(t.id));

/** Ссылки API относительные — для приложения нужен полный адрес сервера. */
export function absolute(server: string, path: string | null | undefined): string | undefined {
  if (!path) return undefined;
  return /^https?:/.test(path) ? path : server + path;
}

/** Качество по сети (docs/playback.md#качество): Wi-Fi — high, сотовая — medium. */
/** Качество стрима по типу сети — из настроек профиля. */
async function quality(): Promise<Quality> {
  const prefs = await qualityPrefs.load();
  try {
    const net = await NetInfo.fetch();
    return net.type === 'cellular' ? prefs.cellular : prefs.wifi;
  } catch {
    return prefs.wifi;
  }
}

/**
 * Плеер Android. Очередь живёт в ExoPlayer (react-native-track-player) — играет и с выгруженным UI;
 * здесь — зеркало очереди с DTO треков, учёт прослушиваний (PlayAttempt из @pipu/core), события,
 * реакции и бесконечная волна. Один экземпляр на процесс: им пользуются и экраны, и фоновый сервис.
 */
class Controller {
  private session: AuthSession | null = null;
  private server = '';
  private events: EventBuffer | null = null;
  private persistent: PersistentEvents | null = null;
  private unsubscribeNet: (() => void) | null = null;
  private attempt: PlayAttempt | null = null;
  private lastPositionMs = 0;
  private lastSave = 0;
  private readonly wavePolicy = new WaveCoordinator({
    next: async (id: string, feedback: WaveFeedback[]) => unwrap(
      await this.session!.client.POST('/api/v1/wave/sessions/{id}/next', {
        params: { path: { id } }, body: { feedback },
      }),
    ),
  });
  private neutralSwitch = false; // следующая смена трека — из-за нового контекста волны
  private setupDone: Promise<void> | null = null;
  private listeners = new Set<() => void>();
  private state: PlayerState = {
    ready: false, track: null, queue: [], index: 0, playing: false, buffering: false, positionMs: 0, durationMs: 0,
    context: null, wave: null,
  };

  subscribe = (fn: () => void) => {
    this.listeners.add(fn);
    return () => this.listeners.delete(fn);
  };

  getState = () => this.state;

  private update(patch: Partial<PlayerState>) {
    this.state = { ...this.state, ...patch };
    for (const fn of this.listeners) fn();
  }

  /** Привязка к вошедшему пользователю: события и реакции уходят на его сервер, без сети — копятся в SQLite. */
  attach(session: AuthSession | null, server: string, userId: string | null) {
    if (this.session === session) return;
    void this.events?.flush();
    this.session = session;
    this.server = server;
    this.persistent = session && userId ? new PersistentEvents(session, server, userId) : null;
    const sink = this.persistent;
    this.events = sink ? new EventBuffer({ send: sink.send }, Date.now, undefined, eventId) : null;
    void sink?.drain();
    this.unsubscribeNet ??= NetInfo.addEventListener((st) => {
      if (st.isConnected) void this.persistent?.drain();
    });
    if (!session) void this.reset();
  }

  setup(): Promise<void> {
    this.setupDone ??= (async () => {
      // Очистка кэша из профиля — только пока сервис плеера не запущен (иначе SimpleCache держит файлы).
      if (!(await TrackPlayer.isServiceRunning().catch(() => true))) await playerCache.clearIfRequested();
      try {
        // 500 МБ кэша ExoPlayer для недавних стримов (значение — в КБ).
        await TrackPlayer.setupPlayer({ maxCacheSize: 500 * 1024, autoHandleInterruptions: true });
      } catch {
        // уже настроен (повторный запуск JS при живом сервисе)
      }
      await TrackPlayer.updateOptions({
        capabilities: [Capability.Play, Capability.Pause, Capability.SkipToNext, Capability.SkipToPrevious, Capability.SeekTo],
        compactCapabilities: [Capability.Play, Capability.Pause, Capability.SkipToNext],
        progressUpdateEventInterval: 1,
        android: { appKilledPlaybackBehavior: AppKilledPlaybackBehavior.StopPlaybackAndRemoveNotification },
      });
      this.bind();
      this.update({ ready: true });
    })();
    return this.setupDone;
  }

  private bind() {
    TrackPlayer.addEventListener(Event.PlaybackState, ({ state }) => {
      this.update({ playing: state === State.Playing, buffering: state === State.Buffering || state === State.Loading });
      if (state === State.Paused) this.save();
    });
    TrackPlayer.addEventListener(Event.PlaybackProgressUpdated, ({ position, duration }) => {
      const ms = Math.round(position * 1000);
      this.attempt?.tick(ms);
      this.lastPositionMs = ms;
      this.update({ positionMs: ms, durationMs: Math.round(duration * 1000) || this.state.durationMs });
      if (this.state.playing && Date.now() - this.lastSave > SAVE_EVERY_MS) this.save();
      const cf = Math.min(6, Math.max(0, this.userPrefs()?.crossfade_s ?? 0));
      const left = duration - position;
      const fade = cf > 0 && left < cf ? Math.max(0, left / cf) : 1;
      void this.applyVolume(this.state.track, fade);
    });
    TrackPlayer.addEventListener(Event.PlaybackActiveTrackChanged, ({ index, lastPosition }) => {
      this.finishAttempt(lastPosition);
      if (index === undefined || index === null) return;
      const track = this.state.queue[index];
      if (!track) return;
      this.attempt = new PlayAttempt(track, 0);
      this.update({ track, index, positionMs: 0, durationMs: track.duration_ms });
      void this.applyVolume(track, 1);
      this.events?.push({
        type: 'play_start', track_id: track.id, position_ms: 0, context_type: this.state.context?.type,
        context_id: this.state.context?.id,
      });
      this.save();
      void this.refillWave();
    });
    TrackPlayer.addEventListener(Event.PlaybackQueueEnded, () => {
      this.finishAttempt(this.lastPositionMs / 1000, true);
      void this.events?.flush();
    });
    TrackPlayer.addEventListener(Event.PlaybackError, () => {
      // Ссылка могла устареть или трек пропал — переходим дальше, ExoPlayer не застрянет на ошибке.
      void TrackPlayer.skipToNext().catch(() => undefined);
    });
  }

  /** Завершение попытки: доиграно (позиция у конца) или пропущено. */
  private finishAttempt(lastPositionS: number, ended = false) {
    const a = this.attempt;
    if (!a) return;
    this.attempt = null;
    const pos = Math.round(lastPositionS * 1000);
    if (this.neutralSwitch) {
      this.neutralSwitch = false;
      if (a.playedMs >= EARLY_SKIP_MS) {
        this.events?.push({ type: 'skip', track_id: a.track.id, position_ms: pos, played_ms: Math.round(a.playedMs) });
        void this.events?.flush();
      }
      return;
    }
    const kind = ended ? 'play_end' : a.outcome(pos);
    this.events?.push({ type: kind, track_id: a.track.id, position_ms: pos, played_ms: Math.round(a.playedMs) });
    void this.events?.flush();
    if (kind === 'play_end') this.noteWave(a.track.id, 'complete');
    else {
      const early = a.playedMs < EARLY_SKIP_MS;
      this.noteWave(a.track.id, early ? 'skip_early' : 'skip');
      if (early) void this.refillWave(true);
    }
  }

  private userPrefs() {
    const st = this.session?.state;
    return st?.status === 'signed_in' ? st.user.ui_prefs : undefined;
  }

  /** Громкость 0..1: нормализация вниз к −14 LUFS и затухание кроссфейда в конце трека. */
  private async applyVolume(track: Track | null, fade: number) {
    const gain = Math.min(1, normalizeGain(track?.features?.loudness_lufs, this.userPrefs()?.normalize !== false) * fade);
    await TrackPlayer.setVolume(gain).catch(() => undefined);
  }

  private async toRntp(tracks: Track[]): Promise<RntpTrack[]> {
    const q = await quality();
    // Скачанный трек играется из файла (и без сети), остальные — стримом по качеству сети.
    return tracks.map((t) => {
      const cover = absolute(this.server, t.album.cover_url);
      return {
        id: t.id,
        url: downloads.localTrack(t.id) ?? `${absolute(this.server, t.stream_url)}&q=${q}`,
        title: t.title,
        artist: t.artists.map((a) => a.name).join(', '),
        album: t.album.title,
        artwork: downloads.localCover(t) ?? (cover ? sizedCover(cover, 300) : undefined),
        duration: t.duration_ms / 1000,
      };
    });
  }

  async playList(tracks: Track[], index: number, context: PlayContext) {
    const list = tracks.filter(playable);
    const target = tracks[index];
    if (!target || !list.length) return;
    await this.setup();
    this.leaveWave();
    this.finishAttempt(this.lastPositionMs / 1000);
    const start = Math.max(list.indexOf(target), 0);
    this.update({ queue: list, context, index: start, track: list[start] ?? null });
    await TrackPlayer.reset();
    await TrackPlayer.add(await this.toRntp(list));
    await TrackPlayer.skip(start);
    await TrackPlayer.play();
  }

  toggle() {
    void (this.state.playing ? TrackPlayer.pause() : TrackPlayer.play());
  }

  next() {
    void TrackPlayer.skipToNext().catch(() => undefined);
  }

  async prev() {
    const { position } = await TrackPlayer.getProgress();
    if (position > 3) await TrackPlayer.seekTo(0);
    else await TrackPlayer.skipToPrevious().catch(() => TrackPlayer.seekTo(0));
  }

  seek(ms: number) {
    const t = this.state.track;
    if (t) this.events?.push({ type: 'seek', track_id: t.id, from_ms: this.lastPositionMs, position_ms: ms });
    this.attempt?.seek(ms);
    this.lastPositionMs = ms;
    void TrackPlayer.seekTo(ms / 1000);
  }

  /** Реакция на трек: сразу в UI; без сети запоминается и уходит на сервер при появлении связи. */
  async react(track: Track, reaction: 'like' | 'dislike' | null) {
    if (!this.persistent) return;
    const prev = track.reaction;
    const apply = (r: Track['reaction']) => {
      this.update({
        queue: this.state.queue.map((t) => (t.id === track.id ? { ...t, reaction: r } : t)),
        track: this.state.track?.id === track.id ? { ...this.state.track, reaction: r } : this.state.track,
      });
      void downloads.setReaction(track.id, r);
    };
    apply(reaction);
    this.events?.push({ type: reaction ?? (prev === 'like' ? 'unlike' : 'undislike'), track_id: track.id });
    try {
      await this.persistent.react(track.id, reaction);
    } catch (e) {
      apply(prev);
      throw e;
    }
    if (reaction === 'like' && downloads.state.autoLikes) void downloads.enqueue([{ ...track, reaction }]);
    if (reaction) {
      this.noteWave(track.id, reaction);
      void this.refillWave(true);
    }
    if (reaction === 'dislike' && this.state.track?.id === track.id) this.next();
  }

  // --- «Моя волна» ---

  async startWave(activity: string | null, mood: string | null) {
    if (!this.session) return;
    await this.setup();
    this.leaveWave();
    const version = this.wavePolicy.version;
    let res;
    try {
      res = unwrap(await this.session.client.POST('/api/v1/wave/sessions', { body: { activity, mood } }));
    } catch (e) {
      if (!this.wavePolicy.isCurrent(version)) return;
      // Нет связи с сервером — офлайн-волна из скачанного.
      const local = offlineWave(downloads.downloaded());
      if (!local.length) throw e;
      return this.playList(local, 0, { type: 'collection', id: 'downloads' });
    }
    if (!this.wavePolicy.isCurrent(version)) return;
    const tracks = res.tracks.filter(playable);
    if (!tracks.length) return;
    this.finishAttempt(this.lastPositionMs / 1000);
    this.wavePolicy.activate(res.session_id);
    this.update({
      queue: tracks, index: 0, track: tracks[0] ?? null, context: { type: 'wave', id: res.session_id },
      wave: { sessionId: res.session_id, activity: res.activity, mood: res.mood, fallback: res.fallback },
    });
    await TrackPlayer.reset();
    await TrackPlayer.add(await this.toRntp(tracks));
    await TrackPlayer.play();
  }

  async setWaveContext(activity: string | null, mood: string | null) {
    const wave = this.state.wave;
    if (!wave || !this.session) return this.startWave(activity, mood);
    const version = this.wavePolicy.changeContext(wave.sessionId);
    const res = unwrap(
      await this.session.client.PATCH('/api/v1/wave/sessions/{id}', {
        params: { path: { id: wave.sessionId } },
        body: { activity, mood },
      }),
    );
    if (!this.wavePolicy.isCurrent(version)) return;
    await this.replaceUpcoming(res.tracks, () => this.wavePolicy.isCurrent(version));
    if (!this.wavePolicy.isCurrent(version)) return;
    this.update({ wave: { ...wave, activity: res.activity, mood: res.mood, fallback: res.fallback } });
    // Новый контекст звучит сразу; прерванный трек — не скип для волны (как в вебе).
    if (res.tracks.some(playable)) {
      this.neutralSwitch = true;
      await TrackPlayer.skipToNext().catch(() => {
        this.neutralSwitch = false;
      });
    }
  }

  private leaveWave() {
    const wave = this.state.wave;
    this.wavePolicy.activate(null);
    if (!wave) return;
    this.update({ wave: null });
    void this.session?.client
      .DELETE('/api/v1/wave/sessions/{id}', { params: { path: { id: wave.sessionId } } })
      .catch(() => undefined);
  }

  private noteWave(trackId: string, outcome: WaveOutcome) {
    this.wavePolicy.note(trackId, outcome);
  }

  /** Убрать не начатые треки и поставить новые (после реакции или смены контекста). */
  private async replaceUpcoming(tracks: Track[], current: () => boolean = () => true) {
    const keep = this.state.queue.slice(0, this.state.index + 1);
    const add = tracks.filter(playable);
    const native = await this.toRntp(add);
    if (!current()) return;
    await TrackPlayer.removeUpcomingTracks();
    if (!current()) return;
    await TrackPlayer.add(native);
    if (current()) this.update({ queue: [...keep, ...add] });
  }

  private async refillWave(refresh = false) {
    if (!this.session) return;
    const remaining = this.state.queue.length - this.state.index - 1;
    await this.wavePolicy.refill(remaining, refresh, async (res, current) => {
      if (refresh) await this.replaceUpcoming(res.tracks, current);
      else {
        const add = res.tracks.filter(playable);
        const native = await this.toRntp(add);
        if (!current()) return;
        await TrackPlayer.add(native);
        if (!current()) return;
        this.update({ queue: [...this.state.queue, ...add] });
      }
      if (current()) this.update({ wave: { ...this.state.wave!, fallback: res.fallback } });
    });
  }

  // --- состояние ---

  private save() {
    const t = this.state.track;
    if (!t || !this.session) return;
    this.lastSave = Date.now();
    void this.session.client
      .PUT('/api/v1/me/playback-state', {
        body: {
          track_id: t.id,
          position_ms: this.lastPositionMs,
          queue: this.state.queue.slice(0, 500).map((x) => x.id),
          queue_index: Math.min(this.state.index, 499),
          context: this.state.context ? { type: this.state.context.type, id: this.state.context.id } : undefined,
          device_id: 'android',
        },
      })
      .catch(() => undefined);
  }

  /** Восстановить последний трек и позицию (на паузе, без автозапуска). */
  async restore() {
    if (!this.session || this.state.track) return;
    await this.setup();
    try {
      const st = unwrap(await this.session.client.GET('/api/v1/me/playback-state'));
      if (!st.track_id || !st.queue.length) return;
      const res = unwrap(await this.session.client.POST('/api/v1/tracks/batch', { body: { ids: st.queue } }));
      const tracks = res.items.filter(playable);
      const idx = Math.max(tracks.findIndex((t) => t.id === st.track_id), 0);
      if (!tracks.length) return;
      this.update({ queue: tracks, index: idx, track: tracks[idx] ?? null, context: (st.context as PlayContext | null) ?? null });
      await TrackPlayer.reset();
      await TrackPlayer.add(await this.toRntp(tracks));
      await TrackPlayer.skip(idx, tracks[idx]?.id === st.track_id ? st.position_ms / 1000 : 0);
    } catch {
      // офлайн или нет сохранённого состояния
    }
  }

  async reset() {
    this.wavePolicy.activate(null);
    this.attempt = null;
    this.update({ queue: [], track: null, index: 0, playing: false, positionMs: 0, wave: null, context: null });
    if (this.setupDone) await TrackPlayer.reset().catch(() => undefined);
  }

  flush() {
    this.save();
    void this.events?.flush();
  }
}

export const player = new Controller();