"use client";

import {
  createContext,
  useContext,
  useRef,
  useState,
  useCallback,
  useEffect,
  type ReactNode,
} from "react";
import { useAuth } from "@/components/auth/auth-provider";
import {
  trackKey,
  loadAllProgress,
  saveProgress,
  removeProgress,
  syncLocalToRemote,
  type ProgressEntry,
} from "@/lib/audio-progress";
import {
  primeOfflineAudio,
  offlineAudioURL,
  releaseOfflineAudio,
} from "@/lib/offline";

/**
 * Resolve the media source for a track: prefer a saved offline object URL
 * (works with no network + full seeking) and fall back to the remote URL.
 */
function resolveSrc(url: string): string {
  return offlineAudioURL(trackKey(url)) ?? url;
}

// ---------------------------------------------------------------------------
// Types
// ---------------------------------------------------------------------------

export type AudioTrack = {
  url: string;
  title: string;
  subtitle?: string;
  coverImage?: string;
  sourceUrl?: string;
  type?: "lecture" | "conversation" | "kirtan" | "music" | string;
};

type AudioPlayerState = {
  currentTrack: AudioTrack | null;
  isPlaying: boolean;
  currentTime: number;
  duration: number;
  volume: number;
  isMuted: boolean;
  isLoading: boolean;
  playlist: AudioTrack[];
  currentIndex: number;
};

type AudioPlayerActions = {
  play: (track: AudioTrack) => void;
  playPlaylist: (tracks: AudioTrack[], startIndex?: number) => void;
  /**
   * Gives the track that's already playing a queue to sit in, without
   * restarting it — for a queue that arrives after playback began. Ignored
   * if the current track isn't in it (the user moved on meanwhile).
   */
  attachQueue: (tracks: AudioTrack[]) => void;
  pause: () => void;
  resume: () => void;
  togglePlayPause: () => void;
  stop: () => void;
  seekTo: (time: number) => void;
  setVolume: (vol: number) => void;
  toggleMute: () => void;
  next: () => void;
  previous: () => void;
};

type AudioPlayerContextValue = AudioPlayerState & AudioPlayerActions;

// ---------------------------------------------------------------------------
// Context
// ---------------------------------------------------------------------------

const AudioPlayerContext = createContext<AudioPlayerContextValue | null>(null);

// ---------------------------------------------------------------------------
// localStorage helpers
// ---------------------------------------------------------------------------

const VOLUME_KEY = "audio-player-volume";
const MUTED_KEY = "audio-player-muted";

// Playback-resume tuning. Persist at most once every SAVE_INTERVAL_MS while
// playing (discrete events — pause/close/tab-hide — always flush immediately).
// Positions within RESUME_END_GUARD_S of the end are treated as "finished":
// never saved and never resumed, so a completed track restarts from 0.
const SAVE_INTERVAL_MS = 5000;
const RESUME_END_GUARD_S = 5;

function readStoredVolume(): number {
  if (typeof window === "undefined") return 0.75;
  try {
    const raw = localStorage.getItem(VOLUME_KEY);
    if (raw !== null) {
      const v = parseFloat(raw);
      if (isFinite(v) && v >= 0 && v <= 1) return v;
    }
  } catch {
    // localStorage unavailable
  }
  return 0.75;
}

function readStoredMuted(): boolean {
  if (typeof window === "undefined") return false;
  try {
    return localStorage.getItem(MUTED_KEY) === "true";
  } catch {
    return false;
  }
}

function persistVolume(vol: number) {
  try {
    localStorage.setItem(VOLUME_KEY, String(vol));
  } catch {
    // ignore
  }
}

function persistMuted(muted: boolean) {
  try {
    localStorage.setItem(MUTED_KEY, String(muted));
  } catch {
    // ignore
  }
}

// ---------------------------------------------------------------------------
// Provider
// ---------------------------------------------------------------------------

export function AudioPlayerProvider({ children }: { children: ReactNode }) {
  const audioRef = useRef<HTMLAudioElement>(null);

  // --- State ---
  const [currentTrack, setCurrentTrack] = useState<AudioTrack | null>(null);
  const [isPlaying, setIsPlaying] = useState(false);
  const [currentTime, setCurrentTime] = useState(0);
  const [duration, setDuration] = useState(0);
  const [volume, setVolumeState] = useState(readStoredVolume);
  const [isMuted, setIsMuted] = useState(readStoredMuted);
  const [isLoading, setIsLoading] = useState(false);
  const [playlist, setPlaylist] = useState<AudioTrack[]>([]);
  const [currentIndex, setCurrentIndex] = useState(-1);

  // Keep refs for values accessed in callbacks to avoid stale closures
  const playlistRef = useRef(playlist);
  const currentIndexRef = useRef(currentIndex);

  // --- Playback-resume memory ---
  const { user, loading: authLoading } = useAuth();
  const authedRef = useRef(false);
  useEffect(() => {
    authedRef.current = !!user;
  }, [user]);

  // The track currently loaded into the <audio> element. Set synchronously
  // wherever we swap `audio.src` so the event handlers (which run before the
  // React state settles) always read the right file identity.
  const currentTrackRef = useRef<AudioTrack | null>(null);
  // key → last-known resume point. Read synchronously on load to seek; every
  // save write-throughs here and to the persistent store.
  const progressRef = useRef<Map<string, ProgressEntry>>(new Map());
  const lastFlushRef = useRef(0);
  // null until the first hydrate settles; then tracks the previous auth state
  // so we can detect the anon→signed-in transition and sync IndexedDB up once.
  const wasAuthedRef = useRef<boolean | null>(null);

  // Hydrate the in-memory map from the active store (BFF when signed in,
  // IndexedDB otherwise). On the anon→signed-in flip, push local entries up
  // first (newest-wins merge) so anonymous progress follows the account.
  useEffect(() => {
    if (authLoading) return;
    const authed = !!user;
    let cancelled = false;
    (async () => {
      try {
        if (authed && wasAuthedRef.current === false) {
          await syncLocalToRemote();
        }
        const entries = await loadAllProgress(authed);
        if (cancelled) return;
        const map = new Map<string, ProgressEntry>();
        for (const e of entries) map.set(e.key, e);
        progressRef.current = map;
      } catch {
        // best-effort — resume simply has no data if this fails
      } finally {
        if (!cancelled) wasAuthedRef.current = authed;
      }
    })();
    return () => {
      cancelled = true;
    };
  }, [user, authLoading]);

  // Record the current position into the in-memory map. Returns the entry to
  // flush, or undefined when there's nothing worth saving (no track, position
  // < 1s, or within the end-guard i.e. effectively finished).
  const recordProgress = useCallback(
    (
      track: AudioTrack | null,
      position: number,
      dur: number,
    ): ProgressEntry | undefined => {
      if (!track || !isFinite(position) || position < 1) return undefined;
      const duration = isFinite(dur) && dur > 0 ? dur : undefined;
      if (duration !== undefined && position >= duration - RESUME_END_GUARD_S) {
        return undefined;
      }
      const entry: ProgressEntry = {
        key: trackKey(track.url),
        position,
        duration,
        updated_at: new Date().toISOString(),
      };
      progressRef.current.set(entry.key, entry);
      return entry;
    },
    [],
  );

  // Persist an entry to the active store (fire-and-forget).
  const flush = useCallback(
    (entry: ProgressEntry | undefined, opts?: { keepalive?: boolean }) => {
      if (!entry) return;
      void saveProgress(entry, authedRef.current, opts).catch(() => {});
    },
    [],
  );

  // Snapshot + persist the currently-playing track's position immediately.
  // Used on pause, close, track-switch, and tab-hide.
  const saveCurrent = useCallback(
    (opts?: { keepalive?: boolean }) => {
      const audio = audioRef.current;
      if (!audio) return;
      flush(recordProgress(currentTrackRef.current, audio.currentTime, audio.duration), opts);
    },
    [recordProgress, flush],
  );

  // Sync refs in an effect to avoid "cannot access refs during render"
  useEffect(() => {
    playlistRef.current = playlist;
  }, [playlist]);
  useEffect(() => {
    currentIndexRef.current = currentIndex;
  }, [currentIndex]);

  // Build object URLs for any audio saved offline so `resolveSrc` can prefer
  // them synchronously at play time (offline playback + full seeking).
  useEffect(() => {
    void primeOfflineAudio();
    return () => releaseOfflineAudio();
  }, []);

  // --- Sync volume/muted to the <audio> element ---
  useEffect(() => {
    const audio = audioRef.current;
    if (!audio) return;
    audio.volume = isMuted ? 0 : volume;
  }, [volume, isMuted]);

  // --- Audio event listeners ---
  useEffect(() => {
    const audio = audioRef.current;
    if (!audio) return;

    function handleTimeUpdate() {
      setCurrentTime(audio!.currentTime);
      // Throttled resume-point save while playing.
      const entry = recordProgress(
        currentTrackRef.current,
        audio!.currentTime,
        audio!.duration,
      );
      const now = Date.now();
      if (entry && now - lastFlushRef.current >= SAVE_INTERVAL_MS) {
        lastFlushRef.current = now;
        flush(entry);
      }
    }

    function handleLoadedMetadata() {
      setDuration(audio!.duration);
      // Resume: if this file has a saved position that isn't at/near the end,
      // seek there before playback gets going.
      const track = currentTrackRef.current;
      if (!track) return;
      const saved = progressRef.current.get(trackKey(track.url));
      if (!saved) return;
      const dur = audio!.duration;
      const pos = saved.position;
      if (pos > 1 && (!isFinite(dur) || pos < dur - RESUME_END_GUARD_S)) {
        try {
          audio!.currentTime = pos;
          setCurrentTime(pos);
        } catch {
          // seeking may throw if the source isn't seekable yet; ignore
        }
      }
    }

    function handleDurationChange() {
      if (isFinite(audio!.duration)) {
        setDuration(audio!.duration);
      }
    }

    function handleCanPlay() {
      setIsLoading(false);
    }

    function handleWaiting() {
      setIsLoading(true);
    }

    function handlePlaying() {
      setIsPlaying(true);
      setIsLoading(false);
    }

    function handlePause() {
      setIsPlaying(false);
    }

    function handleEnded() {
      setIsPlaying(false);
      // Finished — drop this file's resume point so it restarts from 0.
      const finished = currentTrackRef.current;
      if (finished) {
        const k = trackKey(finished.url);
        progressRef.current.delete(k);
        void removeProgress(k, authedRef.current).catch(() => {});
      }
      // Auto-play next track if playlist has more
      const idx = currentIndexRef.current;
      const pl = playlistRef.current;
      if (idx >= 0 && idx < pl.length - 1) {
        const nextIdx = idx + 1;
        const nextTrack = pl[nextIdx];
        currentTrackRef.current = nextTrack;
        setCurrentIndex(nextIdx);
        setCurrentTrack(nextTrack);
        setCurrentTime(0);
        setDuration(0);
        setIsLoading(true);
        if (audio) {
          audio.src = resolveSrc(nextTrack.url);
          audio.load();
          audio.play().catch((err) => {
            console.error("[AudioPlayer] Auto-play next failed:", err);
            setIsPlaying(false);
            setIsLoading(false);
          });
        }
      }
    }

    function handleError() {
      console.error("[AudioPlayer] Audio error:", audio!.error);
      setIsPlaying(false);
      setIsLoading(false);
    }

    audio.addEventListener("timeupdate", handleTimeUpdate);
    audio.addEventListener("loadedmetadata", handleLoadedMetadata);
    audio.addEventListener("durationchange", handleDurationChange);
    audio.addEventListener("canplay", handleCanPlay);
    audio.addEventListener("waiting", handleWaiting);
    audio.addEventListener("playing", handlePlaying);
    audio.addEventListener("pause", handlePause);
    audio.addEventListener("ended", handleEnded);
    audio.addEventListener("error", handleError);

    return () => {
      audio.removeEventListener("timeupdate", handleTimeUpdate);
      audio.removeEventListener("loadedmetadata", handleLoadedMetadata);
      audio.removeEventListener("durationchange", handleDurationChange);
      audio.removeEventListener("canplay", handleCanPlay);
      audio.removeEventListener("waiting", handleWaiting);
      audio.removeEventListener("playing", handlePlaying);
      audio.removeEventListener("pause", handlePause);
      audio.removeEventListener("ended", handleEnded);
      audio.removeEventListener("error", handleError);
    };
  }, [recordProgress, flush]);

  // Flush the current position when the tab is hidden or the page is being
  // unloaded (browser/tab close, refresh, navigation) — the last line of
  // defence on top of the throttled in-play saves. `keepalive` lets the
  // request outlive the page for signed-in users.
  useEffect(() => {
    const flushNow = () => saveCurrent({ keepalive: true });
    const onVisibility = () => {
      if (document.visibilityState === "hidden") flushNow();
    };
    window.addEventListener("pagehide", flushNow);
    document.addEventListener("visibilitychange", onVisibility);
    return () => {
      window.removeEventListener("pagehide", flushNow);
      document.removeEventListener("visibilitychange", onVisibility);
    };
  }, [saveCurrent]);

  // --- Actions ---

  const play = useCallback(
    (track: AudioTrack) => {
      const audio = audioRef.current;
      if (!audio) return;

      // Save the outgoing track's position before swapping sources.
      saveCurrent();
      currentTrackRef.current = track;

      setCurrentTrack(track);
      setPlaylist([track]);
      setCurrentIndex(0);
      setCurrentTime(0);
      setDuration(0);
      setIsLoading(true);

      audio.src = resolveSrc(track.url);
      audio.load();
      audio.play().catch((err) => {
        console.error("[AudioPlayer] Play failed:", err);
        setIsPlaying(false);
        setIsLoading(false);
      });
    },
    [saveCurrent],
  );

  const playPlaylist = useCallback(
    (tracks: AudioTrack[], startIndex: number = 0) => {
      const audio = audioRef.current;
      if (!audio || tracks.length === 0) return;

      const idx = Math.max(0, Math.min(startIndex, tracks.length - 1));
      const track = tracks[idx];

      saveCurrent();
      currentTrackRef.current = track;

      setPlaylist(tracks);
      setCurrentIndex(idx);
      setCurrentTrack(track);
      setCurrentTime(0);
      setDuration(0);
      setIsLoading(true);

      audio.src = resolveSrc(track.url);
      audio.load();
      audio.play().catch((err) => {
        console.error("[AudioPlayer] PlayPlaylist failed:", err);
        setIsPlaying(false);
        setIsLoading(false);
      });
    },
    [saveCurrent],
  );

  const attachQueue = useCallback((tracks: AudioTrack[]) => {
    const current = currentTrackRef.current;
    const idx = current ? tracks.findIndex((t) => t.url === current.url) : -1;
    if (idx < 0) return;
    setPlaylist(tracks);
    setCurrentIndex(idx);
  }, []);

  const pause = useCallback(() => {
    audioRef.current?.pause();
    saveCurrent();
  }, [saveCurrent]);

  const resume = useCallback(() => {
    const audio = audioRef.current;
    if (!audio || !audio.src) return;
    audio.play().catch((err) => {
      console.error("[AudioPlayer] Resume failed:", err);
      setIsPlaying(false);
    });
  }, []);

  const togglePlayPause = useCallback(() => {
    const audio = audioRef.current;
    if (!audio || !audio.src) return;
    if (audio.paused) {
      audio.play().catch((err) => {
        console.error("[AudioPlayer] Toggle play failed:", err);
        setIsPlaying(false);
      });
    } else {
      audio.pause();
      saveCurrent();
    }
  }, [saveCurrent]);

  const stop = useCallback(() => {
    const audio = audioRef.current;
    if (audio) {
      // Capture the resume point before we tear the source down.
      saveCurrent({ keepalive: true });
      audio.pause();
      audio.removeAttribute("src");
      audio.load();
    }
    currentTrackRef.current = null;
    setCurrentTrack(null);
    setIsPlaying(false);
    setCurrentTime(0);
    setDuration(0);
    setIsLoading(false);
    setPlaylist([]);
    setCurrentIndex(-1);
  }, [saveCurrent]);

  const seekTo = useCallback((time: number) => {
    const audio = audioRef.current;
    if (!audio) return;
    const clamped = Math.max(0, Math.min(time, audio.duration || 0));
    audio.currentTime = clamped;
    setCurrentTime(clamped);
  }, []);

  const setVolume = useCallback(
    (vol: number) => {
      const clamped = Math.max(0, Math.min(1, vol));
      setVolumeState(clamped);
      persistVolume(clamped);
      // If setting volume while muted, unmute
      if (isMuted && clamped > 0) {
        setIsMuted(false);
        persistMuted(false);
      }
    },
    [isMuted],
  );

  const toggleMute = useCallback(() => {
    setIsMuted((prev) => {
      const next = !prev;
      persistMuted(next);
      return next;
    });
  }, []);

  const next = useCallback(() => {
    const audio = audioRef.current;
    const idx = currentIndexRef.current;
    const pl = playlistRef.current;

    if (!audio || idx < 0 || idx >= pl.length - 1) return;

    const nextIdx = idx + 1;
    const nextTrack = pl[nextIdx];

    saveCurrent();
    currentTrackRef.current = nextTrack;

    setCurrentIndex(nextIdx);
    setCurrentTrack(nextTrack);
    setCurrentTime(0);
    setDuration(0);
    setIsLoading(true);

    audio.src = resolveSrc(nextTrack.url);
    audio.load();
    audio.play().catch((err) => {
      console.error("[AudioPlayer] Next failed:", err);
      setIsPlaying(false);
      setIsLoading(false);
    });
  }, [saveCurrent]);

  const previous = useCallback(() => {
    const audio = audioRef.current;
    const idx = currentIndexRef.current;
    const pl = playlistRef.current;

    if (!audio || idx < 0) return;

    // If more than 3 seconds in, restart the current track instead
    if (audio.currentTime > 3) {
      audio.currentTime = 0;
      setCurrentTime(0);
      return;
    }

    if (idx <= 0) {
      // At start of playlist — just restart
      audio.currentTime = 0;
      setCurrentTime(0);
      return;
    }

    const prevIdx = idx - 1;
    const prevTrack = pl[prevIdx];

    saveCurrent();
    currentTrackRef.current = prevTrack;

    setCurrentIndex(prevIdx);
    setCurrentTrack(prevTrack);
    setCurrentTime(0);
    setDuration(0);
    setIsLoading(true);

    audio.src = resolveSrc(prevTrack.url);
    audio.load();
    audio.play().catch((err) => {
      console.error("[AudioPlayer] Previous failed:", err);
      setIsPlaying(false);
      setIsLoading(false);
    });
  }, [saveCurrent]);

  // --- Context value ---

  const value: AudioPlayerContextValue = {
    currentTrack,
    isPlaying,
    currentTime,
    duration,
    volume,
    isMuted,
    isLoading,
    playlist,
    currentIndex,
    play,
    playPlaylist,
    attachQueue,
    pause,
    resume,
    togglePlayPause,
    stop,
    seekTo,
    setVolume,
    toggleMute,
    next,
    previous,
  };

  return (
    <AudioPlayerContext.Provider value={value}>
      {children}
      <audio ref={audioRef} preload="metadata" style={{ display: "none" }} />
    </AudioPlayerContext.Provider>
  );
}

// ---------------------------------------------------------------------------
// Hook
// ---------------------------------------------------------------------------

export function useAudioPlayer(): AudioPlayerContextValue {
  const ctx = useContext(AudioPlayerContext);
  if (!ctx) {
    throw new Error(
      "useAudioPlayer must be used within an <AudioPlayerProvider>",
    );
  }
  return ctx;
}