import React, { useEffect, useState, useCallback, useMemo } from 'react';
import { useParams, useNavigate } from 'react-router-dom';
import { invoke } from '@tauri-apps/api/core';
import { getAlbum, getArtist, getArtistInfo, setRating, buildCoverArtUrl, coverArtCacheKey, buildDownloadUrl, star, unstar, SubsonicSong, SubsonicAlbum } from '../api/subsonic';
import { usePlayerStore, songToTrack } from '../store/playerStore';
import { useAuthStore } from '../store/authStore';
import { useDownloadModalStore } from '../store/downloadModalStore';
import { useOfflineStore } from '../store/offlineStore';
import { writeFile } from '@tauri-apps/plugin-fs';
import { join } from '@tauri-apps/api/path';
import AlbumCard from '../components/AlbumCard';
import AlbumHeader from '../components/AlbumHeader';
import AlbumTrackList from '../components/AlbumTrackList';
import { useCachedUrl } from '../components/CachedImage';
import { useTranslation } from 'react-i18next';

function sanitizeFilename(name: string): string {
  return name
    .replace(/[/\\?%*:|"<>]/g, '-')
    .replace(/\.{2,}/g, '.')
    .replace(/^[\s.]+|[\s.]+$/g, '')
    .substring(0, 200) || 'download';
}

export default function AlbumDetail() {
  const { t } = useTranslation();
  const { id } = useParams<{ id: string }>();
  const navigate = useNavigate();
  const auth = useAuthStore();
  const requestDownloadFolder = useDownloadModalStore(s => s.requestFolder);
  const playTrack = usePlayerStore(s => s.playTrack);
  const enqueue = usePlayerStore(s => s.enqueue);
  const openContextMenu = usePlayerStore(s => s.openContextMenu);
  const starredOverrides = usePlayerStore(s => s.starredOverrides);
  const setStarredOverride = usePlayerStore(s => s.setStarredOverride);
  const currentTrack = usePlayerStore(s => s.currentTrack);
  const isPlaying = usePlayerStore(s => s.isPlaying);

  const [album, setAlbum] = useState<Awaited<ReturnType<typeof getAlbum>> | null>(null);
  const [relatedAlbums, setRelatedAlbums] = useState<SubsonicAlbum[]>([]);
  const [ratings, setRatings] = useState<Record<string, number>>({});
  const [bio, setBio] = useState<string | null>(null);
  const [bioOpen, setBioOpen] = useState(false);
  const [loading, setLoading] = useState(true);
  const [downloadProgress, setDownloadProgress] = useState<number | null>(null);
  const [isStarred, setIsStarred] = useState(false);
  const [starredSongs, setStarredSongs] = useState<Set<string>>(new Set());
  const [offlineStorageFull, setOfflineStorageFull] = useState(false);

  const { downloadAlbum, deleteAlbum } = useOfflineStore();
  const offlineTracks = useOfflineStore(s => s.tracks);
  const offlineAlbums = useOfflineStore(s => s.albums);
  const offlineJobs = useOfflineStore(s => s.jobs);
  const serverId = auth.activeServerId ?? '';

  const offlineStatus: 'none' | 'downloading' | 'cached' = (() => {
    if (!album) return 'none';
    const meta = offlineAlbums[`${serverId}:${album.album.id}`];
    const isDownloaded = meta && meta.trackIds.length > 0 && meta.trackIds.every(tid => !!offlineTracks[`${serverId}:${tid}`]);
    if (isDownloaded) return 'cached';
    const isDownloading = offlineJobs.some(j => j.albumId === album.album.id && (j.status === 'queued' || j.status === 'downloading'));
    return isDownloading ? 'downloading' : 'none';
  })();

  const offlineProgress = (() => {
    if (!album) return null;
    const albumJobs = offlineJobs.filter(j => j.albumId === album.album.id);
    if (albumJobs.length === 0) return null;
    const done = albumJobs.filter(j => j.status === 'done' || j.status === 'error').length;
    return { done, total: albumJobs.length };
  })();

  useEffect(() => {
    if (!id) return;
    setLoading(true);
    setRelatedAlbums([]);
    getAlbum(id).then(async data => {
      setAlbum(data);
      setIsStarred(!!data.album.starred);
      const initialStarred = new Set<string>();
      data.songs.forEach(s => { if (s.starred) initialStarred.add(s.id); });
      setStarredSongs(initialStarred);
      setLoading(false);
      try {
        const artistData = await getArtist(data.album.artistId);
        setRelatedAlbums(artistData.albums.filter(a => a.id !== id));
      } catch (e) {
        console.error('Failed to fetch related albums', e);
      }
    }).catch(() => setLoading(false));
  }, [id]);

const handlePlayAll = () => {
     if (!album) return;
     const albumGenre = album.album.genre;
     const tracks = album.songs.map(s => {
       const t = songToTrack(s);
       if (!t.genre && albumGenre) t.genre = albumGenre;
       return t;
     });
     if (tracks[0]) playTrack(tracks[0], tracks);
   };

const handleEnqueueAll = () => {
     if (!album) return;
     const albumGenre = album.album.genre;
     const tracks = album.songs.map(s => {
       const t = songToTrack(s);
       if (!t.genre && albumGenre) t.genre = albumGenre;
       return t;
     });
     enqueue(tracks);
   };

   const handlePlaySong = (song: SubsonicSong) => {
     if (!album) return;
     const albumGenre = album.album.genre;
     const tracks = album.songs.map(s => {
       const t = songToTrack(s);
       if (!t.genre && albumGenre) t.genre = albumGenre;
       return t;
     });
     const track = tracks.find(t => t.id === song.id) || songToTrack(song);
     playTrack(track, tracks);
   };

  const handleRate = async (songId: string, rating: number) => {
    setRatings(r => ({ ...r, [songId]: rating }));
    await setRating(songId, rating);
  };

  const handleBio = async () => {
    if (!album) return;
    if (bio) { setBioOpen(true); return; }
    const info = await getArtistInfo(album.album.artistId);
    setBio(info.biography ?? t('albumDetail.noBio'));
    setBioOpen(true);
  };

  const handleDownload = async () => {
    if (!album) return;
    const { name, id: albumId } = album.album;

    // Ask for folder before starting download if not already set
    const folder = auth.downloadFolder || await requestDownloadFolder();
    if (!folder) return;

    setDownloadProgress(0);
    try {
      const url = buildDownloadUrl(albumId);
      const response = await fetch(url);
      if (!response.ok) throw new Error(`HTTP ${response.status}`);

      const contentLength = response.headers.get('Content-Length');
      const total = contentLength ? parseInt(contentLength, 10) : 0;
      const chunks: Uint8Array<ArrayBuffer>[] = [];

      if (total && response.body) {
        const reader = response.body.getReader();
        let received = 0;
        while (true) {
          const { done, value } = await reader.read();
          if (done) break;
          chunks.push(value);
          received += value.length;
          setDownloadProgress(Math.round((received / total) * 100));
        }
      } else {
        const buffer = await response.arrayBuffer() as ArrayBuffer;
        chunks.push(new Uint8Array(buffer));
        setDownloadProgress(100);
      }

      const blob = new Blob(chunks);
      const buffer = await blob.arrayBuffer();
      const path = await join(folder, `${sanitizeFilename(name)}.zip`);
      await writeFile(path, new Uint8Array(buffer));
    } catch (e) {
      console.error('Download failed:', e);
      setDownloadProgress(null);
    } finally {
      setTimeout(() => setDownloadProgress(null), 60000);
    }
  };

  const toggleStar = async () => {
    if (!album) return;
    const wasStarred = isStarred;
    setIsStarred(!wasStarred);
    try {
      if (wasStarred) await unstar(album.album.id);
      else await star(album.album.id);
    } catch (e) {
      console.error('Failed to toggle star', e);
      setIsStarred(wasStarred);
    }
  };

  const toggleSongStar = async (song: SubsonicSong, e: React.MouseEvent) => {
    e.stopPropagation();
    const wasStarred = starredSongs.has(song.id);
    const next = new Set(starredSongs);
    if (wasStarred) next.delete(song.id); else next.add(song.id);
    setStarredSongs(next);
    setStarredOverride(song.id, !wasStarred);
    try {
      if (wasStarred) await unstar(song.id, 'song');
      else await star(song.id, 'song');
    } catch (err) {
      console.error('Failed to toggle song star', err);
      setStarredSongs(new Set(starredSongs));
      setStarredOverride(song.id, wasStarred);
    }
  };

  const handleCacheOffline = useCallback(async () => {
    if (!album) return;
    const maxBytes = auth.maxCacheMb * 1024 * 1024;
    try {
      const usedBytes = await invoke<number>('get_offline_cache_size');
      if (usedBytes >= maxBytes) {
        setOfflineStorageFull(true);
        return;
      }
    } catch {
      // If we can't check, proceed anyway
    }
    setOfflineStorageFull(false);
    downloadAlbum(album.album.id, album.album.name, album.album.artist, album.album.coverArt, album.album.year, album.songs, serverId);
  }, [album, auth.maxCacheMb, downloadAlbum, serverId]);

  const handleRemoveOffline = () => {
    if (!album) return;
    deleteAlbum(album.album.id, serverId);
  };

  // Hooks must be called unconditionally — derive from nullable album state.
  // useMemo is required: buildCoverArtUrl generates a new salt on every call, so without
  // memoization every re-render (e.g. currentTrack change) produces a new fetchUrl,
  // which cancels and restarts the useCachedUrl effect → background never resolves.
  const coverUrl = useMemo(() => album?.album.coverArt ? buildCoverArtUrl(album.album.coverArt, 400) : '', [album?.album.coverArt]);
  const coverKey = useMemo(() => album?.album.coverArt ? coverArtCacheKey(album.album.coverArt, 400) : '', [album?.album.coverArt]);
  const resolvedCoverUrl = useCachedUrl(coverUrl, coverKey);

  if (loading) return <div className="loading-center"><div className="spinner" /></div>;
  if (!album) return <div className="empty-state">{t('albumDetail.notFound')}</div>;

  const { album: info, songs } = album;
  const hasVariousArtists = songs.some(s => s.artist !== info.artist);

  return (
    <div className="album-detail animate-fade-in">
      <AlbumHeader
        info={info}
        songs={songs}
        coverUrl={coverUrl}
        coverKey={coverKey}
        resolvedCoverUrl={resolvedCoverUrl}
        isStarred={isStarred}
        downloadProgress={downloadProgress}
        bio={bio}
        bioOpen={bioOpen}
        onToggleStar={toggleStar}
        onDownload={handleDownload}
        onPlayAll={handlePlayAll}
        onEnqueueAll={handleEnqueueAll}
        onBio={handleBio}
        onCloseBio={() => setBioOpen(false)}
        offlineStatus={offlineStatus}
        offlineProgress={offlineProgress}
        onCacheOffline={handleCacheOffline}
        onRemoveOffline={handleRemoveOffline}
      />
      {offlineStorageFull && (
        <div className="offline-storage-full-banner" role="alert">
          <span>{t('albumDetail.offlineStorageFull', { mb: auth.maxCacheMb })}</span>
          <button className="btn btn-ghost" style={{ fontSize: 13 }} onClick={() => navigate('/offline')}>
            {t('albumDetail.offlineStorageGoToLibrary')}
          </button>
          <button className="btn btn-ghost" style={{ fontSize: 13 }} onClick={() => navigate('/settings', { state: { tab: 'library' } })}>
            {t('albumDetail.offlineStorageGoToSettings')}
          </button>
          <button className="offline-storage-full-dismiss" onClick={() => setOfflineStorageFull(false)} aria-label="Dismiss">×</button>
        </div>
      )}

      <AlbumTrackList
        songs={songs}
        hasVariousArtists={hasVariousArtists}
        currentTrack={currentTrack}
        isPlaying={isPlaying}
        ratings={ratings}
        starredSongs={new Set([
          ...[...starredSongs].filter(id => starredOverrides[id] !== false),
          ...Object.entries(starredOverrides).filter(([, v]) => v).map(([k]) => k),
        ])}
        onPlaySong={handlePlaySong}
        onRate={handleRate}
        onToggleSongStar={toggleSongStar}
        onContextMenu={openContextMenu}
      />

      {relatedAlbums.length > 0 && (
        <div className="album-related">
          <div className="album-related-divider" />
          <h2 className="section-title album-related-title">{t('albumDetail.moreByArtist', { artist: info.artist })}</h2>
          <div className="album-grid-wrap">
            {relatedAlbums.map(a => <AlbumCard key={a.id} album={a} />)}
          </div>
        </div>
      )}
    </div>
  );
}
