const { db } = require('../../db');
const notifications = require('./notifications');

// ── Lookup statements for notification context ───────────────────────────────
const songOwnerStmt     = db.prepare('SELECT uploaded_by, title, slug FROM songs WHERE id = ?');
const playlistOwnerStmt = db.prepare('SELECT created_by, title, slug FROM playlists WHERE id = ?');
const userNameStmt      = db.prepare('SELECT display_name FROM users WHERE id = ?');

function getActorName(actorId) {
  return actorId ? (userNameStmt.get(actorId)?.display_name || null) : null;
}

// ── Song statements ──────────────────────────────────────────────────────────
const songLikeCountStmt     = db.prepare('SELECT COUNT(*) AS c FROM song_likes WHERE song_id = ?');
const songFavCountStmt      = db.prepare('SELECT COUNT(*) AS c FROM song_favorites WHERE song_id = ?');
const songUserLikedStmt     = db.prepare('SELECT 1 FROM song_likes WHERE user_id = ? AND song_id = ?');
const songUserFavoritedStmt = db.prepare('SELECT 1 FROM song_favorites WHERE user_id = ? AND song_id = ?');
const insertSongLike        = db.prepare('INSERT OR IGNORE INTO song_likes (user_id, song_id) VALUES (?, ?)');
const deleteSongLike        = db.prepare('DELETE FROM song_likes WHERE user_id = ? AND song_id = ?');
const insertSongFav         = db.prepare('INSERT OR IGNORE INTO song_favorites (user_id, song_id) VALUES (?, ?)');
const deleteSongFav         = db.prepare('DELETE FROM song_favorites WHERE user_id = ? AND song_id = ?');

// ── Playlist statements ──────────────────────────────────────────────────────
const plLikeCountStmt     = db.prepare('SELECT COUNT(*) AS c FROM playlist_likes WHERE playlist_id = ?');
const plFavCountStmt      = db.prepare('SELECT COUNT(*) AS c FROM playlist_favorites WHERE playlist_id = ?');
const plUserLikedStmt     = db.prepare('SELECT 1 FROM playlist_likes WHERE user_id = ? AND playlist_id = ?');
const plUserFavoritedStmt = db.prepare('SELECT 1 FROM playlist_favorites WHERE user_id = ? AND playlist_id = ?');
const insertPlLike        = db.prepare('INSERT OR IGNORE INTO playlist_likes (user_id, playlist_id) VALUES (?, ?)');
const deletePlLike        = db.prepare('DELETE FROM playlist_likes WHERE user_id = ? AND playlist_id = ?');
const insertPlFav         = db.prepare('INSERT OR IGNORE INTO playlist_favorites (user_id, playlist_id) VALUES (?, ?)');
const deletePlFav         = db.prepare('DELETE FROM playlist_favorites WHERE user_id = ? AND playlist_id = ?');

// ── Toggle functions ─────────────────────────────────────────────────────────
function toggleSongLike(userId, songId) {
  const exists = songUserLikedStmt.get(userId, songId);
  if (exists) {
    deleteSongLike.run(userId, songId);
  } else {
    insertSongLike.run(userId, songId);
    const song = songOwnerStmt.get(songId);
    if (song) notifications.create({ userId: song.uploaded_by, actorId: userId, actorName: getActorName(userId), action: 'like', entityType: 'song', entityId: songId, entityTitle: song.title, entitySlug: song.slug });
  }
  return { liked: !exists, count: songLikeCountStmt.get(songId).c };
}

function toggleSongFavorite(userId, songId) {
  const exists = songUserFavoritedStmt.get(userId, songId);
  if (exists) {
    deleteSongFav.run(userId, songId);
  } else {
    insertSongFav.run(userId, songId);
    const song = songOwnerStmt.get(songId);
    if (song) notifications.create({ userId: song.uploaded_by, actorId: userId, actorName: getActorName(userId), action: 'favorite', entityType: 'song', entityId: songId, entityTitle: song.title, entitySlug: song.slug });
  }
  return { favorited: !exists, count: songFavCountStmt.get(songId).c };
}

function togglePlaylistLike(userId, playlistId) {
  const exists = plUserLikedStmt.get(userId, playlistId);
  if (exists) {
    deletePlLike.run(userId, playlistId);
  } else {
    insertPlLike.run(userId, playlistId);
    const pl = playlistOwnerStmt.get(playlistId);
    if (pl) notifications.create({ userId: pl.created_by, actorId: userId, actorName: getActorName(userId), action: 'like', entityType: 'playlist', entityId: playlistId, entityTitle: pl.title, entitySlug: pl.slug });
  }
  return { liked: !exists, count: plLikeCountStmt.get(playlistId).c };
}

function togglePlaylistFavorite(userId, playlistId) {
  const exists = plUserFavoritedStmt.get(userId, playlistId);
  if (exists) {
    deletePlFav.run(userId, playlistId);
  } else {
    insertPlFav.run(userId, playlistId);
    const pl = playlistOwnerStmt.get(playlistId);
    if (pl) notifications.create({ userId: pl.created_by, actorId: userId, actorName: getActorName(userId), action: 'favorite', entityType: 'playlist', entityId: playlistId, entityTitle: pl.title, entitySlug: pl.slug });
  }
  return { favorited: !exists, count: plFavCountStmt.get(playlistId).c };
}

// ── Enrichment helpers ───────────────────────────────────────────────────────
// Mutates each item in-place, adding likeCount/favoriteCount/userLiked/userFavorited.
function enrichSongs(songs, userId = null) {
  for (const s of songs) {
    s.likeCount     = songLikeCountStmt.get(s.id).c;
    s.favoriteCount = songFavCountStmt.get(s.id).c;
    s.userLiked     = userId ? !!songUserLikedStmt.get(userId, s.id) : false;
    s.userFavorited = userId ? !!songUserFavoritedStmt.get(userId, s.id) : false;
  }
  return songs;
}

function enrichPlaylists(playlists, userId = null) {
  for (const p of playlists) {
    p.likeCount     = plLikeCountStmt.get(p.id).c;
    p.favoriteCount = plFavCountStmt.get(p.id).c;
    p.userLiked     = userId ? !!plUserLikedStmt.get(userId, p.id) : false;
    p.userFavorited = userId ? !!plUserFavoritedStmt.get(userId, p.id) : false;
  }
  return playlists;
}

// ── Profile liked/favorited queries ─────────────────────────────────────────
const likedSongsGuestStmt = db.prepare(`
  SELECT s.* FROM song_likes sl
  JOIN songs s ON s.id = sl.song_id
  WHERE sl.user_id = ? AND s.visibility = 'public'
  ORDER BY sl.created_at DESC
`);
const likedSongsUserStmt = db.prepare(`
  SELECT s.* FROM song_likes sl
  JOIN songs s ON s.id = sl.song_id
  WHERE sl.user_id = ? AND s.visibility IN ('public', 'logged_in')
  ORDER BY sl.created_at DESC
`);
const likedSongsVipStmt = db.prepare(`
  SELECT s.* FROM song_likes sl
  JOIN songs s ON s.id = sl.song_id
  WHERE sl.user_id = ? AND s.visibility IN ('public', 'logged_in', 'vip')
  ORDER BY sl.created_at DESC
`);
const likedPlaylistsGuestStmt = db.prepare(`
  SELECT p.* FROM playlist_likes pl
  JOIN playlists p ON p.id = pl.playlist_id
  WHERE pl.user_id = ? AND p.visibility = 'public'
    AND NOT EXISTS (
      SELECT 1 FROM playlist_songs ps
      JOIN songs s ON s.id = ps.song_id
      WHERE ps.playlist_id = p.id AND s.visibility IN ('logged_in', 'vip', 'private')
    )
  ORDER BY pl.created_at DESC
`);
const likedPlaylistsUserStmt = db.prepare(`
  SELECT p.* FROM playlist_likes pl
  JOIN playlists p ON p.id = pl.playlist_id
  WHERE pl.user_id = ? AND p.visibility IN ('public', 'logged_in')
    AND NOT EXISTS (
      SELECT 1 FROM playlist_songs ps
      JOIN songs s ON s.id = ps.song_id
      WHERE ps.playlist_id = p.id AND s.visibility IN ('vip', 'private')
    )
  ORDER BY pl.created_at DESC
`);
const likedPlaylistsVipStmt = db.prepare(`
  SELECT p.* FROM playlist_likes pl
  JOIN playlists p ON p.id = pl.playlist_id
  WHERE pl.user_id = ? AND p.visibility IN ('public', 'logged_in', 'vip')
    AND NOT EXISTS (
      SELECT 1 FROM playlist_songs ps
      JOIN songs s ON s.id = ps.song_id
      WHERE ps.playlist_id = p.id AND s.visibility = 'private'
    )
  ORDER BY pl.created_at DESC
`);

function getLikedSongs(userId, loggedIn = false, isVip = false) {
  return (isVip ? likedSongsVipStmt : loggedIn ? likedSongsUserStmt : likedSongsGuestStmt).all(userId);
}

function getLikedPlaylists(userId, loggedIn = false, isVip = false) {
  return (isVip ? likedPlaylistsVipStmt : loggedIn ? likedPlaylistsUserStmt : likedPlaylistsGuestStmt).all(userId);
}

// Site-wide recently liked songs (distinct songs, ordered by most recent like from any user).
const recentlyLikedGuestStmt = db.prepare(`
  SELECT s.* FROM songs s
  WHERE s.visibility = 'public'
    AND EXISTS (SELECT 1 FROM song_likes sl WHERE sl.song_id = s.id)
  ORDER BY (SELECT MAX(sl2.created_at) FROM song_likes sl2 WHERE sl2.song_id = s.id) DESC
  LIMIT ?
`);
const recentlyLikedUserStmt = db.prepare(`
  SELECT s.* FROM songs s
  WHERE s.visibility IN ('public', 'logged_in')
    AND EXISTS (SELECT 1 FROM song_likes sl WHERE sl.song_id = s.id)
  ORDER BY (SELECT MAX(sl2.created_at) FROM song_likes sl2 WHERE sl2.song_id = s.id) DESC
  LIMIT ?
`);
const recentlyLikedVipStmt = db.prepare(`
  SELECT s.* FROM songs s
  WHERE s.visibility IN ('public', 'logged_in', 'vip')
    AND EXISTS (SELECT 1 FROM song_likes sl WHERE sl.song_id = s.id)
  ORDER BY (SELECT MAX(sl2.created_at) FROM song_likes sl2 WHERE sl2.song_id = s.id) DESC
  LIMIT ?
`);

function getRecentlyLikedSongs(n = 5, loggedIn = false, isVip = false) {
  return (isVip ? recentlyLikedVipStmt : loggedIn ? recentlyLikedUserStmt : recentlyLikedGuestStmt).all(n);
}

// ── Most popular songs (scored by likes + 2×favorites) ───────────────────────
const mostPopularGuestStmt = db.prepare(`
  SELECT s.*,
    (COUNT(DISTINCT sl.user_id) + 2 * COUNT(DISTINCT sf.user_id)) AS score
  FROM songs s
  LEFT JOIN song_likes sl ON sl.song_id = s.id
  LEFT JOIN song_favorites sf ON sf.song_id = s.id
  WHERE s.visibility = 'public'
  GROUP BY s.id
  HAVING score > 0
  ORDER BY score DESC, s.created_at DESC
  LIMIT ?
`);
const mostPopularUserStmt = db.prepare(`
  SELECT s.*,
    (COUNT(DISTINCT sl.user_id) + 2 * COUNT(DISTINCT sf.user_id)) AS score
  FROM songs s
  LEFT JOIN song_likes sl ON sl.song_id = s.id
  LEFT JOIN song_favorites sf ON sf.song_id = s.id
  WHERE s.visibility IN ('public', 'logged_in')
  GROUP BY s.id
  HAVING score > 0
  ORDER BY score DESC, s.created_at DESC
  LIMIT ?
`);
const mostPopularVipStmt = db.prepare(`
  SELECT s.*,
    (COUNT(DISTINCT sl.user_id) + 2 * COUNT(DISTINCT sf.user_id)) AS score
  FROM songs s
  LEFT JOIN song_likes sl ON sl.song_id = s.id
  LEFT JOIN song_favorites sf ON sf.song_id = s.id
  WHERE s.visibility IN ('public', 'logged_in', 'vip')
  GROUP BY s.id
  HAVING score > 0
  ORDER BY score DESC, s.created_at DESC
  LIMIT ?
`);

function getMostPopular(n = 20, loggedIn = false, isVip = false) {
  return (isVip ? mostPopularVipStmt : loggedIn ? mostPopularUserStmt : mostPopularGuestStmt).all(n);
}

module.exports = {
  toggleSongLike, toggleSongFavorite,
  togglePlaylistLike, togglePlaylistFavorite,
  enrichSongs, enrichPlaylists,
  getLikedSongs, getLikedPlaylists,
  getRecentlyLikedSongs, getMostPopular,
};