NovaSonic/backend/lib/deezer.js

const https = require('https');

// ─── DEEZER METADATA SOURCE ───────────────────────────────────────────────────
// Apple's iTunes /search returns 403 from server/datacenter IPs, so all server-side
// metadata (single-track enrichment, album track lists, artist discography, the
// metadata-editor autofill) comes from Deezer. Free, no key, ~50 req/5s, returns
// explicit flags + artist images + durations. Results are mapped to the same
// "ItunesItem" shape the download pipeline (downloadAlbumTracks / downloadTrack)
// already consumes, so nothing downstream had to change.

const DZ = 'https://api.deezer.com';

function dzGet(subpath) {
  return new Promise((resolve, reject) => {
    https.get(`${DZ}/${subpath}`, { headers: { 'User-Agent': 'NovaSonic/1.0' } }, res => {
      let d = '';
      res.on('data', c => d += c);
      res.on('end', () => { try { resolve(JSON.parse(d) || {}); } catch { reject(new Error('Deezer parse error')); } });
    }).on('error', reject);
  });
}

// ─── matching helpers (local copies to avoid a circular require with metadata.js) ─
function normalizeTitle(s) {
  return (s || '')
    .toLowerCase().trim()
    .replace(/\s+-\s+([^-]+)$/, ' ($1)')
    .replace(/[\[(（][^\]）)]*[\]）)]/g, '')
    .replace(/[,.'!?]/g, '')
    .replace(/\s+/g, ' ')
    .trim();
}
const stripLeadSym = s => (s || '').replace(/^[^\p{L}\p{N}]+/u, '').trim();
const firstWord = s => stripLeadSym((s || '').toLowerCase()).split(/[\s,;/]/)[0];
const yearOf = d => { const y = d ? new Date(d).getFullYear() : NaN; return Number.isFinite(y) ? y : undefined; };
// Deezer covers come in fixed sizes; cover_xl is 1000x1000 (matches the iTunes hi-res artwork).
const coverXl = a => a?.cover_xl || a?.cover_big || a?.cover_medium || a?.cover || '';

// Map one album track (from /album/{id} .tracks.data — these carry no track_position,
// so the album's own ordering supplies the number) to the iTunes track shape.
function mapAlbumTrack(t, al, index) {
  return {
    wrapperType:         'track',
    trackId:             t.id,
    trackName:           t.title,
    artistName:          t.artist?.name || al.artist?.name || '',   // per-track artist (mixed albums)
    collectionName:      al.title,
    collectionArtistName: al.artist?.name || '',                    // album-level artist (stable)
    collectionType:      al.record_type === 'compilation' ? 'Compilation' : 'Album',
    artworkUrl100:       coverXl(al),
    releaseDate:         al.release_date || undefined,
    primaryGenreName:    al.genres?.data?.[0]?.name || undefined,
    trackNumber:         index + 1,
    trackCount:          al.nb_tracks || undefined,
    trackTimeMillis:     t.duration ? t.duration * 1000 : undefined,
    trackExplicitness:   t.explicit_lyrics ? 'explicit' : 'notExplicit',
    previewUrl:          t.preview || '',
  };
}

// Pick the best track from a Deezer /search result list for (artist, title). Pure + exported
// so the matching rules are unit-testable. Strict = same title AND same first artist word;
// falls back to a title-only match, but never for Japanese titles (same title, different artist
// is common for anime/OST). Returns the matched Deezer track or null.
function pickTrackMatch(results, artist, title) {
  if (!Array.isArray(results) || !results.length) return null;
  const normT = normalizeTitle(title);
  const normA = stripLeadSym((artist || '').split(/[;,&]/)[0].trim()).toLowerCase().trim();
  const strict    = results.find(t => normalizeTitle(t.title) === normT && firstWord(t.artist?.name) === firstWord(normA));
  const JP_RE     = /[぀-ヿ㐀-䶿一-鿿]/;
  const isJp      = JP_RE.test(normT) || JP_RE.test(normA);
  const titleOnly = results.find(t => normalizeTitle(t.title) === normT);
  return strict || (!isJp ? titleOnly || null : null);
}

// Single-track metadata — the Deezer equivalent of the old iTunes lookupTrackMeta.
// Fills album/year/trackNum/genre/duration/artwork when the caller only has artist+title.
// Returns {} when nothing convincing matches (callers treat that as "no enrichment").
async function lookupTrackMeta(artist, title) {
  try {
    const baseTitle    = title.replace(/\s*[-–]\s*\S[^-]*$/, '').trim() || title;
    const searchTitle  = baseTitle !== title ? baseTitle : title;
    const searchArtist = stripLeadSym((artist || '').split(/[;,&]/)[0].trim());
    const q = encodeURIComponent(`${searchArtist} ${searchTitle}`);
    const results = (await dzGet(`search?q=${q}&limit=10`)).data || [];
    if (!results.length) return {};

    const match = pickTrackMatch(results, artist, title);
    if (!match) return {};

    // The search result lacks genre / track number / release date — the album endpoint carries them.
    const al = match.album?.id ? await dzGet(`album/${match.album.id}`).catch(() => ({})) : {};
    // track_position + disk_number live on the full /track record, not on the search hit.
    const tr = match.id ? await dzGet(`track/${match.id}`).catch(() => ({})) : {};

    return {
      album:            match.album?.title || al.title || '',
      albumArtist:      al.artist?.name || undefined,
      trackName:        match.title || undefined,
      year:             yearOf(tr.release_date || al.release_date),
      trackNum:         tr.track_position || undefined,
      totalTracks:      al.nb_tracks || undefined,
      discNum:          tr.disk_number || undefined,
      discTotal:        undefined,
      genre:            al.genres?.data?.[0]?.name || undefined,
      artworkUrl:       coverXl(al) || coverXl(match.album) || '',
      durationMs:       (tr.duration || match.duration) ? (tr.duration || match.duration) * 1000 : undefined,
      metaArtistName:   match.artist?.name || undefined,
    };
  } catch { return {}; }
}

// All tracks of a Deezer album id, in the legacy ItunesItem track shape.
async function fetchAlbumTracks(albumId) {
  try {
    const al = await dzGet(`album/${albumId}`);
    return (al.tracks?.data || []).map((t, i) => mapAlbumTrack(t, al, i));
  } catch { return []; }
}

// Album fallback when no album id is known: search Deezer for the album, then its tracks.
async function searchAlbumTracks(artist, album) {
  try {
    const q = encodeURIComponent(`${artist} ${album}`);
    const results = (await dzGet(`search/album?q=${q}&limit=5`)).data || [];
    const lc = s => (s || '').toLowerCase();
    const match = results.find(r =>
      lc(r.title).includes(lc(album)) || lc(r.artist?.name).includes(lc(artist))
    ) || results[0];
    return match ? await fetchAlbumTracks(match.id) : [];
  } catch { return []; }
}

// Artist discography for the artist-download: search the artist, take real albums
// (record_type "album", not singles/EPs), return {collectionId, collectionName, artworkUrl100}.
async function fetchArtistAlbums(artistName, limit = 10) {
  try {
    const artists = (await dzGet(`search/artist?q=${encodeURIComponent(artistName)}&limit=1`)).data || [];
    if (!artists.length) return [];
    const albums = (await dzGet(`artist/${artists[0].id}/albums?limit=100`)).data || [];
    return albums
      .filter(a => a.record_type === 'album')
      .slice(0, limit)
      .map(a => ({
        collectionId:   a.id,
        collectionName: a.title,
        artistName:     artists[0].name,
        artworkUrl100:  coverXl(a),
      }));
  } catch { return []; }
}

module.exports = {
  dzGet,
  lookupTrackMeta,
  fetchAlbumTracks,
  searchAlbumTracks,
  fetchArtistAlbums,
  // exported for unit tests
  mapAlbumTrack,
  pickTrackMatch,
  normalizeTitle,
};