NovaSonic/backend/lib/metadata.js

const https = require('https');
const path  = require('path');
const fs    = require('fs');

function sanitize(s) {
  return (s || 'Unknown').replace(/[\\/:*?"<>|]/g, '_').trim().slice(0, 100);
}

function navidromeArtist(name) {
  if (!name) return name;
  return name
    .replace(/\s+feat\.?\s+/gi, ';')
    .replace(/\s+ft\.?\s+/gi, ';')
    .replace(/\s+featuring\s+/gi, ';')
    .replace(/\s+&\s+/g, ';')

    .replace(/,\s*/g, ';');
}

// Download hi-res iTunes artwork (1000x1000) to cover.jpg, return path or null
async function downloadArtwork(url, dir) {
  if (!url) return null;
  const dest  = path.join(dir, 'cover.jpg');
  const hiRes = url.replace(/\d+x\d+bb\./, '1000x1000bb.');
  return new Promise(resolve => {
    const tryUrl = (u, fallback) => {
      const file = fs.createWriteStream(dest);
      https.get(u, res => {
        if (res.statusCode !== 200) {
          res.resume();
          file.close();
          try { fs.unlinkSync(dest); } catch {}
          if (fallback) tryUrl(fallback, null);
          else resolve(null);
          return;
        }
        res.pipe(file);
        file.on('finish', () => resolve(dest));
        file.on('error',  () => resolve(null));
      }).on('error', () => {
        if (fallback) tryUrl(fallback, null);
        else resolve(null);
      });
    };
    tryUrl(hiRes, url !== hiRes ? url : null);
  });
}

const AUDIO_EXTS = ['mp3', 'flac', 'opus', 'm4a', 'ogg', 'wav'];

function findExistingTrack(dir, trackPrefix, safeTitle, safeArtist) {
  // Check new format "{prefix}{artist} - {title}.ext" first, then old format "{prefix}{title}.ext"
  const names = safeArtist
    ? [`${trackPrefix}${safeArtist} - ${safeTitle}`, `${trackPrefix}${safeTitle}`]
    : [`${trackPrefix}${safeTitle}`];
  return AUDIO_EXTS.flatMap(ext => names.map(n => path.join(dir, `${n}.${ext}`)))
    .find(f => fs.existsSync(f)) || null;
}

// Fetch plain + synced lyrics from LRCLIB
async function fetchLyrics(artist, title, album) {
  try {
    const p = new URLSearchParams({ artist_name: artist, track_name: title });
    if (album) p.set('album_name', album);
    const r = await fetch(`https://lrclib.net/api/get?${p}`, {
      headers: { 'User-Agent': 'NovaSonic/1.0' },
      signal: AbortSignal.timeout(8000),
    });
    if (!r.ok) return null;
    const d = await r.json();
    return { plain: d.plainLyrics || null, synced: d.syncedLyrics || null };
  } catch { return null; }
}

// Normalize a track title for comparison: unify variant suffixes so that
// "don't rush - slowed" and "don't rush (slowed)" are treated as equal.
function normalizeTitle(s) {
  return (s || '')
    .toLowerCase()
    .trim()
    // convert "title - variant" → "title (variant)" so both forms compare equal
    .replace(/\s+-\s+([^-]+)$/, ' ($1)')
    // strip all remaining parens/brackets content for the base comparison
    .replace(/[\[(（][^\]）)]*[\]）)]/g, '')
    .trim();
}

// iTunes track lookup — fills in album, year, trackNum, totalTracks, genre when missing
async function lookupItunesTrackMeta(artist, title) {
  try {
    // Search with base title (strip variant suffix) for better iTunes hit rate —
    // e.g. "don't rush - slowed" → search "don't rush" so iTunes finds the single
    const baseTitle = title.replace(/\s*[-–]\s*\S[^-]*$/, '').trim() || title;
    const searchTitle = baseTitle !== title ? baseTitle : title;
    const url = `https://itunes.apple.com/search?term=${encodeURIComponent(artist + ' ' + searchTitle)}&media=music&entity=musicTrack&limit=10&country=us&explicit=Yes`;
    const results = await new Promise((resolve, reject) => {
      https.get(url, res => {
        let d = ''; res.on('data', c => d += c);
        res.on('end', () => { try { resolve(JSON.parse(d).results || []); } catch { reject(new Error('parse')); } });
      }).on('error', reject);
    });
    const normT     = normalizeTitle(title);
    const normA     = (artist || '').toLowerCase().trim();
    // Split by space OR comma/semicolon/slash so "VXLLAIN, iGRES" → "vxllain" not "vxllain,"
    const firstWord = s => (s || '').toLowerCase().split(/[\s,;/]/)[0];
    // Prefer strict match (title + first-word artist), fall back to title-only.
    // Title-only fallback handles cases where kuromoji gave a wrong artist romanization
    // (e.g. "Terui Jun Sei" vs iTunes "Yoshimasa Terui" — different first word).
    const match = results.find(t =>
      normalizeTitle(t.trackName) === normT &&
      firstWord(t.artistName) === firstWord(normA)
    ) || results.find(t => normalizeTitle(t.trackName) === normT);
    if (!match) return {};
    return {
      album:            match.collectionName || '',
      year:             match.releaseDate ? new Date(match.releaseDate).getFullYear() : undefined,
      trackNum:         match.trackNumber   || undefined,
      totalTracks:      match.trackCount    || undefined,
      discNum:          match.discNumber    || undefined,
      discTotal:        match.discCount     || undefined,
      genre:            match.primaryGenreName || undefined,
      artworkUrl:       (match.artworkUrl100 || '').replace('100x100bb', '1000x1000bb'),
      durationMs:       match.trackTimeMillis  || undefined,
      itunesArtistName: match.artistName       || undefined,
    };
  } catch { return {}; }
}

// Fetch individual tracks for an iTunes collectionId
async function fetchItunesTracks(collectionId) {
  return new Promise((resolve, reject) => {
    const url = `https://itunes.apple.com/lookup?id=${collectionId}&entity=song&explicit=Yes`;
    https.get(url, res => {
      let data = '';
      res.on('data', d => data += d);
      res.on('end', () => {
        try {
          const parsed = JSON.parse(data);
          resolve((parsed.results || []).filter(r => r.wrapperType === 'track'));
        } catch { reject(new Error('iTunes API parse error')); }
      });
    }).on('error', reject);
  });
}

// Search iTunes for album tracks by artist + album name (fallback when no collectionId)
async function searchItunesAlbumTracks(artist, album) {
  return new Promise(resolve => {
    const q = encodeURIComponent(`${artist} ${album}`);
    https.get(`https://itunes.apple.com/search?term=${q}&media=music&entity=album&limit=5&country=us&explicit=Yes`, res => {
      let d = '';
      res.on('data', c => d += c);
      res.on('end', () => {
        try {
          const results = JSON.parse(d).results || [];
          const match = results.find(r =>
            r.collectionName?.toLowerCase().includes(album.toLowerCase()) ||
            r.artistName?.toLowerCase().includes(artist.toLowerCase())
          );
          if (match) fetchItunesTracks(match.collectionId).then(resolve).catch(() => resolve([]));
          else resolve([]);
        } catch { resolve([]); }
      });
    }).on('error', () => resolve([]));
  });
}

module.exports = {
  sanitize, navidromeArtist,
  downloadArtwork, findExistingTrack,
  lookupItunesTrackMeta, fetchItunesTracks, searchItunesAlbumTracks,
};