/**
 * NovaSonic Backend Server
 * Downloads music via yt-dlp and saves directly into your Navidrome music library
 *
 * Requirements:
 *   - Node.js 18+
 *   - yt-dlp installed (https://github.com/yt-dlp/yt-dlp)
 *   - ffmpeg installed
 */

const express = require('express');
const { spawn, execSync } = require('child_process');
const path    = require('path');
const fs      = require('fs');
const https   = require('https');

// ─── CONFIG ───────────────────────────────────────────────────────────────────
const CONFIG = {
  port:         process.env.PORT            || 3700,
  musicPath:    process.env.MUSIC_PATH      || '/music',
  ytdlpBin:     process.env.YTDLP_BIN      || 'yt-dlp',
  audioFmt:     process.env.AUDIO_FMT      || 'mp3',
  audioQuality: process.env.AUDIO_QUALITY  || '0',
  maxParallel:  parseInt(process.env.MAX_PARALLEL || '2'),
};

// ─── INIT ─────────────────────────────────────────────────────────────────────
const app = express();
app.use((req, res, next) => {
  res.setHeader('Access-Control-Allow-Origin', '*');
  res.setHeader('Access-Control-Allow-Methods', 'GET,POST,OPTIONS');
  res.setHeader('Access-Control-Allow-Headers', 'Content-Type,Authorization');
  res.setHeader('Access-Control-Allow-Private-Network', 'true');
  if (req.method === 'OPTIONS') { res.sendStatus(204); return; }
  next();
});
app.use(express.json());

const jobs = new Map();

let ytdlpVersion = 'unknown';
try {
  ytdlpVersion = execSync(`${CONFIG.ytdlpBin} --version`, { timeout: 5000 }).toString().trim();
  console.log(`✅ yt-dlp ${ytdlpVersion} found`);
} catch {
  console.warn('⚠️  yt-dlp not found!');
}

if (!fs.existsSync(CONFIG.musicPath)) {
  console.warn(`⚠️  Music path "${CONFIG.musicPath}" does not exist — creating it`);
  fs.mkdirSync(CONFIG.musicPath, { recursive: true });
}

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

// Convert "Artist feat. B" / "Artist ft. B" / "Artist featuring B" → "Artist / B"
// so Navidrome splits on "/" and lists each as a separate artist
function navidromeArtist(name) {
  if (!name) return name;
  return name
    .replace(/\s+feat\.?\s+/gi, ' / ')
    .replace(/\s+ft\.?\s+/gi, ' / ')
    .replace(/\s+featuring\s+/gi, ' / ');
}

function updateJob(id, update) {
  const job = jobs.get(id);
  if (job) jobs.set(id, { ...job, ...update, updatedAt: Date.now() });
}

function log(jobId, msg) {
  const j = jobs.get(jobId);
  if (j) jobs.set(jobId, { ...j, log: [...(j.log || []), msg], message: msg });
  console.log(`[${jobId}] ${msg}`);
}

// 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');
  // Upgrade to 1000x1000 — iTunes URL pattern: ...100x100bb.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) {
  return AUDIO_EXTS
    .map(ext => path.join(dir, `${trackPrefix}${safeTitle}.${ext}`))
    .find(f => fs.existsSync(f)) || null;
}

// Download a single track: yt-dlp audio + ffmpeg clean metadata + iTunes cover embedded
async function downloadTrack({ jobId, artist, albumArtist, title, album, year, trackNum, totalTracks, discNum, discTotal, compilation, genre, artworkUrl, outputDir }) {
  const mainArtist = albumArtist || artist;
  const safeArtist = sanitize(mainArtist);
  const safeAlbum  = sanitize(album || 'Singles');
  const dir = path.join(outputDir || CONFIG.musicPath, safeArtist, safeAlbum);
  fs.mkdirSync(dir, { recursive: true });

  const safeTitle   = sanitize(title);
  const trackPrefix = trackNum ? String(trackNum).padStart(2, '0') + ' - ' : '';

  const existing = findExistingTrack(dir, trackPrefix, safeTitle);
  if (existing) {
    log(jobId, `⏭ Bereits vorhanden: ${path.basename(existing)} — übersprungen`);
    return { success: true, dir, skipped: true };
  }

  const outputTemplate = path.join(dir, `${trackPrefix}${safeTitle}.%(ext)s`);
  const query          = `${mainArtist} - ${title} official audio`;
  log(jobId, `🔍 Suche: "${query}"`);

  // Step 1: yt-dlp — audio only, no thumbnail (we embed iTunes artwork ourselves)
  await new Promise((resolve, reject) => {
    const args = [
      `ytsearch1:${query}`,
      '--extract-audio',
      '--audio-format',   CONFIG.audioFmt,
      '--audio-quality',  CONFIG.audioQuality,
      '-o',               outputTemplate,
      '--no-playlist',
      '--playlist-items', '1',
      '--no-warnings',
      '--newline',
    ];
    const proc = spawn(CONFIG.ytdlpBin, args, { env: { ...process.env, PYTHONUNBUFFERED: '1' } });
    let stderr = '', lastPct = '';
    proc.stdout.on('data', d => {
      d.toString().split('\n').filter(l => l.trim()).forEach(line => {
        if (line.includes('%') && line === lastPct) return;
        if (line.includes('%')) lastPct = line;
        log(jobId, line.trim());
      });
    });
    proc.stderr.on('data', d => {
      stderr += d.toString();
      d.toString().split('\n')
        .filter(l => l.trim() && !l.startsWith('[debug]'))
        .forEach(l => log(jobId, l.trim()));
    });
    proc.on('error', reject);
    proc.on('close', code =>
      code === 0 ? resolve() : reject(new Error(`yt-dlp code ${code}: ${stderr.slice(-300)}`))
    );
  });

  // Step 2: find the audio file yt-dlp wrote (newest audio file in dir)
  const audioFile = fs.readdirSync(dir)
    .filter(f => AUDIO_EXTS.some(e => f.endsWith(`.${e}`)))
    .map(f => path.join(dir, f))
    .sort((a, b) => fs.statSync(b).mtimeMs - fs.statSync(a).mtimeMs)[0];

  if (!audioFile) {
    log(jobId, '⚠️  Keine Audio-Datei gefunden');
    return { success: true, dir };
  }

  // Step 3: download hi-res iTunes artwork
  const coverPath = await downloadArtwork(artworkUrl, dir);
  const hasCover  = !!(coverPath && fs.existsSync(coverPath));

  log(jobId, `🏷  Metadaten + Cover → ${path.basename(audioFile)}`);

  // Step 4: ffmpeg — strip old tags, write clean ID3, embed hi-res artwork
  const fileExt = path.extname(audioFile);
  const tmpFile = audioFile.slice(0, -fileExt.length) + '.metatmp' + fileExt;
  await new Promise(resolve => {
    const ffArgs = ['-i', audioFile];
    if (hasCover) ffArgs.push('-i', coverPath);

    // Map: audio from input 0, artwork from input 1 (if available)
    ffArgs.push('-map', '0:a');
    if (hasCover) ffArgs.push('-map', '1:v');

    ffArgs.push(
      '-c',             'copy',
      '-map_metadata',  '-1',         // strip all existing tags (removes blurry YT thumbnail)
      '-id3v2_version', '3',
      '-metadata', `title=${title}`,
      '-metadata', `artist=${navidromeArtist(artist)}`,
      '-metadata', `album_artist=${mainArtist}`,
    );
    if (album)       ffArgs.push('-metadata', `album=${album}`);
    if (year)        ffArgs.push('-metadata', `date=${String(year)}`);
    if (trackNum)    ffArgs.push('-metadata', `track=${totalTracks ? `${trackNum}/${totalTracks}` : String(trackNum)}`);
    if (totalTracks) ffArgs.push('-metadata', `totaltracks=${String(totalTracks)}`);
    if (genre)         ffArgs.push('-metadata', `genre=${genre}`);
    if (discNum)       ffArgs.push('-metadata', `disc=${discTotal ? `${discNum}/${discTotal}` : String(discNum)}`);
    if (compilation)   ffArgs.push('-metadata', `compilation=1`);
    if (hasCover) {
      ffArgs.push(
        '-metadata:s:v', 'title=Album cover',
        '-metadata:s:v', 'comment=Cover (front)',
      );
    }
    ffArgs.push(tmpFile, '-y');

    const ff = spawn('ffmpeg', ffArgs);
    let ffErr = '';
    ff.stderr.on('data', d => ffErr += d.toString());
    ff.on('error', () => resolve());
    ff.on('close', code => {
      if (code === 0 && fs.existsSync(tmpFile)) {
        fs.renameSync(tmpFile, audioFile);
        log(jobId, `✅ Fertig${hasCover ? ' (Cover 1000x1000 eingebettet)' : ''}`);
      } else {
        try { fs.unlinkSync(tmpFile); } catch {}
        log(jobId, `⚠️  ffmpeg code ${code}`);
        if (ffErr) log(jobId, ffErr.slice(-200));
      }
      resolve();
    });
  });

  return { success: true, dir };
}

// Download all tracks of an album sequentially
async function downloadAlbumTracks({ jobId, artist, albumTitle, tracks, artworkUrl }) {
  const total = tracks.length;
  log(jobId, `📀 Album "${albumTitle}" — ${total} Tracks`);
  let done = 0;

  for (const track of tracks) {
    try {
      await downloadTrack({
        jobId,
        artist:      track.artistName  || artist,  // track artist (may include feat.)
        albumArtist: artist,                        // always the main artist → consistent grouping
        title:       track.trackName   || track.title,
        album:       albumTitle,
        year:        track.releaseDate ? new Date(track.releaseDate).getFullYear() : undefined,
        trackNum:    track.trackNumber     || undefined,
        totalTracks: total,
        discNum:     track.discNumber      || undefined,
        discTotal:   track.discCount       || undefined,
        compilation: track.collectionType === 'Compilation' || undefined,
        genre:       track.primaryGenreName || undefined,
        artworkUrl:  artworkUrl || track.artworkUrl100,
        outputDir:   CONFIG.musicPath,
      });
      done++;
      updateJob(jobId, { progress: Math.round((done / total) * 90) });
    } catch (e) {
      log(jobId, `⚠️  Fehler bei "${track.trackName || track.title}": ${e.message}`);
    }
  }
}

// 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=de`, 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([]));
  });
}

// 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`;
    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);
  });
}

// ─── QUEUE ────────────────────────────────────────────────────────────────────
let activeDownloads = 0;
const downloadQueue = [];

function processQueue() {
  if (activeDownloads >= CONFIG.maxParallel || downloadQueue.length === 0) return;
  const task = downloadQueue.shift();
  activeDownloads++;
  task().finally(() => { activeDownloads--; processQueue(); });
}

function enqueue(task) {
  downloadQueue.push(task);
  processQueue();
}

// ─── ROUTES ──────────────────────────────────────────────────────────────────

app.get('/api/health', (req, res) => {
  res.json({ status: 'ok', ytdlpVersion, musicPath: CONFIG.musicPath, audioFormat: CONFIG.audioFmt, activeJobs: activeDownloads, queueLength: downloadQueue.length });
});

app.post('/api/download', async (req, res) => {
  const { type, artist, title, album, artworkUrl, collectionId, jobId: clientJobId } = req.body;
  if (!artist || !title) return res.status(400).json({ error: 'artist and title required' });

  const jobId = clientJobId || ('job_' + Date.now());
  jobs.set(jobId, {
    id: jobId, type, artist, title, album,
    status: 'queued', progress: 0, message: 'In Warteschlange…',
    log: [], createdAt: Date.now(), updatedAt: Date.now(),
  });
  res.json({ jobId, status: 'queued' });

  enqueue(async () => {
    updateJob(jobId, { status: 'running', progress: 5, message: 'Gestartet…' });
    try {
      if (type === 'track') {
        await downloadTrack({ jobId, artist, title, album, artworkUrl });
        updateJob(jobId, { status: 'done', progress: 100, message: 'Fertig!' });

      } else if (type === 'album') {
        let tracks = [];
        if (collectionId) {
          log(jobId, '📋 Lade Track-Liste von iTunes…');
          tracks = await fetchItunesTracks(collectionId);
        }
        if (!tracks.length) {
          log(jobId, '🔍 Suche Album auf iTunes…');
          tracks = await searchItunesAlbumTracks(artist, album || title);
        }
        if (!tracks.length) {
          throw new Error(`Keine einzelnen Tracks für "${album || title}" gefunden. Bitte über iTunes Global-Suche herunterladen.`);
        }
        await downloadAlbumTracks({ jobId, artist, albumTitle: album || title, tracks, artworkUrl });
        updateJob(jobId, { status: 'done', progress: 100, message: `Album "${album || title}" fertig!` });

      } else if (type === 'artist') {
        log(jobId, `🎤 Künstler-Download: ${artist}`);
        const artistData = await new Promise((resolve, reject) => {
          https.get(`https://itunes.apple.com/search?term=${encodeURIComponent(artist)}&media=music&entity=album&limit=10&country=de`, 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 artistAlbums = artistData.filter(a => a.artistName?.toLowerCase() === artist.toLowerCase()).slice(0, 10);
        log(jobId, `📀 ${artistAlbums.length} Alben gefunden`);
        let done = 0;
        for (const alb of artistAlbums) {
          const tracks = await fetchItunesTracks(alb.collectionId).catch(() => []);
          if (tracks.length) {
            await downloadAlbumTracks({ jobId, artist, albumTitle: alb.collectionName, tracks, artworkUrl: alb.artworkUrl100 });
          }
          done++;
          updateJob(jobId, { progress: Math.round((done / artistAlbums.length) * 95) });
        }
        updateJob(jobId, { status: 'done', progress: 100, message: `Künstler "${artist}" fertig!` });
      }
    } catch (err) {
      console.error(`[${jobId}] Error:`, err.message);
      updateJob(jobId, { status: 'error', message: err.message });
    }
  });
});

app.get('/api/status/:jobId', (req, res) => {
  const job = jobs.get(req.params.jobId);
  if (!job) return res.status(404).json({ error: 'Job not found' });
  res.json(job);
});

app.get('/api/jobs', (req, res) => {
  res.json(Array.from(jobs.values()).sort((a, b) => b.createdAt - a.createdAt).slice(0, 50));
});

// ─── START ────────────────────────────────────────────────────────────────────
app.listen(CONFIG.port, () => {
  console.log(`\n🎵 NovaSonic Backend running on port ${CONFIG.port}`);
  console.log(`   Music folder : ${CONFIG.musicPath}`);
  console.log(`   Audio format : ${CONFIG.audioFmt} (quality ${CONFIG.audioQuality})`);
  console.log(`   yt-dlp       : ${ytdlpVersion}`);
  console.log('');
});