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

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

const CONFIG    = require('./lib/config');
const { jobs, updateJob, log } = require('./lib/jobs');
const { lookupItunesTrackMeta, fetchItunesTracks, searchItunesAlbumTracks } = require('./lib/metadata');
const { downloadTrack, downloadAlbumTracks } = require('./lib/downloader');

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

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 });
}

// ─── 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();
}

// ─── SPOTIFY ──────────────────────────────────────────────────────────────────
function parseSpotifyUrl(url) {
  const m = url.match(/open\.spotify\.com\/(?:[a-z]{2,8}-[a-z]{2,8}\/)?(?:intl-[a-z-]+\/)?(track|album|playlist)\/([A-Za-z0-9]+)/);
  if (!m) throw new Error('Ungültige Spotify-URL — erwartet: open.spotify.com/track|album|playlist/...');
  return { type: m[1], id: m[2] };
}


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

app.post('/api/spotify/track-artwork', async (req, res) => {
  const tracks = req.body.tracks || [];
  if (!tracks.length) return res.json({ results: [] });
  const CONC = 8;
  const results = [];
  for (let i = 0; i < tracks.length; i += CONC) {
    const batch = tracks.slice(i, i + CONC);
    const batchRes = await Promise.all(batch.map(async t => {
      const searchArtist = (t.artistName || '').split(/\s*[,/•]\s*/)[0].trim();
      const meta = await lookupItunesTrackMeta(searchArtist, t.trackName || '');
      return { idx: t.idx, artworkUrl: meta.artworkUrl || t.existingArt || '' };
    }));
    results.push(...batchRes);
  }
  res.json({ results });
});

// ─── ITUNES PROXY ─────────────────────────────────────────────────────────────
// Browsers can't call itunes.apple.com directly (no CORS headers). Proxy it here.
app.get('/api/itunes/:endpoint', (req, res) => {
  const allowed = new Set(['search', 'lookup']);
  if (!allowed.has(req.params.endpoint)) return res.status(404).json({ error: 'not found' });
  const qs = new URLSearchParams(req.query).toString();
  const target = `https://itunes.apple.com/${req.params.endpoint}${qs ? '?' + qs : ''}`;
  https.get(target, { headers: { 'User-Agent': 'NovaSonic/1.0' } }, upstream => {
    res.setHeader('Content-Type', 'application/json');
    upstream.pipe(res);
  }).on('error', e => res.status(502).json({ error: e.message }));
});

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

async function _resolveSpotifyViaSpotdl(url) {
  const { execFile } = require('child_process');
  const scriptPath = path.join(__dirname, 'spotify_resolve.py');
  // Strip ?si= and other tracking params — spotdl doesn't handle them
  const cleanUrl = url.split('?')[0];
  return new Promise((resolve, reject) => {
    execFile('python3', [scriptPath, cleanUrl], { timeout: 90000, maxBuffer: 10 * 1024 * 1024 }, (err, stdout, stderr) => {
      if (stderr?.trim()) stderr.trim().split('\n').forEach(l => console.log('[py]', l));
      // Always try to parse stdout first — script outputs JSON even on error
      const out = stdout?.trim();
      if (out) {
        try {
          const data = JSON.parse(out);
          if (data.error === 'RATE_LIMITED') return reject(new Error(`RATE_LIMITED:${data.retryAfter || 30}`));
          if (data.error) return reject(new Error(`spotdl: ${data.error}`));
          return resolve(data);
        } catch { /* not JSON, fall through */ }
      }
      if (err) return reject(new Error(`spotdl exited ${err.code}: ${stderr?.trim() || out || err.message}`));
      reject(new Error(`spotdl: keine Ausgabe`));
    });
  });
}

// Tracks when the Spotify rate limit window expires so retries never reach Spotify.
let _spRateLimitUntil = 0;

app.post('/api/spotify/resolve', async (req, res) => {
  const { url } = req.body;
  if (!url) return res.status(400).json({ error: 'url required' });

  // Block retries until the cooldown the Spotify told us has actually elapsed.
  const now = Date.now();
  if (_spRateLimitUntil > now) {
    const secs = Math.ceil((_spRateLimitUntil - now) / 1000);
    console.log(`[spotify/resolve] cooldown active — ${secs}s remaining`);
    return res.status(429).json({ error: 'RATE_LIMITED', retryAfter: secs });
  }

  try {
    const { type, id } = parseSpotifyUrl(url);
    console.log(`[spotify/resolve] ${type} ${id}`);

    const timeout = new Promise((_, reject) =>
      setTimeout(() => reject(new Error('Zeitüberschreitung — Spotify API antwortet nicht (>120s)')), 120000)
    );
    const data = await Promise.race([_resolveSpotifyViaSpotdl(url), timeout]);
    res.json(data);
  } catch(e) {
    console.error('[spotify/resolve]', e.message);
    if (e.message.includes('403') && e.message.includes('/playlists/')) {
      return res.status(403).json({ error: 'EDITORIAL_PLAYLIST' });
    }
    if (e.message.startsWith('RATE_LIMITED:')) {
      const secs = parseInt(e.message.split(':')[1], 10) || 30;
      _spRateLimitUntil = Date.now() + secs * 1000;
      return res.status(429).json({ error: 'RATE_LIMITED', retryAfter: secs });
    }
    res.status(500).json({ error: e.message });
  }
});

app.post('/api/download', async (req, res) => {
  const { type, artist, title, album, artworkUrl, collectionId, jobId: clientJobId, explicit,
          trackNum: bodyTrackNum, totalTracks: bodyTotalTracks, discNum: bodyDiscNum, discTotal: bodyDiscTotal } = 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') {
        const sp     = req.body.tracks?.[0] || {};
        const spAlbum = sp.collectionName || album || '';
        const spArt   = sp.artworkUrl100  || artworkUrl || '';
        const spYear  = sp.releaseDate ? new Date(sp.releaseDate).getFullYear() : undefined;
        let meta = {
          album: spAlbum, year: spYear,
          trackNum:    sp.trackNumber  || bodyTrackNum    || undefined,
          totalTracks: sp.trackCount   || bodyTotalTracks || undefined,
          discNum:     sp.discNumber   || bodyDiscNum     || undefined,
          discTotal:   sp.discCount    || bodyDiscTotal   || undefined,
          artworkUrl: spArt, explicit: sp.trackExplicitness === 'explicit' || !!explicit,
          durationMs: sp.durationMs || undefined,
        };
        if (!meta.album) {
          const searchArtist = artist.split(',')[0].trim();
          log(jobId, '📋 Suche Album-Metadaten von iTunes…');
          const extra = await lookupItunesTrackMeta(searchArtist, title);
          if (extra.album) log(jobId, `📋 Album: "${extra.album}" (${extra.year || '?'})`);
          meta = { ...meta, ...extra, artworkUrl: spArt || extra.artworkUrl || '' };
        } else {
          log(jobId, `📋 Album aus Spotify: "${meta.album}"`);
        }
        const result = await downloadTrack({ jobId, artist, title, ...meta });
        if (result?.skipped) {
          updateJob(jobId, { status: 'done', progress: 100, message: 'Bereits vorhanden – übersprungen', skipped: true });
        } else {
          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.`);
        }
        const { done: dlDone, skipped: dlSkipped } = await downloadAlbumTracks({ jobId, artist, albumTitle: album || title, tracks, artworkUrl });
        const allSkipped  = dlSkipped === tracks.length;
        const someSkipped = dlSkipped > 0 && !allSkipped;
        const msg = allSkipped
          ? `Album bereits vorhanden – alle ${dlSkipped} Tracks übersprungen`
          : someSkipped
            ? `Album fertig! (${dlDone} geladen, ${dlSkipped} bereits vorhanden)`
            : `Album "${album || title}" fertig!`;
        updateJob(jobId, { status: 'done', progress: 100, message: msg, skipped: allSkipped });

      } 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!` });

      } else if (type === 'playlist') {
        const plTracks = req.body.tracks || [];
        if (!plTracks.length) throw new Error('Keine Tracks übergeben');
        log(jobId, `🎵 Playlist "${title}" — ${plTracks.length} Tracks`);
        let done = 0, skipped = 0;
        const CONC = CONFIG.maxParallel || 2;
        for (let i = 0; i < plTracks.length; i += CONC) {
          const batch = plTracks.slice(i, i + CONC);
          const batchResults = await Promise.allSettled(batch.map(async track => {
            const trackTitle  = track.trackName  || '';
            const trackArtist = track.artistName || artist || '';
            const searchArtist = trackArtist.split(',')[0].trim();
            log(jobId, `📋 iTunes: "${trackArtist} – ${trackTitle}"`);
            const itunes = await lookupItunesTrackMeta(searchArtist, trackTitle);
            return downloadTrack({
              jobId,
              artist:      trackArtist,
              albumArtist: trackArtist,
              title:       trackTitle,
              album:       itunes.album       || track.collectionName || '',
              year:        itunes.year        || (track.releaseDate ? new Date(track.releaseDate).getFullYear() : undefined),
              trackNum:    itunes.trackNum    || track.trackNumber    || undefined,
              totalTracks: itunes.totalTracks || undefined,
              genre:       itunes.genre       || track.primaryGenreName || undefined,
              artworkUrl:  itunes.artworkUrl  || track.artworkUrl100  || artworkUrl || '',
              explicit:    track.trackExplicitness === 'explicit',
              durationMs:  itunes.durationMs  || track.durationMs    || undefined,
            });
          }));
          for (let j = 0; j < batchResults.length; j++) {
            const r = batchResults[j];
            if (r.status === 'rejected') {
              log(jobId, `⚠️  Fehler bei "${batch[j].trackName || '?'}": ${r.reason?.message || r.reason}`);
            } else if (r.value?.skipped) {
              skipped++;
            } else {
              done++;
            }
            updateJob(jobId, { progress: Math.round(((done + skipped) / plTracks.length) * 90) });
          }
        }
        const allSkipped = skipped === plTracks.length;
        updateJob(jobId, {
          status: 'done', progress: 100, skipped: allSkipped,
          message: allSkipped
            ? `Alle ${skipped} Tracks bereits vorhanden`
            : `Fertig! ${done} geladen${skipped ? `, ${skipped} übersprungen` : ''}`,
        });
      }
    } catch (err) {
      console.error(`[${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));
});

// ─── ABS PROXY ───────────────────────────────────────────────────────────────
// Forwards API calls to Audiobookshelf to avoid CORS restrictions in the browser.
// The browser sends X-ABS-URL and X-ABS-Token headers; audio streaming uses
// direct <audio src> URLs and is unaffected by CORS.
app.all('/api/abs-proxy/*path', async (req, res) => {
  const absBase  = req.headers['x-abs-url'];
  const absToken = req.headers['x-abs-token'];
  if (!absBase || !absToken) { res.status(400).json({ error: 'Missing X-ABS-URL or X-ABS-Token' }); return; }

  // Strip the proxy prefix to get the ABS path (e.g. /api/me, /api/libraries/…)
  const absPath = req.path.replace(/^\/api\/abs-proxy/, '');
  const qs      = Object.keys(req.query).length ? '?' + new URLSearchParams(req.query).toString() : '';
  const url     = `${absBase}${absPath}${qs}`;

  const fwdHeaders = { 'Authorization': `Bearer ${absToken}`, 'Content-Type': 'application/json' };
  const opts = { method: req.method, headers: fwdHeaders };
  if (req.method !== 'GET' && req.method !== 'HEAD' && req.body && Object.keys(req.body).length) {
    opts.body = JSON.stringify(req.body);
  }

  try {
    const upstream = await fetch(url, opts);
    const text = await upstream.text();
    res.status(upstream.status)
       .setHeader('Content-Type', upstream.headers.get('Content-Type') || 'application/json')
       .send(text);
  } catch (e) {
    res.status(502).json({ error: `ABS proxy error: ${e.message}` });
  }
});

// ─── 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(`   Download backend : ${CONFIG.downloadBackend}`);
  if (CONFIG.downloadBackend !== 'ytdlp') {
    console.log(`   Squid quality    : ${CONFIG.squidQuality}`);
  }
  console.log(`   yt-dlp           : ${ytdlpVersion}`);
  console.log('');
});