From 252d2d3071c91704e0f0b47a739a03e493a44f32 Mon Sep 17 00:00:00 2001
From: Honey <me_honeyy@proton.me>
Date: Sat, 2 May 2026 18:03:29 +0200
Subject: [PATCH] feat: download playlist tracks in parallel batches
 (MAX_PARALLEL)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 backend/novasonic-server.js | 40 +++++++++++++++++++++----------------
 1 file changed, 23 insertions(+), 17 deletions(-)

diff --git a/backend/novasonic-server.js b/backend/novasonic-server.js
index fefb4ee..e697dbf 100644
--- a/backend/novasonic-server.js
+++ b/backend/novasonic-server.js
@@ -831,35 +831,41 @@ app.post('/api/download', async (req, res) => {
         if (!plTracks.length) throw new Error('Keine Tracks übergeben');
         log(jobId, `🎵 Playlist "${title}" — ${plTracks.length} Tracks`);
         let done = 0, skipped = 0;
-        for (const track of plTracks) {
-          try {
-            const trackTitle  = track.trackName  || '';
+        const CONC = CONFIG.maxParallel || 2;
+        for (let i = 0; i < plTracks.length; i += CONC) {
+          const batch = plTracks.slice(i, i + CONC);
+          const batchResults = await Promise.allSettled(batch.map(async track => {
+            const trackTitle   = track.trackName  || '';
             // subtitle gives "Artist1, Artist2" — use first for iTunes search, keep full for tags
-            const trackArtist = track.artistName || artist || '';
+            const trackArtist  = track.artistName || artist || '';
             const searchArtist = trackArtist.split(',')[0].trim();
-
-            // Always look up iTunes for correct album, artwork, year (Spotify flat format has none)
             log(jobId, `📋 iTunes: "${trackArtist} – ${trackTitle}"`);
             const itunes = await lookupItunesTrackMeta(searchArtist, trackTitle);
-
-            const result = await downloadTrack({
+            return downloadTrack({
               jobId,
               artist:      trackArtist,
               albumArtist: trackArtist,
               title:       trackTitle,
-              album:       itunes.album      || track.collectionName || '',
-              year:        itunes.year       || (track.releaseDate ? new Date(track.releaseDate).getFullYear() : undefined),
-              trackNum:    itunes.trackNum   || track.trackNumber   || undefined,
+              album:       itunes.album       || track.collectionName || '',
+              year:        itunes.year        || (track.releaseDate ? new Date(track.releaseDate).getFullYear() : undefined),
+              trackNum:    itunes.trackNum    || track.trackNumber    || undefined,
               totalTracks: itunes.totalTracks || undefined,
-              genre:       itunes.genre      || track.primaryGenreName || undefined,
-              artworkUrl:  itunes.artworkUrl || track.artworkUrl100 || '',
+              genre:       itunes.genre       || track.primaryGenreName || undefined,
+              artworkUrl:  itunes.artworkUrl  || track.artworkUrl100  || '',
               explicit:    track.trackExplicitness === 'explicit',
-              durationMs:  itunes.durationMs || track.durationMs   || undefined,
+              durationMs:  itunes.durationMs  || track.durationMs    || undefined,
             });
-            if (result?.skipped) skipped++; else done++;
+          }));
+          for (let j = 0; j < batchResults.length; j++) {
+            const r = batchResults[j];
+            if (r.status === 'rejected') {
+              log(jobId, `⚠️  Fehler bei "${batch[j].trackName || '?'}": ${r.reason?.message || r.reason}`);
+            } else if (r.value?.skipped) {
+              skipped++;
+            } else {
+              done++;
+            }
             updateJob(jobId, { progress: Math.round(((done + skipped) / plTracks.length) * 90) });
-          } catch(e) {
-            log(jobId, `⚠️  Fehler bei "${track.trackName || '?'}": ${e.message}`);
           }
         }
         const allSkipped = skipped === plTracks.length;