From 39206f41286fccb2cd641c145990732f3750fabd Mon Sep 17 00:00:00 2001
From: Eric D'Addario <ericdaddario02@gmail.com>
Date: Sat, 28 Feb 2026 15:39:50 -0500
Subject: [PATCH] feat(downloads): save replay gain tags to FLAC metadata

---
 js/api.js       | 13 ++++++++++++-
 js/downloads.js |  9 +++++++++
 js/metadata.js  |  7 +++++++
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/js/api.js b/js/api.js
index 8fe0a35..e44f867 100644
--- a/js/api.js
+++ b/js/api.js
@@ -1254,7 +1254,18 @@ export class LosslessAPI {
                         message: 'Adding metadata...',
                     });
                 }
-                blob = await addMetadataToAudio(blob, track, this, quality);
+
+                const enrichedTrack = { ...track };
+                if (lookup.info) {
+                    enrichedTrack.replayGain = {
+                        trackReplayGain: lookup.info.trackReplayGain,
+                        trackPeakAmplitude: lookup.info.trackPeakAmplitude,
+                        albumReplayGain: lookup.info.albumReplayGain,
+                        albumPeakAmplitude: lookup.info.albumPeakAmplitude,
+                    };
+                }
+
+                blob = await addMetadataToAudio(blob, enrichedTrack, this, quality);
             }
 
             // Detect actual format and fix filename extension if needed
diff --git a/js/downloads.js b/js/downloads.js
index 74d6d23..f3c16ce 100644
--- a/js/downloads.js
+++ b/js/downloads.js
@@ -323,6 +323,15 @@ async function downloadTrackBlob(track, quality, api, lyricsManager = null, sign
         }
     }
 
+    if (lookup.info) {
+        enrichedTrack.replayGain = {
+            trackReplayGain: lookup.info.trackReplayGain,
+            trackPeakAmplitude: lookup.info.trackPeakAmplitude,
+            albumReplayGain: lookup.info.albumReplayGain,
+            albumPeakAmplitude: lookup.info.albumPeakAmplitude,
+        };
+    }
+
     // Handle DASH streams (blob URLs)
     let blob;
     if (streamUrl.startsWith('blob:')) {
diff --git a/js/metadata.js b/js/metadata.js
index 6d54dd6..82ad190 100644
--- a/js/metadata.js
+++ b/js/metadata.js
@@ -587,6 +587,13 @@ function createVorbisCommentBlock(track) {
     if (track.album?.numberOfTracks) {
         comments.push(['TRACKTOTAL', String(track.album.numberOfTracks)]);
     }
+    if (track.replayGain) {
+        const { albumReplayGain, albumPeakAmplitude, trackReplayGain, trackPeakAmplitude } = track.replayGain;
+        if (albumReplayGain) comments.push(['REPLAYGAIN_ALBUM_GAIN', String(albumReplayGain)]);
+        if (albumPeakAmplitude) comments.push(['REPLAYGAIN_ALBUM_PEAK', String(albumPeakAmplitude)]);
+        if (trackReplayGain) comments.push(['REPLAYGAIN_TRACK_GAIN', String(trackReplayGain)]);
+        if (trackPeakAmplitude) comments.push(['REPLAYGAIN_TRACK_PEAK', String(trackPeakAmplitude)]);
+    }
 
     const releaseDateStr =
         track.album?.releaseDate || (track.streamStartDate ? track.streamStartDate.split('T')[0] : '');