feat: added initial version ReplayGain functionality, still in development

app/src/main/java/com/cappielloantonio/tempo/model/ReplayGain.kt

@@ -0,0 +1,9 @@
+package com.cappielloantonio.tempo.model
+
+import androidx.annotation.Keep
+
+@Keep
+data class ReplayGain(
+    var trackGain: Float = 0f,
+    var albumGain: Float = 0f,
+)

app/src/main/java/com/cappielloantonio/tempo/util/ReplayGainUtil.java

@@ -0,0 +1,107 @@
+package com.cappielloantonio.tempo.util;
+
+import androidx.media3.common.Metadata;
+import androidx.media3.common.Tracks;
+import androidx.media3.exoplayer.ExoPlayer;
+
+import com.cappielloantonio.tempo.model.ReplayGain;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+
+public class ReplayGainUtil {
+    private static final String[] tags = {"REPLAYGAIN_TRACK_GAIN", "REPLAYGAIN_ALBUM_GAIN", "R128_TRACK_GAIN", "R128_ALBUM_GAIN"};
+
+    public static void setReplayGain(ExoPlayer player, Tracks tracks) {
+        List<Metadata> metadata = getMetadata(tracks);
+        List<ReplayGain> gains = getReplayGains(metadata);
+
+        applyReplayGain(player, gains);
+    }
+
+    private static List<Metadata> getMetadata(Tracks tracks) {
+        List<Metadata> metadata = new ArrayList<>();
+
+        for (int i = 0; i < tracks.getGroups().size(); i++) {
+            Tracks.Group group = tracks.getGroups().get(i);
+
+            for (int j = 0; j < group.getMediaTrackGroup().length; j++) {
+                metadata.add(group.getTrackFormat(j).metadata);
+            }
+        }
+
+        return metadata;
+    }
+
+    private static List<ReplayGain> getReplayGains(List<Metadata> metadata) {
+        List<ReplayGain> gains = new ArrayList<>();
+
+        for (int i = 0; i < metadata.size(); i++) {
+            for (int j = 0; j < metadata.get(i).length(); j++) {
+                Metadata.Entry entry = metadata.get(i).get(j);
+
+                if (checkReplayGain(entry)) {
+                    ReplayGain replayGain = setReplayGains(entry);
+                    gains.add(replayGain);
+                }
+            }
+        }
+
+        return gains;
+    }
+
+    private static boolean checkReplayGain(Metadata.Entry entry) {
+        for (String tag : tags) {
+            if (entry.toString().contains(tag)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    private static ReplayGain setReplayGains(Metadata.Entry entry) {
+        ReplayGain replayGain = new ReplayGain();
+
+        if (entry.toString().contains(tags[0])) {
+            replayGain.setTrackGain(parseReplayGainTag(entry));
+        }
+
+        if (entry.toString().contains(tags[1])) {
+            replayGain.setAlbumGain(parseReplayGainTag(entry));
+        }
+
+        if (entry.toString().contains(tags[2])) {
+            replayGain.setTrackGain(parseReplayGainTag(entry) / 256f);
+        }
+
+        if (entry.toString().contains(tags[3])) {
+            replayGain.setAlbumGain(parseReplayGainTag(entry) / 256f);
+        }
+
+        return replayGain;
+    }
+
+    private static Float parseReplayGainTag(Metadata.Entry entry) {
+        try {
+            return Float.parseFloat(entry.toString().replaceAll("[^\\d.]", ""));
+        } catch (NumberFormatException exception) {
+            return 0f;
+        }
+    }
+
+    private static void applyReplayGain(ExoPlayer player, List<ReplayGain> gains) {
+        if (Objects.equals(Preferences.getReplayGainMode(), "disabled") || gains.size() == 0) {
+            setReplayGain(player, 0f);
+        } else if (Objects.equals(Preferences.getReplayGainMode(), "track")) {
+            setReplayGain(player, gains.get(0).getTrackGain() != 0f ? gains.get(0).getTrackGain() : gains.get(0).getAlbumGain());
+        } else if (Objects.equals(Preferences.getReplayGainMode(), "album")) {
+            setReplayGain(player, gains.get(0).getAlbumGain() != 0f ? gains.get(0).getAlbumGain() : gains.get(0).getTrackGain());
+        }
+    }
+
+    private static void setReplayGain(ExoPlayer player, float gain) {
+        player.setVolume((float) Math.pow(10f, -gain / 20f));
+    }
+}

app/src/notquitemy/java/com/cappielloantonio/tempo/service/MediaService.kt

@@ -10,12 +10,15 @@ import androidx.media3.common.*
 import androidx.media3.common.util.UnstableApi
 import androidx.media3.exoplayer.ExoPlayer
 import androidx.media3.exoplayer.source.DefaultMediaSourceFactory
+import androidx.media3.exoplayer.source.TrackGroupArray
+import androidx.media3.exoplayer.trackselection.TrackSelectionArray
 import androidx.media3.session.*
 import androidx.media3.session.MediaSession.ControllerInfo
 import com.cappielloantonio.tempo.R
 import com.cappielloantonio.tempo.ui.activity.MainActivity
 import com.cappielloantonio.tempo.util.Constants
 import com.cappielloantonio.tempo.util.DownloadUtil
+import com.cappielloantonio.tempo.util.ReplayGainUtil
 import com.google.common.collect.ImmutableList
 import com.google.common.util.concurrent.Futures
 import com.google.common.util.concurrent.ListenableFuture
@@ -170,6 +173,10 @@ class MediaService : MediaLibraryService() {
                 }
             }
 
+            override fun onTracksChanged(tracks: Tracks) {
+                ReplayGainUtil.setReplayGain(player, tracks)
+            }
+
             override fun onIsPlayingChanged(isPlaying: Boolean) {
                 if (!isPlaying) {
                     MediaManager.setPlayingPausedTimestamp(