Fix preview tracks muting themselves

Closes #4937

osu.Game/Audio/PreviewTrackManager.cs

@@ -1,6 +1,10 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Threading.Tasks;
 using osu.Framework.Allocation;
 using osu.Framework.Audio;
 using osu.Framework.Audio.Track;
@@ -12,22 +16,24 @@
 
 namespace osu.Game.Audio
 {
-    /// <summary>
-    /// A central store for the retrieval of <see cref="PreviewTrack"/>s.
-    /// </summary>
     public class PreviewTrackManager : Component
     {
         private readonly BindableDouble muteBindable = new BindableDouble();
 
         private AudioManager audio;
-        private ITrackStore trackStore;
+        private PreviewTrackStore trackStore;
 
         private TrackManagerPreviewTrack current;
 
         [BackgroundDependencyLoader]
         private void load(AudioManager audio, FrameworkConfigManager config)
         {
-            trackStore = audio.GetTrackStore(new OnlineStore());
+            // this is a temporary solution to get around muting ourselves.
+            // todo: update this once we have a BackgroundTrackManager or similar.
+            trackStore = new PreviewTrackStore(new OnlineStore());
+
+            audio.AddItem(trackStore);
+            trackStore.AddAdjustment(AdjustableProperty.Volume, audio.VolumeTrack);
 
             this.audio = audio;
 
@@ -103,5 +109,46 @@ private void load(IPreviewTrackOwner owner)
 
             protected override Track GetTrack() => trackManager.Get($"https://b.ppy.sh/preview/{beatmapSetInfo?.OnlineBeatmapSetID}.mp3");
         }
+
+        private class PreviewTrackStore : AudioCollectionManager<AdjustableAudioComponent>, ITrackStore
+        {
+            private readonly IResourceStore<byte[]> store;
+
+            internal PreviewTrackStore(IResourceStore<byte[]> store)
+            {
+                this.store = store;
+            }
+
+            public Track GetVirtual(double length = double.PositiveInfinity)
+            {
+                if (IsDisposed) throw new ObjectDisposedException($"Cannot retrieve items for an already disposed {nameof(PreviewTrackStore)}");
+
+                var track = new TrackVirtual(length);
+                AddItem(track);
+                return track;
+            }
+
+            public Track Get(string name)
+            {
+                if (IsDisposed) throw new ObjectDisposedException($"Cannot retrieve items for an already disposed {nameof(PreviewTrackStore)}");
+
+                if (string.IsNullOrEmpty(name)) return null;
+
+                var dataStream = store.GetStream(name);
+
+                if (dataStream == null)
+                    return null;
+
+                Track track = new TrackBass(dataStream);
+                AddItem(track);
+                return track;
+            }
+
+            public Task<Track> GetAsync(string name) => Task.Run(() => Get(name));
+
+            public Stream GetStream(string name) => store.GetStream(name);
+
+            public IEnumerable<string> GetAvailableResources() => store.GetAvailableResources();
+        }
     }
 }