Updated certain events to have more concrete event arguments. Added try-catch block around playlist save logic. Added DispatchQueue where necessary.

Harmonia.Core/Player/AudioPlayer.cs

@@ -20,9 +20,13 @@ public class AudioPlayer : IAudioPlayer
         }
         protected set
         {
+            Playlist? oldPlaylist = _playlist;
             _playlist = value;
+
             NotifyPropertyChanged(nameof(Playlist));
-            PlaylistChanged?.Invoke(this, new());
+
+            PlaylistChangedEventArgs eventArgs = new(oldPlaylist, value);
+            PlaylistChanged?.Invoke(this, eventArgs);
         }
     }
 
@@ -37,9 +41,13 @@ public class AudioPlayer : IAudioPlayer
         }
         protected set
         {
+            PlaylistSong? oldSong = _playingSong;
             _playingSong = value;
+
             NotifyPropertyChanged(nameof(PlayingSong));
-            PlayingSongChanged?.Invoke(this, new());
+
+            PlayingSongChangedEventArgs eventArgs = new(oldSong, value);
+            PlayingSongChanged?.Invoke(this, eventArgs);
         }
     }
 
@@ -115,8 +123,8 @@ public class AudioPlayer : IAudioPlayer
 
     protected virtual int PreviousSongSecondsThreshold => 5;
 
-    public event EventHandler? PlaylistChanged;
-    public event EventHandler? PlayingSongChanged;
+    public event EventHandler<PlaylistChangedEventArgs>? PlaylistChanged;
+    public event EventHandler<PlayingSongChangedEventArgs>? PlayingSongChanged;
     public event PropertyChangedEventHandler? PropertyChanged;
 
     public AudioPlayer(IAudioEngine audioEngine, IPlaylistManager playlistManager)

Harmonia.Core/Player/IAudioPlayer.cs

@@ -24,7 +24,7 @@ public interface IAudioPlayer
     Task PreviousAsync();
     Task NextAsync();
 
-    event EventHandler PlaylistChanged;
-    event EventHandler PlayingSongChanged;
+    event EventHandler<PlaylistChangedEventArgs> PlaylistChanged;
+    event EventHandler<PlayingSongChangedEventArgs> PlayingSongChanged;
     event PropertyChangedEventHandler PropertyChanged;
 }

Harmonia.Core/Player/PlayingSongChangedEventArgs.cs

@@ -0,0 +1,9 @@
+using Harmonia.Core.Playlists;
+
+namespace Harmonia.Core.Player;
+
+public class PlayingSongChangedEventArgs(PlaylistSong? oldSong, PlaylistSong? newSong) : EventArgs
+{
+    public PlaylistSong? OldSong { get; } = oldSong;
+    public PlaylistSong? NewSong { get; } = newSong;
+}

Harmonia.Core/Player/PlaylistChangedEventArgs.cs

@@ -0,0 +1,9 @@
+using Harmonia.Core.Playlists;
+
+namespace Harmonia.Core.Player;
+
+public class PlaylistChangedEventArgs(Playlist? oldPlaylist, Playlist? newPlaylist) : EventArgs
+{
+    public Playlist? OldPlaylist { get; } = oldPlaylist;
+    public Playlist? NewPlaylist { get; } = newPlaylist;
+}

Harmonia.Core/Playlists/IPlaylistManager.cs

@@ -13,4 +13,5 @@ public interface IPlaylistManager
     event EventHandler? CurrentPlaylistChanged;
     event EventHandler<PlaylistAddedEventArgs> PlaylistAdded;
     event EventHandler<PlaylistRemovedEventArgs> PlaylistRemoved;
+    event EventHandler<PlaylistSaveFailedEventArgs>? PlaylistSaveFailed;
 }

Harmonia.Core/Playlists/PlaylistManager.cs

@@ -25,6 +25,7 @@ public class PlaylistManager : IPlaylistManager
     public event EventHandler? CurrentPlaylistChanged;
     public event EventHandler<PlaylistAddedEventArgs>? PlaylistAdded;
     public event EventHandler<PlaylistRemovedEventArgs>? PlaylistRemoved;
+    public event EventHandler<PlaylistSaveFailedEventArgs>? PlaylistSaveFailed;
 
     public PlaylistManager(IPlaylistRepository playlistRepository)
     {
@@ -60,7 +61,7 @@ public class PlaylistManager : IPlaylistManager
             _playlistsBySongUid[song.UID] = playlist;
         }
 
-        await playlistRepository.SaveAsync(playlist);
+        await SavePlaylistAsync(playlist);
 
         PlaylistAdded?.Invoke(this, new(playlist));
 
@@ -108,6 +109,18 @@ public class PlaylistManager : IPlaylistManager
                 break;
         }
 
-        await playlistRepository.SaveAsync(playlist);
+        await SavePlaylistAsync(playlist);
+    }
+
+    private async Task SavePlaylistAsync(Playlist playlist)
+    {
+        try
+        {
+            await playlistRepository.SaveAsync(playlist);
+        }
+        catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
+        {
+            PlaylistSaveFailed?.Invoke(this, new(playlist, ex));
+        }
     }
 }

Harmonia.Core/Playlists/PlaylistSaveFailedEventArgs.cs

@@ -0,0 +1,7 @@
+namespace Harmonia.Core.Playlists;
+
+public class PlaylistSaveFailedEventArgs(Playlist playlist, Exception exception) : EventArgs
+{
+    public Playlist Playlist { get; } = playlist;
+    public Exception Exception { get; } = exception;
+}