Highlight active playlist. Various optimizations and fixes.

Harmonia.Core/Playlists/PlaylistRepository.cs

@@ -1,14 +1,32 @@
 using Harmonia.Core.Data;
+using System.Text.Json;
+using System.Text.Json.Serialization;
 
 namespace Harmonia.Core.Playlists;
 
 public class PlaylistRepository : JsonFileRepository<Playlist>, IPlaylistRepository
 {
+    private static readonly JsonSerializerOptions _options = new()
+    {
+        WriteIndented = true,
+        IgnoreReadOnlyProperties = true,
+        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
+    };
+
     protected override string DirectoryName => Path.Combine("Playlists");
 
-    public Playlist? GetPlaylist(PlaylistSong playlistSong)
+    protected override async Task<Playlist> DeserializeAsync(Stream stream)
     {
-        return Get().FirstOrDefault(playlist => playlist.Songs.Contains(playlistSong));
+        PlaylistDto dto = await JsonSerializer.DeserializeAsync<PlaylistDto>(stream, _options) ?? new();
+
+        return dto.ToPlaylist();
+    }
+
+    protected override Task<string> SerializeAsync(Playlist playlist)
+    {
+        PlaylistDto dto = PlaylistDto.FromPlaylist(playlist);
+
+        return Task.FromResult(JsonSerializer.Serialize(dto, _options));
     }
 
     protected override string GetNewFileName()