Implemented tag refresh on a playlist. Made audio file scanning truly asynchronous. Added basic playlist sorting functionality.

Harmonia.Core/Playlists/Playlist.cs

@@ -164,6 +164,8 @@ public class Playlist
 
     public void ImportTags(Song[] songs)
     {
+        List<PlaylistSong> updatedPlaylistSongs = [];
+
         foreach (Song song in songs)
         {
             PlaylistSong[] playlistSongs = [.. Songs.Where(playlistSong =>
@@ -171,10 +173,24 @@ public class Playlist
 
             foreach (PlaylistSong playlistSong in playlistSongs)
             {
-                //playlistSong.Song = song;
-                //playlistSong.Song.Update(song);
+                playlistSong.Song.Update(song);
             }
+
+            updatedPlaylistSongs.AddRange(playlistSongs);
         }
+
+        if (updatedPlaylistSongs.Count == 0)
+            return;
+
+        PlaylistUpdatedEventArgs eventArgs = new()
+        {
+            Action = PlaylistUpdateAction.Refresh,
+            Index = -1,
+            Count = updatedPlaylistSongs.Count,
+            Songs = [.. updatedPlaylistSongs]
+        };
+
+        PlaylistUpdated?.Invoke(this, eventArgs);
     }
 
     public void RemoveMissingSongs()

Harmonia.Core/Playlists/PlaylistUpdateAction.cs

@@ -17,5 +17,9 @@ public enum PlaylistUpdateAction
     /// <summary>
     /// The contents of the collection changed dramatically.
     /// </summary>
-    Reset
+    Reset,
+    /// <summary>
+    /// The tags of the songs in the collection were refreshed.
+    /// </summary>
+    Refresh
 }