Add metadata endpoint to refresh friend listing (#36386)

Alternative to / closes #36341
See also: ppy/osu-server-spectator#415

This is a simple solution by adding a spectator endpoint to refresh the
friend listing. A more complicated form of this is to make
adding/removing friends only via spectator, but that would require
osu-web changes too.

Author: smoogipoo

osu.Game/Online/Metadata/IMetadataServer.cs

@@ -53,5 +53,10 @@ public interface IMetadataServer
         /// Signals to the server that the current user would like to stop receiving updates about the state of the multiplayer room with the given <paramref name="id"/>.
         /// </summary>
         Task EndWatchingMultiplayerRoom(long id);
+
+        /// <summary>
+        /// Refresh this user's friend listing.
+        /// </summary>
+        Task RefreshFriends();
     }
 }

osu.Game/Online/Metadata/MetadataClient.cs

@@ -9,6 +9,7 @@
 using osu.Framework.Bindables;
 using osu.Framework.Graphics;
 using osu.Game.Online.API;
+using osu.Game.Online.API.Requests.Responses;
 using osu.Game.Online.Multiplayer;
 using osu.Game.Users;
 
@@ -21,6 +22,16 @@ public abstract partial class MetadataClient : Component, IMetadataClient, IMeta
         [Resolved]
         private IAPIProvider api { get; set; } = null!;
 
+        private readonly IBindableList<APIRelation> localFriends = new BindableList<APIRelation>();
+
+        protected override void LoadComplete()
+        {
+            base.LoadComplete();
+
+            localFriends.BindTo(api.LocalUserState.Friends);
+            localFriends.BindCollectionChanged((_, _) => RefreshFriends().FireAndForget());
+        }
+
         #region Beatmap metadata updates
 
         public abstract Task<BeatmapUpdates> GetChangesSince(int queueId);
@@ -152,6 +163,8 @@ public void Dispose()
 
         public abstract Task EndWatchingMultiplayerRoom(long id);
 
+        public abstract Task RefreshFriends();
+
         public event Action<MultiplayerRoomScoreSetEvent>? MultiplayerRoomScoreSet;
 
         Task IMetadataClient.MultiplayerRoomScoreSet(MultiplayerRoomScoreSetEvent roomScoreSetEvent)

osu.Game/Online/Metadata/OnlineMetadataClient.cs

@@ -288,6 +288,15 @@ public override async Task EndWatchingMultiplayerRoom(long id)
             Logger.Log($@"{nameof(OnlineMetadataClient)} stopped watching multiplayer room with ID {id}", LoggingTarget.Network);
         }
 
+        public override async Task RefreshFriends()
+        {
+            if (connector?.IsConnected.Value != true)
+                throw new OperationCanceledException();
+
+            Debug.Assert(connection != null);
+            await connection.InvokeAsync(nameof(IMetadataServer.RefreshFriends)).ConfigureAwait(false);
+        }
+
         public override async Task DisconnectRequested()
         {
             await base.DisconnectRequested().ConfigureAwait(false);

osu.Game/Tests/Visual/Metadata/TestMetadataClient.cs

@@ -128,6 +128,8 @@ public override Task<MultiplayerPlaylistItemStats[]> BeginWatchingMultiplayerRoo
 
         public override Task EndWatchingMultiplayerRoom(long id) => Task.CompletedTask;
 
+        public override Task RefreshFriends() => Task.CompletedTask;
+
         public void Disconnect()
         {
             isConnected.Value = false;