Add client/server models for allowing clients to receive realtime playlist updates

osu.Game/Online/Metadata/IMetadataClient.cs

@@ -26,5 +26,11 @@ namespace osu.Game.Online.Metadata
         /// Null value means there is no "daily challenge" currently active.
         /// </summary>
         Task DailyChallengeUpdated(DailyChallengeInfo? info);
+
+        /// <summary>
+        /// Delivers information that a multiplayer score was set in a watched room.
+        /// To receive these, the client must call <see cref="IMetadataServer.BeginWatchingMultiplayerRoom"/> for a given room first.
+        /// </summary>
+        Task MultiplayerRoomScoreSet(MultiplayerRoomScoreSetEvent roomScoreSetEvent);
     }
 }

osu.Game/Online/Metadata/IMetadataServer.cs

@@ -43,5 +43,15 @@ namespace osu.Game.Online.Metadata
         /// Signals to the server that the current user would like to stop receiving updates on other users' online presence.
         /// </summary>
         Task EndWatchingUserPresence();
+
+        /// <summary>
+        /// Signals to the server that the current user would like to begin receiving updates about the state of the multiplayer room with the given <paramref name="id"/>.
+        /// </summary>
+        Task<MultiplayerPlaylistItemStats[]> BeginWatchingMultiplayerRoom(long id);
+
+        /// <summary>
+        /// 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);
     }
 }

osu.Game/Online/Metadata/MetadataClient.cs

@@ -68,6 +68,24 @@ namespace osu.Game.Online.Metadata
 
         #endregion
 
+        #region Multiplayer room watching
+
+        public abstract Task<MultiplayerPlaylistItemStats[]> BeginWatchingMultiplayerRoom(long id);
+
+        public abstract Task EndWatchingMultiplayerRoom(long id);
+
+        public event Action<MultiplayerRoomScoreSetEvent>? MultiplayerRoomScoreSet;
+
+        Task IMetadataClient.MultiplayerRoomScoreSet(MultiplayerRoomScoreSetEvent roomScoreSetEvent)
+        {
+            if (MultiplayerRoomScoreSet != null)
+                Schedule(MultiplayerRoomScoreSet, roomScoreSetEvent);
+
+            return Task.CompletedTask;
+        }
+
+        #endregion
+
         #region Disconnection handling
 
         public event Action? Disconnecting;

osu.Game/Online/Metadata/MultiplayerPlaylistItemStats.cs

@@ -0,0 +1,29 @@
+// 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 MessagePack;
+
+namespace osu.Game.Online.Metadata
+{
+    [MessagePackObject]
+    [Serializable]
+    public class MultiplayerPlaylistItemStats
+    {
+        public const int TOTAL_SCORE_DISTRIBUTION_BINS = 13;
+
+        /// <summary>
+        /// The ID of the playlist item which these stats pertain to.
+        /// </summary>
+        [Key(0)]
+        public long PlaylistItemID { get; set; }
+
+        /// <summary>
+        /// The count of scores with given total ranges in the room.
+        /// The ranges are bracketed into <see cref="TOTAL_SCORE_DISTRIBUTION_BINS"/> bins, each of 100,000 score width.
+        /// The last bin will contain count of all scores with total of 1,200,000 or larger.
+        /// </summary>
+        [Key(1)]
+        public long[] TotalScoreDistribution { get; set; } = new long[TOTAL_SCORE_DISTRIBUTION_BINS];
+    }
+}

osu.Game/Online/Metadata/MultiplayerRoomScoreSetEvent.cs

@@ -0,0 +1,50 @@
+// 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 MessagePack;
+
+namespace osu.Game.Online.Metadata
+{
+    [Serializable]
+    [MessagePackObject]
+    public class MultiplayerRoomScoreSetEvent
+    {
+        /// <summary>
+        /// The ID of the room in which the score was set.
+        /// </summary>
+        [Key(0)]
+        public long RoomID { get; set; }
+
+        /// <summary>
+        /// The ID of the playlist item on which the score was set.
+        /// </summary>
+        [Key(1)]
+        public long PlaylistItemID { get; set; }
+
+        /// <summary>
+        /// The ID of the score set.
+        /// </summary>
+        [Key(2)]
+        public long ScoreID { get; set; }
+
+        /// <summary>
+        /// The ID of the user who set the score.
+        /// </summary>
+        [Key(3)]
+        public int UserID { get; set; }
+
+        /// <summary>
+        /// The total score set by the player.
+        /// </summary>
+        [Key(4)]
+        public long TotalScore { get; set; }
+
+        /// <summary>
+        /// If the set score is the user's new best on a playlist item, this member will contain the user's new rank in the room overall.
+        /// Otherwise, it will contain <see langword="null"/>.
+        /// </summary>
+        [Key(5)]
+        public int? NewRank { get; set; }
+    }
+}

osu.Game/Online/Metadata/OnlineMetadataClient.cs

@@ -62,6 +62,7 @@ namespace osu.Game.Online.Metadata
                     connection.On<BeatmapUpdates>(nameof(IMetadataClient.BeatmapSetsUpdated), ((IMetadataClient)this).BeatmapSetsUpdated);
                     connection.On<int, UserPresence?>(nameof(IMetadataClient.UserPresenceUpdated), ((IMetadataClient)this).UserPresenceUpdated);
                     connection.On<DailyChallengeInfo?>(nameof(IMetadataClient.DailyChallengeUpdated), ((IMetadataClient)this).DailyChallengeUpdated);
+                    connection.On<MultiplayerRoomScoreSetEvent>(nameof(IMetadataClient.MultiplayerRoomScoreSet), ((IMetadataClient)this).MultiplayerRoomScoreSet);
                     connection.On(nameof(IStatefulUserHubClient.DisconnectRequested), ((IMetadataClient)this).DisconnectRequested);
                 };
 
@@ -240,6 +241,24 @@ namespace osu.Game.Online.Metadata
             return Task.CompletedTask;
         }
 
+        public override async Task<MultiplayerPlaylistItemStats[]> BeginWatchingMultiplayerRoom(long id)
+        {
+            if (connector?.IsConnected.Value != true)
+                throw new OperationCanceledException();
+
+            Debug.Assert(connection != null);
+            return await connection.InvokeAsync<MultiplayerPlaylistItemStats[]>(nameof(IMetadataServer.BeginWatchingMultiplayerRoom), id).ConfigureAwait(false);
+        }
+
+        public override async Task EndWatchingMultiplayerRoom(long id)
+        {
+            if (connector?.IsConnected.Value != true)
+                throw new OperationCanceledException();
+
+            Debug.Assert(connection != null);
+            await connection.InvokeAsync(nameof(IMetadataServer.EndWatchingMultiplayerRoom)).ConfigureAwait(false);
+        }
+
         public override async Task DisconnectRequested()
         {
             await base.DisconnectRequested().ConfigureAwait(false);

osu.Game/Screens/OnlinePlay/DailyChallenge/DailyChallengeScoreBreakdown.cs

@@ -11,6 +11,7 @@ using osu.Framework.Localisation;
 using osu.Game.Graphics;
 using osu.Game.Graphics.Sprites;
 using osu.Game.Graphics.UserInterface;
+using osu.Game.Online.Metadata;
 using osu.Game.Overlays;
 using osu.Game.Scoring;
 using osuTK;
@@ -21,7 +22,7 @@ namespace osu.Game.Screens.OnlinePlay.DailyChallenge
     {
         private FillFlowContainer<Bar> barsContainer = null!;
 
-        private const int bin_count = 13;
+        private const int bin_count = MultiplayerPlaylistItemStats.TOTAL_SCORE_DISTRIBUTION_BINS;
         private long[] bins = new long[bin_count];
 
         [BackgroundDependencyLoader]

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

@@ -86,5 +86,10 @@ namespace osu.Game.Tests.Visual.Metadata
             dailyChallengeInfo.Value = info;
             return Task.CompletedTask;
         }
+
+        public override Task<MultiplayerPlaylistItemStats[]> BeginWatchingMultiplayerRoom(long id)
+            => Task.FromResult(new MultiplayerPlaylistItemStats[MultiplayerPlaylistItemStats.TOTAL_SCORE_DISTRIBUTION_BINS]);
+
+        public override Task EndWatchingMultiplayerRoom(long id) => Task.CompletedTask;
     }
 }