Move ready-up operation logic again to client

To salvage ready up button tests.

osu.Game.Tests/Visual/Multiplayer/TestSceneMultiplayerReadyButton.cs

@@ -34,6 +34,8 @@ namespace osu.Game.Tests.Visual.Multiplayer
         [Cached]
         private OngoingOperationTracker ongoingOperationTracker = new OngoingOperationTracker();
 
+        private IDisposable toggleReadyOperation;
+
         [BackgroundDependencyLoader]
         private void load(GameHost host, AudioManager audio)
         {
@@ -61,6 +63,14 @@ namespace osu.Game.Tests.Visual.Multiplayer
                         Beatmap = { Value = beatmap },
                         Ruleset = { Value = beatmap.Ruleset }
                     }
+                },
+                OnToggleReady = async () =>
+                {
+                    toggleReadyOperation = ongoingOperationTracker.BeginOperation();
+
+                    bool gameplayStarted = await Client.ToggleReady();
+                    if (!gameplayStarted)
+                        toggleReadyOperation.Dispose();
                 }
             };
         });
@@ -168,15 +178,11 @@ namespace osu.Game.Tests.Visual.Multiplayer
 
         private void verifyGameplayStartFlow()
         {
-            IDisposable gameplayStartOperation = null;
-
-            AddStep("hook up tracker", () => button.OnReady = () => gameplayStartOperation = ongoingOperationTracker.BeginOperation());
-
             addClickButtonStep();
             AddAssert("user waiting for load", () => Client.Room?.Users[0].State == MultiplayerUserState.WaitingForLoad);
             AddAssert("ready button disabled", () => !button.ChildrenOfType<OsuButton>().Single().Enabled.Value);
 
-            AddStep("transitioned to gameplay", () => gameplayStartOperation.Dispose());
+            AddStep("transitioned to gameplay", () => toggleReadyOperation.Dispose());
             AddAssert("ready button enabled", () => button.ChildrenOfType<OsuButton>().Single().Enabled.Value);
         }
     }

osu.Game/Online/Multiplayer/StatefulMultiplayerClient.cs

@@ -183,6 +183,39 @@ namespace osu.Game.Online.Multiplayer
             });
         }
 
+        /// <summary>
+        /// Toggles the <see cref="LocalUser"/>'s ready state.
+        /// </summary>
+        /// <returns><c>true</c> if this toggle triggered a gameplay start; <c>false</c> otherwise.</returns>
+        /// <exception cref="InvalidOperationException">If a toggle of ready state is not valid at this time.</exception>
+        public async Task<bool> ToggleReady()
+        {
+            var localUser = LocalUser;
+
+            if (localUser == null)
+                return false;
+
+            switch (localUser.State)
+            {
+                case MultiplayerUserState.Idle:
+                    await ChangeState(MultiplayerUserState.Ready);
+                    return false;
+
+                case MultiplayerUserState.Ready:
+                    if (Room?.Host?.Equals(localUser) == true)
+                    {
+                        await StartMatch();
+                        return true;
+                    }
+
+                    await ChangeState(MultiplayerUserState.Idle);
+                    return false;
+
+                default:
+                    throw new InvalidOperationException($"Cannot toggle ready when in {localUser.State}");
+            }
+        }
+
         public abstract Task TransferHost(int userId);
 
         public abstract Task ChangeSettings(MultiplayerRoomSettings settings);

osu.Game/Screens/OnlinePlay/Multiplayer/Match/MultiplayerMatchFooter.cs

@@ -20,9 +20,9 @@ namespace osu.Game.Screens.OnlinePlay.Multiplayer.Match
 
         public readonly Bindable<PlaylistItem> SelectedItem = new Bindable<PlaylistItem>();
 
-        public Action OnReady
+        public Action OnToggleReady
         {
-            set => readyButton.OnReady = value;
+            set => readyButton.OnToggleReady = value;
         }
 
         private readonly Drawable background;

osu.Game/Screens/OnlinePlay/Multiplayer/Match/MultiplayerReadyButton.cs

@@ -23,7 +23,7 @@ namespace osu.Game.Screens.OnlinePlay.Multiplayer.Match
     {
         public Bindable<PlaylistItem> SelectedItem => button.SelectedItem;
 
-        public Action OnReady
+        public Action OnToggleReady
         {
             set => button.Action = value;
         }

osu.Game/Screens/OnlinePlay/Multiplayer/MultiplayerMatchSubScreen.cs

@@ -162,7 +162,7 @@ namespace osu.Game.Screens.OnlinePlay.Multiplayer
                             new MultiplayerMatchFooter
                             {
                                 SelectedItem = { BindTarget = SelectedItem },
-                                OnReady = onReady
+                                OnToggleReady = onToggleReady
                             }
                         }
                     },
@@ -209,27 +209,22 @@ namespace osu.Game.Screens.OnlinePlay.Multiplayer
 
         private void onPlaylistChanged(object sender, NotifyCollectionChangedEventArgs e) => SelectedItem.Value = Playlist.FirstOrDefault();
 
-        private void onReady()
+        private void onToggleReady()
-        {
-            var localUser = client.LocalUser;
-
-            if (localUser == null)
-                return;
-
-            if (localUser.State == MultiplayerUserState.Idle)
-                client.ChangeState(MultiplayerUserState.Ready).CatchUnobservedExceptions(true);
-            else
-            {
-                if (client.Room?.Host?.Equals(localUser) == true)
         {
             Debug.Assert(gameplayStartOperation == null);
             gameplayStartOperation = ongoingOperationTracker.BeginOperation();
 
-                    client.StartMatch().CatchUnobservedExceptions(true);
+            client.ToggleReady()
-                }
+                  .ContinueWith(t =>
-                else
+                  {
-                    client.ChangeState(MultiplayerUserState.Idle).CatchUnobservedExceptions(true);
+                      // if gameplay was started, the button will be unblocked on load requested.
-            }
+                      if (t.Result) return;
+
+                      // gameplay was not started; unblock button.
+                      gameplayStartOperation?.Dispose();
+                      gameplayStartOperation = null;
+                  })
+                  .CatchUnobservedExceptions();
         }
 
         private void onLoadRequested()