From 11a7057289b20a195bd1be91e1a11681d2f29eb2 Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Tue, 8 Dec 2020 17:41:56 +0900
Subject: [PATCH] Add notification flow for user state changes in room

---
 .../RealtimeMultiplayer/IMultiplayerServer.cs     |  7 +++++++
 .../RealtimeMultiplayer/ISpectatorClient.cs       |  7 +++++++
 .../RealtimeMultiplayer/InvalidStateChange.cs     | 15 +++++++++++++++
 3 files changed, 29 insertions(+)
 create mode 100644 osu.Game/Online/RealtimeMultiplayer/InvalidStateChange.cs

diff --git a/osu.Game/Online/RealtimeMultiplayer/IMultiplayerServer.cs b/osu.Game/Online/RealtimeMultiplayer/IMultiplayerServer.cs
index 44d7ecc2e9..ad4aa5d2c2 100644
--- a/osu.Game/Online/RealtimeMultiplayer/IMultiplayerServer.cs
+++ b/osu.Game/Online/RealtimeMultiplayer/IMultiplayerServer.cs
@@ -30,5 +30,12 @@ namespace osu.Game.Online.RealtimeMultiplayer
         /// </summary>
         /// <param name="settings">The new settings to apply.</param>
         Task ChangeSettings(MultiplayerRoomSettings settings);
+
+        /// <summary>
+        /// Change the local user state in the currently joined room.
+        /// </summary>
+        /// <param name="newState">The proposed new state.</param>
+        /// <exception cref="InvalidStateChange">If the state change requested is not valid, given the previous state or room state.</exception>
+        Task ChangeState(MultiplayerUserState newState);
     }
 }
diff --git a/osu.Game/Online/RealtimeMultiplayer/ISpectatorClient.cs b/osu.Game/Online/RealtimeMultiplayer/ISpectatorClient.cs
index f3dff0de86..fa06652474 100644
--- a/osu.Game/Online/RealtimeMultiplayer/ISpectatorClient.cs
+++ b/osu.Game/Online/RealtimeMultiplayer/ISpectatorClient.cs
@@ -39,5 +39,12 @@ namespace osu.Game.Online.RealtimeMultiplayer
         /// </summary>
         /// <param name="newSettings">The updated room settings.</param>
         Task SettingsChanged(MultiplayerRoomSettings newSettings);
+
+        /// <summary>
+        /// Signals that a user in this room changed their state.
+        /// </summary>
+        /// <param name="userId">The ID of the user performing a state change.</param>
+        /// <param name="state">The new state of the user.</param>
+        Task UserStateChanged(long userId, MultiplayerUserState state);
     }
 }
diff --git a/osu.Game/Online/RealtimeMultiplayer/InvalidStateChange.cs b/osu.Game/Online/RealtimeMultiplayer/InvalidStateChange.cs
new file mode 100644
index 0000000000..d1016e95cb
--- /dev/null
+++ b/osu.Game/Online/RealtimeMultiplayer/InvalidStateChange.cs
@@ -0,0 +1,15 @@
+// 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;
+
+namespace osu.Game.Online.RealtimeMultiplayer
+{
+    public class InvalidStateChange : Exception
+    {
+        public InvalidStateChange(MultiplayerUserState oldState, MultiplayerUserState newState)
+            : base($"Cannot change from {oldState} to {newState}")
+        {
+        }
+    }
+}