Exit daily challenge screen when going offline

This sort of thing is bound to happen when rewriting screens from
scratch without invoking abstract eldritch entities sometimes. Damned if
you do, damned if you don't...

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

@@ -21,6 +21,7 @@ using osu.Game.Database;
 using osu.Game.Graphics.Containers;
 using osu.Game.Graphics.UserInterface;
 using osu.Game.Localisation;
+using osu.Game.Online.API;
 using osu.Game.Online.API.Requests.Responses;
 using osu.Game.Online.Metadata;
 using osu.Game.Online.Multiplayer;
@@ -48,6 +49,8 @@ namespace osu.Game.Screens.OnlinePlay.DailyChallenge
         /// </summary>
         private readonly Bindable<IReadOnlyList<Mod>> userMods = new Bindable<IReadOnlyList<Mod>>(Array.Empty<Mod>());
 
+        private readonly IBindable<APIState> apiState = new Bindable<APIState>();
+
         private OnlinePlayScreenWaveContainer waves = null!;
         private DailyChallengeLeaderboard leaderboard = null!;
         private RoomModSelectOverlay userModsSelectOverlay = null!;
@@ -84,6 +87,9 @@ namespace osu.Game.Screens.OnlinePlay.DailyChallenge
         [Resolved]
         private UserLookupCache userLookupCache { get; set; } = null!;
 
+        [Resolved]
+        protected IAPIProvider API { get; private set; } = null!;
+
         public override bool DisallowExternalBeatmapRulesetChanges => true;
 
         public DailyChallenge(Room room)
@@ -358,6 +364,9 @@ namespace osu.Game.Screens.OnlinePlay.DailyChallenge
             userModsSelectOverlayRegistration = overlayManager?.RegisterBlockingOverlay(userModsSelectOverlay);
             userModsSelectOverlay.SelectedItem.Value = playlistItem;
             userMods.BindValueChanged(_ => Scheduler.AddOnce(updateMods), true);
+
+            apiState.BindTo(API.State);
+            apiState.BindValueChanged(onlineStateChanged, true);
         }
 
         private void trySetDailyChallengeBeatmap()
@@ -368,6 +377,25 @@ namespace osu.Game.Screens.OnlinePlay.DailyChallenge
             applyLoopingToTrack();
         }
 
+        private void onlineStateChanged(ValueChangedEvent<APIState> state) => Schedule(() =>
+        {
+            if (state.NewValue != APIState.Online)
+                Schedule(forcefullyExit);
+        });
+
+        private void forcefullyExit()
+        {
+            Logger.Log($"{this} forcefully exiting due to loss of API connection");
+
+            // This is temporary since we don't currently have a way to force screens to be exited
+            // See also: `OnlinePlayScreen.forcefullyExit()`
+            if (this.IsCurrentScreen())
+            {
+                while (this.IsCurrentScreen())
+                    this.Exit();
+            }
+        }
+
         public override void OnEntering(ScreenTransitionEvent e)
         {
             base.OnEntering(e);

osu.Game/Screens/OnlinePlay/OnlinePlayScreen.cs

@@ -99,6 +99,7 @@ namespace osu.Game.Screens.OnlinePlay
             Logger.Log($"{this} forcefully exiting due to loss of API connection");
 
             // This is temporary since we don't currently have a way to force screens to be exited
+            // See also: `DailyChallenge.forcefullyExit()`
             if (this.IsCurrentScreen())
             {
                 while (this.IsCurrentScreen())