Disallow starting gameplay if there's not enough time in the room

osu.Game.Tests/Visual/TestCaseMatchInfo.cs

@@ -26,7 +26,7 @@ namespace osu.Game.Tests.Visual
         [BackgroundDependencyLoader]
         private void load(RulesetStore rulesets)
         {
-            Info info = new Info();
+            Info info = new Info(new Room());
             Add(info);
 
             AddStep(@"set name", () => info.Name.Value = @"Room Name?");

osu.Game/Online/Multiplayer/Room.cs

@@ -52,6 +52,10 @@ namespace osu.Game.Online.Multiplayer
             set => Duration.Value = TimeSpan.FromMinutes(value);
         }
 
+        // Only supports retrieval for now
+        [JsonProperty("ends_at")]
+        public Bindable<DateTimeOffset> EndDate = new Bindable<DateTimeOffset>();
+
         // Todo: Find a better way to do this (https://github.com/ppy/osu-framework/issues/1930)
         [JsonProperty("max_attempts", DefaultValueHandling = DefaultValueHandling.Ignore)]
         private int? maxAttempts
@@ -70,6 +74,7 @@ namespace osu.Game.Online.Multiplayer
             Type.Value = other.Type;
             MaxParticipants.Value = other.MaxParticipants;
             Participants.Value = other.Participants.Value.ToArray();
+            EndDate = other.EndDate;
 
             Playlist.Clear();
             Playlist.AddRange(other.Playlist);
@@ -77,5 +82,6 @@ namespace osu.Game.Online.Multiplayer
 
         public bool ShouldSerializeRoomID() => false;
         public bool ShouldSerializeHost() => false;
+        public bool ShouldSerializeEndDate() => false;
     }
 }

osu.Game/Screens/Multi/Match/Components/Info.cs

@@ -36,7 +36,7 @@ namespace osu.Game.Screens.Multi.Match.Components
         public readonly Bindable<GameType> Type = new Bindable<GameType>();
         public readonly Bindable<IEnumerable<Mod>> Mods = new Bindable<IEnumerable<Mod>>();
 
-        public Info()
+        public Info(Room room)
         {
             RelativeSizeAxes = Axes.X;
             AutoSizeAxes = Axes.Y;
@@ -106,7 +106,7 @@ namespace osu.Game.Screens.Multi.Match.Components
                             Children = new Drawable[]
                             {
                                 viewBeatmapButton = new ViewBeatmapButton(),
-                                readyButton = new ReadyButton
+                                readyButton = new ReadyButton(room)
                                 {
                                     Action = () => OnStart?.Invoke()
                                 }

osu.Game/Screens/Multi/Match/Components/ReadyButton.cs

@@ -1,11 +1,13 @@
 // Copyright (c) 2007-2018 ppy Pty Ltd <contact@ppy.sh>.
 // Licensed under the MIT Licence - https://raw.githubusercontent.com/ppy/osu/master/LICENCE
 
+using System;
 using System.Linq;
 using osu.Framework.Allocation;
 using osu.Framework.Configuration;
 using osu.Framework.Graphics;
 using osu.Game.Beatmaps;
+using osu.Game.Online.Multiplayer;
 using osuTK;
 
 namespace osu.Game.Screens.Multi.Match.Components
@@ -14,11 +16,19 @@ namespace osu.Game.Screens.Multi.Match.Components
     {
         public readonly IBindable<BeatmapInfo> Beatmap = new Bindable<BeatmapInfo>();
 
+        private readonly Room room;
+
+        [Resolved]
+        private IBindableBeatmap gameBeatmap { get; set; }
+
         [Resolved]
         private BeatmapManager beatmaps { get; set; }
 
-        public ReadyButton()
+        private bool hasBeatmap;
+
+        public ReadyButton(Room room)
         {
+            this.room = room;
             RelativeSizeAxes = Axes.Y;
             Size = new Vector2(200, 1);
 
@@ -30,24 +40,43 @@ namespace osu.Game.Screens.Multi.Match.Components
         {
             beatmaps.ItemAdded += beatmapAdded;
 
-            Beatmap.BindValueChanged(updateEnabledState, true);
+            Beatmap.BindValueChanged(updateBeatmap, true);
         }
 
-        private void updateEnabledState(BeatmapInfo beatmap)
+        private void updateBeatmap(BeatmapInfo beatmap)
         {
-            if (beatmap?.OnlineBeatmapID == null)
-            {
-                Enabled.Value = false;
-                return;
-            }
+            hasBeatmap = false;
 
-            Enabled.Value = beatmaps.QueryBeatmap(b => b.OnlineBeatmapID == beatmap.OnlineBeatmapID) != null;
+            if (beatmap?.OnlineBeatmapID == null)
+                return;
+
+            hasBeatmap = beatmaps.QueryBeatmap(b => b.OnlineBeatmapID == beatmap.OnlineBeatmapID) != null;
         }
 
         private void beatmapAdded(BeatmapSetInfo model, bool existing, bool silent)
         {
             if (model.Beatmaps.Any(b => b.OnlineBeatmapID == Beatmap.Value.OnlineBeatmapID))
-                Schedule(() => Enabled.Value = true);
+                Schedule(() => hasBeatmap = true);
+        }
+
+        protected override void Update()
+        {
+            base.Update();
+
+            updateEnabledState();
+        }
+
+        private void updateEnabledState()
+        {
+            if (gameBeatmap.Value == null)
+            {
+                Enabled.Value = false;
+                return;
+            }
+
+            bool hasEnoughTime = DateTimeOffset.UtcNow.AddSeconds(30).AddMilliseconds(gameBeatmap.Value.Track.Length) < room.EndDate;
+
+            Enabled.Value = hasBeatmap && hasEnoughTime;
         }
 
         protected override void Dispose(bool isDisposing)

osu.Game/Screens/Multi/Match/MatchScreen.cs

@@ -79,7 +79,7 @@ namespace osu.Game.Screens.Multi.Match
                     Content = new[]
                     {
                         new Drawable[] { header = new Components.Header { Depth = -1 } },
-                        new Drawable[] { info = new Info { OnStart = onStart } },
+                        new Drawable[] { info = new Info(room) { OnStart = onStart } },
                         new Drawable[]
                         {
                             new GridContainer