Make an interface for beatmaps

osu.Game/Beatmaps/Beatmap.cs

@@ -12,47 +12,52 @@ using osu.Game.IO.Serialization.Converters;
 
 namespace osu.Game.Beatmaps
 {
-    /// <summary>
+    public interface IBeatmap : IJsonSerializable
-    /// A Beatmap containing converted HitObjects.
-    /// </summary>
-    public class Beatmap<T> : IJsonSerializable
-        where T : HitObject
     {
-        public BeatmapInfo BeatmapInfo = new BeatmapInfo();
+        /// <summary>
-        public ControlPointInfo ControlPointInfo = new ControlPointInfo();
+        /// This beatmap's info.
-        public List<BreakPeriod> Breaks = new List<BreakPeriod>();
+        /// </summary>
-
+        BeatmapInfo BeatmapInfo { get; }
-        [JsonIgnore]
-        public BeatmapMetadata Metadata => BeatmapInfo?.Metadata ?? BeatmapInfo?.BeatmapSet?.Metadata;
 
         /// <summary>
-        /// The HitObjects this Beatmap contains.
+        /// This beatmap's metadata.
         /// </summary>
-        [JsonConverter(typeof(TypedListConverter<HitObject>))]
+        BeatmapMetadata Metadata { get; }
-        public List<T> HitObjects = new List<T>();
+
+        /// <summary>
+        /// The control points in this beatmap.
+        /// </summary>
+        ControlPointInfo ControlPointInfo { get; }
+
+        /// <summary>
+        /// The breaks in this beatmap.
+        /// </summary>
+        List<BreakPeriod> Breaks { get; }
 
         /// <summary>
         /// Total amount of break time in the beatmap.
         /// </summary>
-        [JsonIgnore]
+        double TotalBreakTime { get; }
-        public double TotalBreakTime => Breaks.Sum(b => b.Duration);
 
         /// <summary>
-        /// Constructs a new beatmap.
+        /// The hitobjects contained by this beatmap.
         /// </summary>
-        /// <param name="original">The original beatmap to use the parameters of.</param>
+        IEnumerable<HitObject> HitObjects { get; }
-        public Beatmap(Beatmap<T> original = null)
-        {
-            BeatmapInfo = original?.BeatmapInfo.DeepClone() ?? BeatmapInfo;
-            ControlPointInfo = original?.ControlPointInfo ?? ControlPointInfo;
-            Breaks = original?.Breaks ?? Breaks;
-            HitObjects = original?.HitObjects ?? HitObjects;
 
-            if (original == null && Metadata == null)
+        /// <summary>
+        /// Creates a shallow-clone of this beatmap and returns it.
+        /// </summary>
+        /// <returns>The shallow-cloned beatmap.</returns>
+        IBeatmap Clone();
+    }
+
+    /// <summary>
+    /// A Beatmap containing converted HitObjects.
+    /// </summary>
+    public class Beatmap<T> : IBeatmap
+        where T : HitObject
     {
-                // we may have no metadata in cases we weren't sourced from the database.
+        public BeatmapInfo BeatmapInfo { get; set; } = new BeatmapInfo
-                // let's fill it (and other related fields) so we don't need to null-check it in future usages.
-                BeatmapInfo = new BeatmapInfo
         {
             Metadata = new BeatmapMetadata
             {
@@ -63,26 +68,41 @@ namespace osu.Game.Beatmaps
             Version = @"Normal",
             BaseDifficulty = new BeatmapDifficulty()
         };
-            }
+
-        }
+        [JsonIgnore]
-    }
+        public BeatmapMetadata Metadata => BeatmapInfo?.Metadata ?? BeatmapInfo?.BeatmapSet?.Metadata;
+
+        public ControlPointInfo ControlPointInfo { get; set; } = new ControlPointInfo();
+
+        public List<BreakPeriod> Breaks { get; set; } = new List<BreakPeriod>();
 
         /// <summary>
-    /// A Beatmap containing un-converted HitObjects.
+        /// Total amount of break time in the beatmap.
         /// </summary>
+        [JsonIgnore]
+        public double TotalBreakTime => Breaks.Sum(b => b.Duration);
+
+        /// <summary>
+        /// The HitObjects this Beatmap contains.
+        /// </summary>
+        [JsonConverter(typeof(TypedListConverter<HitObject>))]
+        public List<T> HitObjects = new List<T>();
+
+        IEnumerable<HitObject> IBeatmap.HitObjects => HitObjects;
+
+        public Beatmap<T> Clone() => new Beatmap<T>
+        {
+            BeatmapInfo = BeatmapInfo.DeepClone(),
+            ControlPointInfo = ControlPointInfo,
+            Breaks = Breaks,
+            HitObjects = HitObjects
+        };
+
+        IBeatmap IBeatmap.Clone() => Clone();
+    }
+
     public class Beatmap : Beatmap<HitObject>
     {
-        /// <summary>
+        public new Beatmap Clone() => (Beatmap)base.Clone();
-        /// Constructs a new beatmap.
-        /// </summary>
-        /// <param name="original">The original beatmap to use the parameters of.</param>
-        public Beatmap(Beatmap original)
-            : base(original)
-        {
-        }
-
-        public Beatmap()
-        {
-        }
     }
 }

osu.Game/Beatmaps/BeatmapConverter.cs

@@ -37,7 +37,7 @@ namespace osu.Game.Beatmaps
         public Beatmap<T> Convert(Beatmap original)
         {
             // We always operate on a clone of the original beatmap, to not modify it game-wide
-            return ConvertBeatmap(new Beatmap(original));
+            return ConvertBeatmap(original.Clone());
         }
 
         void IBeatmapConverter.Convert(Beatmap original) => Convert(original);

osu.Game/Beatmaps/Legacy/LegacyBeatmap.cs

@@ -8,14 +8,5 @@ namespace osu.Game.Beatmaps.Legacy
     /// </summary>
     public class LegacyBeatmap : Beatmap
     {
-        /// <summary>
-        /// Constructs a new beatmap.
-        /// </summary>
-        /// <param name="original">The original beatmap to use the parameters of.</param>
-        internal LegacyBeatmap(Beatmap original = null)
-            : base(original)
-        {
-            HitObjects = original?.HitObjects;
-        }
     }
 }

osu.Game/Screens/Play/BreakOverlay.cs

@@ -18,11 +18,11 @@ namespace osu.Game.Screens.Play
         private const float remaining_time_container_max_size = 0.3f;
         private const int vertical_margin = 25;
 
-        private List<BreakPeriod> breaks;
+        private IReadOnlyList<BreakPeriod> breaks;
 
         private readonly Container fadeContainer;
 
-        public List<BreakPeriod> Breaks
+        public IReadOnlyList<BreakPeriod> Breaks
         {
             get => breaks;
             set

osu.Game/Tests/Beatmaps/TestBeatmap.cs

@@ -12,8 +12,14 @@ namespace osu.Game.Tests.Beatmaps
     public class TestBeatmap : Beatmap
     {
         public TestBeatmap(RulesetInfo ruleset)
-        : base(createTestBeatmap())
         {
+            var baseBeatmap = createTestBeatmap();
+
+            BeatmapInfo = baseBeatmap.BeatmapInfo;
+            ControlPointInfo = baseBeatmap.ControlPointInfo;
+            Breaks = baseBeatmap.Breaks;
+            HitObjects = baseBeatmap.HitObjects;
+
             BeatmapInfo.Ruleset = ruleset;
         }