Add IBeatmapInfo equality support

osu.Game/Beatmaps/BeatmapInfo.cs

@@ -151,6 +151,17 @@ namespace osu.Game.Beatmaps
 
         public override string ToString() => this.GetDisplayTitle();
 
+        public bool Equals(IBeatmapInfo other)
+        {
+            if (other is BeatmapInfo b)
+                return Equals(b);
+
+            if (OnlineID > 0 && other?.OnlineID > 0)
+                return other.OnlineID == OnlineID;
+
+            return false;
+        }
+
         public bool Equals(BeatmapInfo other)
         {
             if (ID == 0 || other?.ID == 0)

osu.Game/Beatmaps/IBeatmapInfo.cs

@@ -1,6 +1,7 @@
 // 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;
 using osu.Game.Database;
 using osu.Game.Rulesets;
 
@@ -11,7 +12,7 @@ namespace osu.Game.Beatmaps
     /// <summary>
     /// A single beatmap difficulty.
     /// </summary>
-    public interface IBeatmapInfo : IHasOnlineID<int>
+    public interface IBeatmapInfo : IHasOnlineID<int>, IEquatable<IBeatmapInfo>
     {
         /// <summary>
         /// The user-specified name given to this beatmap.

osu.Game/Models/RealmBeatmap.cs

@@ -98,6 +98,21 @@ namespace osu.Game.Models
 
         #endregion
 
+        #region Implementation of IEquatable<IBeatmapInfo>
+
+        public bool Equals(IBeatmapInfo? other)
+        {
+            if (other is RealmBeatmap b)
+                return b.ID == ID;
+
+            if (OnlineID > 0 && other?.OnlineID > 0)
+                return other.OnlineID == OnlineID;
+
+            return false;
+        }
+
+        #endregion
+
         public bool AudioEquals(RealmBeatmap? other) => other != null
                                                         && BeatmapSet != null
                                                         && other.BeatmapSet != null

osu.Game/Online/API/Requests/Responses/APIBeatmap.cs

@@ -103,5 +103,17 @@ namespace osu.Game.Online.API.Requests.Responses
         public string Hash => throw new NotImplementedException();
 
         #endregion
+
+        #region Implementation of IEquatable<IBeatmapInfo>
+
+        public bool Equals(IBeatmapInfo? other)
+        {
+            if (OnlineID > 0 && other?.OnlineID > 0)
+                return other.OnlineID == OnlineID;
+
+            return false;
+        }
+
+        #endregion
     }
 }