Added Button to restore recently deleted beatmaps

osu.Game/Beatmaps/BeatmapManager.cs

@@ -341,6 +341,61 @@ public void Delete(BeatmapSetInfo beatmapSet)
             }
         }
 
+        public void UndeleteAll()
+        {
+            var deleteMaps = QueryBeatmapSets(bs => bs.DeletePending).ToList();
+
+            if (!deleteMaps.Any()) return;
+
+            var notification = new ProgressNotification
+            {
+                CompletionText = "Restored all deleted beatmaps!",
+                Progress = 0,
+                State = ProgressNotificationState.Active,
+            };
+
+            PostNotification?.Invoke(notification);
+
+            int i = 0;
+
+            foreach (var bs in deleteMaps)
+            {
+                if (notification.State == ProgressNotificationState.Cancelled)
+                    // user requested abort
+                    return;
+
+                notification.Text = $"Restoring ({i} of {deleteMaps.Count})";
+                notification.Progress = (float)++i / deleteMaps.Count;
+                Undelete(bs);
+            }
+
+            notification.State = ProgressNotificationState.Completed;
+        }
+
+        public void Undelete(BeatmapSetInfo beatmapSet)
+        {
+            if (beatmapSet.Protected)
+                return;
+
+            lock (importContext)
+            {
+                var context = importContext.Value;
+
+                using (var transaction = context.BeginTransaction())
+                {
+                    context.ChangeTracker.AutoDetectChangesEnabled = false;
+
+                    var iFiles = new FileStore(() => context, storage);
+                    var iBeatmaps = createBeatmapStore(() => context);
+
+                    undelete(iBeatmaps, iFiles, beatmapSet);
+
+                    context.ChangeTracker.AutoDetectChangesEnabled = true;
+                    context.SaveChanges(transaction);
+                }
+            }
+        }
+
         /// <summary>
         /// Delete a beatmap difficulty.
         /// </summary>

osu.Game/Overlays/Settings/Sections/Maintenance/GeneralSettings.cs

@@ -15,6 +15,7 @@ public class GeneralSettings : SettingsSubsection
         private TriangleButton importButton;
         private TriangleButton deleteButton;
         private TriangleButton restoreButton;
+        private TriangleButton undeleteButton;
 
         protected override string Header => "General";
 
@@ -55,6 +56,15 @@ private void load(BeatmapManager beatmaps)
                         }).ContinueWith(t => Schedule(() => restoreButton.Enabled.Value = true));
                     }
                 },
+                undeleteButton = new SettingsButton
+                {
+                    Text = "Restore all recently deleted beatmaps",
+                    Action = () =>
+                    {
+                        undeleteButton.Enabled.Value = false;
+                        Task.Run(() => beatmaps.UndeleteAll()).ContinueWith(t => Schedule(() => undeleteButton.Enabled.Value = true));
+                    }
+                },
             };
         }
     }