Add RealmLive implementation

osu.Game.Tests/Database/RealmLiveTests.cs

@@ -0,0 +1,199 @@
+// 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 System.Diagnostics;
+using System.Linq;
+using System.Threading.Tasks;
+using NUnit.Framework;
+using osu.Game.Database;
+using osu.Game.Models;
+using Realms;
+
+#nullable enable
+
+namespace osu.Game.Tests.Database
+{
+    public class RealmLiveTests : RealmTest
+    {
+        [Test]
+        public void TestValueAccessWithOpenContext()
+        {
+            RunTestWithRealm((realmFactory, _) =>
+            {
+                RealmLive<RealmBeatmap>? liveBeatmap = null;
+                Task.Factory.StartNew(() =>
+                {
+                    using (var threadContext = realmFactory.CreateContext())
+                    {
+                        var beatmap = threadContext.Write(r => r.Add(new RealmBeatmap(CreateRuleset(), new RealmBeatmapDifficulty(), new RealmBeatmapMetadata())));
+
+                        liveBeatmap = beatmap.ToLive();
+                    }
+                }, TaskCreationOptions.LongRunning | TaskCreationOptions.HideScheduler).Wait();
+
+                Debug.Assert(liveBeatmap != null);
+
+                Task.Factory.StartNew(() =>
+                {
+                    Assert.DoesNotThrow(() =>
+                    {
+                        using (realmFactory.CreateContext())
+                        {
+                            var resolved = liveBeatmap.Value;
+
+                            Assert.IsTrue(resolved.Realm.IsClosed);
+                            Assert.IsTrue(resolved.IsValid);
+
+                            // can access properties without a crash.
+                            Assert.IsFalse(resolved.Hidden);
+                        }
+                    });
+                }, TaskCreationOptions.LongRunning | TaskCreationOptions.HideScheduler).Wait();
+            });
+        }
+
+        [Test]
+        public void TestScopedReadWithoutContext()
+        {
+            RunTestWithRealm((realmFactory, _) =>
+            {
+                RealmLive<RealmBeatmap>? liveBeatmap = null;
+                Task.Factory.StartNew(() =>
+                {
+                    using (var threadContext = realmFactory.CreateContext())
+                    {
+                        var beatmap = threadContext.Write(r => r.Add(new RealmBeatmap(CreateRuleset(), new RealmBeatmapDifficulty(), new RealmBeatmapMetadata())));
+
+                        liveBeatmap = beatmap.ToLive();
+                    }
+                }, TaskCreationOptions.LongRunning | TaskCreationOptions.HideScheduler).Wait();
+
+                Debug.Assert(liveBeatmap != null);
+
+                Task.Factory.StartNew(() =>
+                {
+                    liveBeatmap.PerformRead(beatmap =>
+                    {
+                        Assert.IsTrue(beatmap.IsValid);
+                        Assert.IsFalse(beatmap.Hidden);
+                    });
+                }, TaskCreationOptions.LongRunning | TaskCreationOptions.HideScheduler).Wait();
+            });
+        }
+
+        [Test]
+        public void TestScopedWriteWithoutContext()
+        {
+            RunTestWithRealm((realmFactory, _) =>
+            {
+                RealmLive<RealmBeatmap>? liveBeatmap = null;
+                Task.Factory.StartNew(() =>
+                {
+                    using (var threadContext = realmFactory.CreateContext())
+                    {
+                        var beatmap = threadContext.Write(r => r.Add(new RealmBeatmap(CreateRuleset(), new RealmBeatmapDifficulty(), new RealmBeatmapMetadata())));
+
+                        liveBeatmap = beatmap.ToLive();
+                    }
+                }, TaskCreationOptions.LongRunning | TaskCreationOptions.HideScheduler).Wait();
+
+                Debug.Assert(liveBeatmap != null);
+
+                Task.Factory.StartNew(() =>
+                {
+                    liveBeatmap.PerformWrite(beatmap => { beatmap.Hidden = true; });
+                    liveBeatmap.PerformRead(beatmap => { Assert.IsTrue(beatmap.Hidden); });
+                }, TaskCreationOptions.LongRunning | TaskCreationOptions.HideScheduler).Wait();
+            });
+        }
+
+        [Test]
+        public void TestValueAccessWithoutOpenContextFails()
+        {
+            RunTestWithRealm((realmFactory, _) =>
+            {
+                RealmLive<RealmBeatmap>? liveBeatmap = null;
+                Task.Factory.StartNew(() =>
+                {
+                    using (var threadContext = realmFactory.CreateContext())
+                    {
+                        var beatmap = threadContext.Write(r => r.Add(new RealmBeatmap(CreateRuleset(), new RealmBeatmapDifficulty(), new RealmBeatmapMetadata())));
+
+                        liveBeatmap = beatmap.ToLive();
+                    }
+                }, TaskCreationOptions.LongRunning | TaskCreationOptions.HideScheduler).Wait();
+
+                Debug.Assert(liveBeatmap != null);
+
+                Task.Factory.StartNew(() =>
+                {
+                    Assert.Throws<InvalidOperationException>(() =>
+                    {
+                        var unused = liveBeatmap.Value;
+                    });
+                }, TaskCreationOptions.LongRunning | TaskCreationOptions.HideScheduler).Wait();
+            });
+        }
+
+        [Test]
+        public void TestLiveAssumptions()
+        {
+            RunTestWithRealm((realmFactory, _) =>
+            {
+                int changesTriggered = 0;
+
+                using (var updateThreadContext = realmFactory.CreateContext())
+                {
+                    updateThreadContext.All<RealmBeatmap>().SubscribeForNotifications(gotChange);
+                    RealmLive<RealmBeatmap>? liveBeatmap = null;
+
+                    Task.Factory.StartNew(() =>
+                    {
+                        using (var threadContext = realmFactory.CreateContext())
+                        {
+                            var ruleset = CreateRuleset();
+                            var beatmap = threadContext.Write(r => r.Add(new RealmBeatmap(ruleset, new RealmBeatmapDifficulty(), new RealmBeatmapMetadata())));
+
+                            // add a second beatmap to ensure that a full refresh occurs below.
+                            // not just a refresh from the resolved Live.
+                            threadContext.Write(r => r.Add(new RealmBeatmap(ruleset, new RealmBeatmapDifficulty(), new RealmBeatmapMetadata())));
+
+                            liveBeatmap = beatmap.ToLive();
+                        }
+                    }, TaskCreationOptions.LongRunning | TaskCreationOptions.HideScheduler).Wait();
+
+                    Debug.Assert(liveBeatmap != null);
+
+                    // not yet seen by main context
+                    Assert.AreEqual(0, updateThreadContext.All<RealmBeatmap>().Count());
+                    Assert.AreEqual(0, changesTriggered);
+
+                    var resolved = liveBeatmap.Value;
+
+                    // retrieval causes an implicit refresh. even changes that aren't related to the retrieval are fired at this point.
+                    Assert.AreEqual(2, updateThreadContext.All<RealmBeatmap>().Count());
+                    Assert.AreEqual(1, changesTriggered);
+
+                    // even though the realm that this instance was resolved for was closed, it's still valid.
+                    Assert.IsTrue(resolved.Realm.IsClosed);
+                    Assert.IsTrue(resolved.IsValid);
+
+                    // can access properties without a crash.
+                    Assert.IsFalse(resolved.Hidden);
+
+                    updateThreadContext.Write(r =>
+                    {
+                        // can use with the main context.
+                        r.Remove(resolved);
+                    });
+                }
+
+                void gotChange(IRealmCollection<RealmBeatmap> sender, ChangeSet changes, Exception error)
+                {
+                    changesTriggered++;
+                }
+            });
+        }
+    }
+}

osu.Game/Database/RealmLive.cs

@@ -0,0 +1,111 @@
+// 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 System.Threading;
+using Realms;
+
+#nullable enable
+
+namespace osu.Game.Database
+{
+    /// <summary>
+    /// Provides a method of working with realm objects over longer application lifetimes.
+    /// </summary>
+    /// <typeparam name="T">The underlying object type.</typeparam>
+    public class RealmLive<T> : ILive<T> where T : RealmObject, IHasGuidPrimaryKey
+    {
+        public Guid ID { get; }
+
+        private readonly SynchronizationContext? fetchedContext;
+        private readonly int fetchedThreadId;
+
+        /// <summary>
+        /// The original live data used to create this instance.
+        /// </summary>
+        private readonly T data;
+
+        /// <summary>
+        /// Construct a new instance of live realm data.
+        /// </summary>
+        /// <param name="data">The realm data.</param>
+        public RealmLive(T data)
+        {
+            this.data = data;
+
+            fetchedContext = SynchronizationContext.Current;
+            fetchedThreadId = Thread.CurrentThread.ManagedThreadId;
+
+            ID = data.ID;
+        }
+
+        /// <summary>
+        /// Perform a read operation on this live object.
+        /// </summary>
+        /// <param name="perform">The action to perform.</param>
+        public void PerformRead(Action<T> perform)
+        {
+            if (originalDataValid)
+            {
+                perform(data);
+                return;
+            }
+
+            using (var realm = Realm.GetInstance(data.Realm.Config))
+                perform(realm.Find<T>(ID));
+        }
+
+        /// <summary>
+        /// Perform a read operation on this live object.
+        /// </summary>
+        /// <param name="perform">The action to perform.</param>
+        public TReturn PerformRead<TReturn>(Func<T, TReturn> perform)
+        {
+            if (typeof(RealmObjectBase).IsAssignableFrom(typeof(TReturn)))
+                throw new InvalidOperationException($"Realm live objects should not exit the scope of {nameof(PerformRead)}.");
+
+            if (originalDataValid)
+                return perform(data);
+
+            using (var realm = Realm.GetInstance(data.Realm.Config))
+                return perform(realm.Find<T>(ID));
+        }
+
+        /// <summary>
+        /// Perform a write operation on this live object.
+        /// </summary>
+        /// <param name="perform">The action to perform.</param>
+        public void PerformWrite(Action<T> perform) =>
+            PerformRead(t =>
+            {
+                var transaction = t.Realm.BeginWrite();
+                perform(t);
+                transaction.Commit();
+            });
+
+        public T Value
+        {
+            get
+            {
+                if (originalDataValid)
+                    return data;
+
+                T retrieved;
+
+                using (var realm = Realm.GetInstance(data.Realm.Config))
+                    retrieved = realm.Find<T>(ID);
+
+                if (!retrieved.IsValid)
+                    throw new InvalidOperationException("Attempted to access value without an open context");
+
+                return retrieved;
+            }
+        }
+
+        private bool originalDataValid => isCorrectThread && data.IsValid && !data.Realm.IsClosed;
+
+        // this matches realm's internal thread validation (see https://github.com/realm/realm-dotnet/blob/903b4d0b304f887e37e2d905384fb572a6496e70/Realm/Realm/Native/SynchronizationContextScheduler.cs#L72)
+        private bool isCorrectThread
+            => (fetchedContext != null && SynchronizationContext.Current == fetchedContext) || fetchedThreadId == Thread.CurrentThread.ManagedThreadId;
+    }
+}

osu.Game/Database/RealmObjectExtensions.cs

@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System.Collections.Generic;
+using System.Linq;
 using AutoMapper;
 using osu.Game.Input.Bindings;
 using Realms;
@@ -47,5 +48,17 @@ namespace osu.Game.Database
 
             return mapper.Map<T>(item);
         }
+
+        public static List<RealmLive<T>> ToLive<T>(this IEnumerable<T> realmList)
+            where T : RealmObject, IHasGuidPrimaryKey
+        {
+            return realmList.Select(l => new RealmLive<T>(l)).ToList();
+        }
+
+        public static RealmLive<T> ToLive<T>(this T realmObject)
+            where T : RealmObject, IHasGuidPrimaryKey
+        {
+            return new RealmLive<T>(realmObject);
+        }
     }
 }