Merge pull request #440 from MUnique/dev/guidv7

Implemented UUID V7 for primary key values

src/GameLogic/MiniGames/MiniGameContext.cs

@@ -494,7 +494,7 @@ protected async ValueTask SaveRankingAsync(IEnumerable<(int Rank, Character Char
         try
         {
             using var context = this._gameContext.PersistenceContextProvider.CreateNewTypedContext<MiniGameRankingEntry>(false);
-            var instanceId = Guid.NewGuid();
+            var instanceId = GuidV7.NewGuid();
             var timestamp = DateTime.UtcNow;
             foreach (var score in scoreEntries)
             {

src/Persistence/EntityFramework/EntityDataContext.cs

@@ -79,6 +79,7 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
             if (key != null)
             {
                 key.ValueGenerated = Microsoft.EntityFrameworkCore.Metadata.ValueGenerated.OnAdd;
+                key.SetValueGeneratorFactory((_, _) => new GuidV7ValueGenerator());
             }
         }
 

src/Persistence/EntityFramework/GuidV7ValueGenerator.cs

@@ -0,0 +1,23 @@
+// <copyright file="GuidV7ValueGenerator.cs" company="MUnique">
+// Licensed under the MIT License. See LICENSE file in the project root for full license information.
+// </copyright>
+
+namespace MUnique.OpenMU.Persistence.EntityFramework;
+
+using Microsoft.EntityFrameworkCore.ChangeTracking;
+using Microsoft.EntityFrameworkCore.ValueGeneration;
+
+/// <summary>
+/// A value generator for UUID V7 used as primary key.
+/// </summary>
+public class GuidV7ValueGenerator : ValueGenerator<Guid>
+{
+    /// <inheritdoc/>
+    public override bool GeneratesTemporaryValues => false;
+
+    /// <inheritdoc/>
+    public override Guid Next(EntityEntry entry)
+    {
+        return GuidV7.NewGuid();
+    }
+}

src/Persistence/GuidV7.cs

@@ -0,0 +1,48 @@
+// <copyright file="GuidV7.cs" company="MUnique">
+// Licensed under the MIT License. See LICENSE file in the project root for full license information.
+// </copyright>
+
+namespace MUnique.OpenMU.Persistence;
+
+using System.Security.Cryptography;
+
+/// <summary>
+/// A generator for version 7 GUIDs. Layout:
+/// The first 6 bytes is a unix timestamp in milliseconds.
+/// The 7th byte contains the version number (7) in the upper 4 bits.
+/// The rest is random.
+/// </summary>
+public static class GuidV7
+{
+    /// <summary>
+    /// Creates a new random guid.
+    /// </summary>
+    /// <returns>The new guid.</returns>
+    public static Guid NewGuid() => NewGuid(DateTimeOffset.UtcNow);
+
+    /// <summary>
+    /// Creates a new random guid for the specified date.
+    /// </summary>
+    /// <param name="dateTimeOffset">The date time offset which is the prefix of the id.</param>
+    /// <returns>The new guid.</returns>
+    public static Guid NewGuid(DateTimeOffset dateTimeOffset)
+    {
+        // We create a buffer which is two bytes bigger than the Guid,
+        // because we don't need the first two bytes of the timestamp.
+        Span<byte> buffer = stackalloc byte[18];
+        var uuidAsBytes = buffer[2..];
+        var currentTimestamp = dateTimeOffset.ToUnixTimeMilliseconds();
+
+        if (!BitConverter.TryWriteBytes(buffer, currentTimestamp))
+        {
+            throw new InvalidOperationException("Could not convert the timestamp to bytes.");
+        }
+
+        RandomNumberGenerator.Fill(uuidAsBytes[6..]);
+
+        uuidAsBytes[6] &= 0x0F;
+        uuidAsBytes[6] |= 0x70;
+
+        return new Guid(uuidAsBytes, true);
+    }
+}

src/Persistence/InMemory/InMemoryContext.cs

@@ -44,7 +44,10 @@ public void Dispose()
         this.SavedChanges = null;
     }
 
-    /// <inheritdoc/>
+    /// <summary>
+    /// Saves the changes of the context.
+    /// </summary>
+    /// <returns><c>True</c>, if the saving was successful; <c>false</c>, otherwise.</returns>
     public bool SaveChanges()
     {
         foreach (var repository in this.Provider.MemoryRepositories)
@@ -98,7 +101,7 @@ public T CreateNew<T>(params object?[] args)
         {
             if (identifiable.Id == Guid.Empty)
             {
-                identifiable.Id = Guid.NewGuid();
+                identifiable.Id = GuidV7.NewGuid();
             }
 
             var repository = this.Provider.GetRepository<T>() as IMemoryRepository;
@@ -116,7 +119,7 @@ public object CreateNew(Type type, params object?[] args)
         {
             if (identifiable.Id == Guid.Empty)
             {
-                identifiable.Id = Guid.NewGuid();
+                identifiable.Id = GuidV7.NewGuid();
             }
 
             var repository = this.Provider.GetRepository(type) as IMemoryRepository;