Implement some basic serialization and tests

NexusMods.EventSourcing.sln

@@ -30,6 +30,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NexusMods.EventSourcing.Tes
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NexusMods.EventSourcing.Abstractions", "src\NexusMods.EventSourcing.Abstractions\NexusMods.EventSourcing.Abstractions.csproj", "{6737673E-5898-42EC-B0B2-60DE2CFFF0AF}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "NexusMods.EventSourcing.TestModel", "tests\NexusMods.EventSourcing.TestModel\NexusMods.EventSourcing.TestModel.csproj", "{66DCB10E-1D80-4A83-8380-B2E08BEEE7AE}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -39,6 +41,7 @@ Global
 		{A92DED3D-BC67-4E04-9A06-9A1B302B3070} = {0377EBE6-F147-4233-86AD-32C821B9567E}
 		{30CBEB4A-E0C0-4B11-A0CF-F97BFACEEF89} = {6ED01F9D-5E12-4EB2-9601-64A2ADC719DE}
 		{6737673E-5898-42EC-B0B2-60DE2CFFF0AF} = {0377EBE6-F147-4233-86AD-32C821B9567E}
+		{66DCB10E-1D80-4A83-8380-B2E08BEEE7AE} = {6ED01F9D-5E12-4EB2-9601-64A2ADC719DE}
 	EndGlobalSection
 	GlobalSection(ProjectConfigurationPlatforms) = postSolution
 		{A92DED3D-BC67-4E04-9A06-9A1B302B3070}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
@@ -53,5 +56,9 @@ Global
 		{6737673E-5898-42EC-B0B2-60DE2CFFF0AF}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{6737673E-5898-42EC-B0B2-60DE2CFFF0AF}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{6737673E-5898-42EC-B0B2-60DE2CFFF0AF}.Release|Any CPU.Build.0 = Release|Any CPU
+		{66DCB10E-1D80-4A83-8380-B2E08BEEE7AE}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{66DCB10E-1D80-4A83-8380-B2E08BEEE7AE}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{66DCB10E-1D80-4A83-8380-B2E08BEEE7AE}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{66DCB10E-1D80-4A83-8380-B2E08BEEE7AE}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 EndGlobal

src/NexusMods.EventSourcing.Abstractions/DependencyInjectionExtensions.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Reflection;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace NexusMods.EventSourcing.Abstractions;
+
+/// <summary>
+/// DI extensions for the event sourcing library.
+/// </summary>
+public static class DependencyInjectionExtensions
+{
+    /// <summary>
+    /// Registers an event with the service collection.
+    /// </summary>
+    /// <param name="collection"></param>
+    /// <typeparam name="T"></typeparam>
+    /// <returns></returns>
+    public static IServiceCollection AddEvent<T>(this IServiceCollection collection) where T : class, IEvent
+    {
+        var type = typeof(T);
+        var attribute = type.GetCustomAttribute<EventIdAttribute>();
+        if (attribute is null)
+        {
+            throw new ArgumentException($"Event type {type.Name} does not have an EventIdAttribute.");
+        }
+        collection.AddSingleton(s => new EventDefinition(attribute.Guid, type));
+        return collection;
+    }
+
+}

src/NexusMods.EventSourcing.Abstractions/EventDefinition.cs

@@ -0,0 +1,10 @@
+using System;
+
+namespace NexusMods.EventSourcing.Abstractions;
+
+/// <summary>
+/// A record that defines an event and the unique GUID that identifies it.
+/// </summary>
+/// <param name="Guid"></param>
+/// <param name="Type"></param>
+public record EventDefinition(Guid Guid, Type Type);

src/NexusMods.EventSourcing.Abstractions/EventIdAttribute.cs

@@ -0,0 +1,25 @@
+using System;
+
+namespace NexusMods.EventSourcing.Abstractions;
+
+/// <summary>
+/// Marks a an event as having the given GUID id
+/// </summary>
+[AttributeUsage(AttributeTargets.Class)]
+public class EventIdAttribute : Attribute
+{
+    /// <summary>
+    /// The GUID of the entity type.
+    /// </summary>
+    public readonly Guid Guid;
+
+
+    /// <summary>
+    /// Creates a new instance of the <see cref="EventIdAttribute"/> class.
+    /// </summary>
+    /// <param name="guid"></param>
+    public EventIdAttribute(string guid)
+    {
+        Guid = Guid.Parse(guid);
+    }
+}

src/NexusMods.EventSourcing.Abstractions/ISingletonEntity.cs

@@ -0,0 +1,9 @@
+namespace NexusMods.EventSourcing.Abstractions;
+
+/// <summary>
+/// Marks this entity as a singleton entity, the singleton id is used to retrieve the entity from the cache.
+/// </summary>
+public interface ISingletonEntity
+{
+    public static virtual EntityId SingletonId { get; }
+}

src/NexusMods.EventSourcing.Abstractions/NexusMods.EventSourcing.Abstractions.csproj

@@ -5,6 +5,7 @@
 
     <ItemGroup>
       <PackageReference Include="MemoryPack.Core" Version="1.10.0" />
+      <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="6.0.0" />
       <PackageReference Include="TransparentValueObjects" PrivateAssets="all" OutputItemType="Analyzer" ReferenceOutputAssembly="false"/>
     </ItemGroup>
 

src/NexusMods.EventSourcing/EventFormatter.cs

@@ -0,0 +1,46 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using MemoryPack;
+using MemoryPack.Formatters;
+using NexusMods.EventSourcing.Abstractions;
+
+namespace NexusMods.EventSourcing;
+
+public class EventFormatter : MemoryPackFormatter<IEvent>
+{
+    private static Guid _zeroGuid = Guid.Empty;
+    private readonly Dictionary<Guid,Type> _eventByGuid;
+    private readonly Dictionary<Type,Guid> _eventsByType;
+
+    public EventFormatter(IEnumerable<EventDefinition> events)
+    {
+       _eventByGuid = events.ToDictionary(e => e.Guid, e => e.Type);
+       _eventsByType = events.ToDictionary(e => e.Type, e => e.Guid);
+    }
+
+    public override void Serialize<TBufferWriter>(ref MemoryPackWriter<TBufferWriter> writer, scoped ref IEvent? value)
+    {
+        if (value == null)
+        {
+            writer.WriteValue(_zeroGuid);
+            return;
+        }
+
+        var type = value.GetType();
+        writer.WriteValue(_eventsByType[type]);
+        writer.WriteValue(type, (object)value);
+    }
+
+    public override void Deserialize(ref MemoryPackReader reader, scoped ref IEvent? value)
+    {
+        var readValue = reader.ReadValue<Guid>();
+        if (readValue == _zeroGuid)
+        {
+            value = null;
+            return;
+        }
+        var mappedType = _eventByGuid[readValue];
+        value = (IEvent)reader.ReadValue(mappedType)!;
+    }
+}

src/NexusMods.EventSourcing/EventSerializer.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using MemoryPack;
+using MemoryPack.Formatters;
+using NexusMods.EventSourcing.Abstractions;
+
+namespace NexusMods.EventSourcing;
+
+public class EventSerializer
+{
+    public EventSerializer(IEnumerable<EventDefinition> events)
+    {
+        var formatter = new EventFormatter(events);
+        if (!MemoryPackFormatterProvider.IsRegistered<IEvent>())
+            MemoryPackFormatterProvider.Register(formatter);
+    }
+
+    public byte[] Serialize(IEvent @event)
+    {
+        return MemoryPackSerializer.Serialize(@event);
+    }
+
+    public IEvent Deserialize(byte[] data)
+    {
+        return MemoryPackSerializer.Deserialize<IEvent>(data)!;
+    }
+
+}

src/NexusMods.EventSourcing/NexusMods.EventSourcing.csproj

@@ -5,5 +5,11 @@
     <ItemGroup>
       <PackageReference Include="TransparentValueObjects" PrivateAssets="all" OutputItemType="Analyzer" ReferenceOutputAssembly="false"/>
     </ItemGroup>
+    <ItemGroup>
+      <ProjectReference Include="..\NexusMods.EventSourcing.Abstractions\NexusMods.EventSourcing.Abstractions.csproj" />
+    </ItemGroup>
+    <ItemGroup>
+      <Folder Include="Extensions\" />
+    </ItemGroup>
     <Import Project="$([MSBuild]::GetPathOfFileAbove('NuGet.Build.props', '$(MSBuildThisFileDirectory)../'))" />
 </Project>

src/NexusMods.EventSourcing/Services.cs

@@ -0,0 +1,12 @@
+using Microsoft.Extensions.DependencyInjection;
+
+namespace NexusMods.EventSourcing;
+
+public static class Services
+{
+    public static IServiceCollection AddEventSourcing(this IServiceCollection services)
+    {
+        return services.AddSingleton<EventSerializer>();
+    }
+
+}

tests/NexusMods.EventSourcing.TestModel/Events/AddMod.cs

@@ -0,0 +1,36 @@
+using DynamicData;
+using MemoryPack;
+using NexusMods.EventSourcing.Abstractions;
+using NexusMods.EventSourcing.TestModel.Model;
+
+namespace NexusMods.EventSourcing.TestModel.Events;
+
+[EventId("7DC8F80B-50B6-43B7-B805-43450E9F0C2B")]
+[MemoryPackable]
+public partial class AddMod : IEvent
+{
+    public required string Name { get; init; } = string.Empty;
+    public required bool Enabled { get; init; } = true;
+    public required EntityId<Mod> Id { get; init; }
+    public required EntityId<Loadout> Loadout { get; init; }
+
+    public async ValueTask Apply<T>(T context) where T : IEventContext
+    {
+        var loadout = await context.Retrieve(Loadout);
+        var mod = new Mod
+        {
+            Id = Id.Value,
+            Name = Name,
+            Enabled = Enabled,
+        };
+        loadout._mods.AddOrUpdate(mod);
+        context.AttachEntity(Id, mod);
+
+    }
+
+    public void ModifiedEntities(Action<EntityId> handler)
+    {
+        handler(Id.Value);
+        handler(Loadout.Value);
+    }
+}

tests/NexusMods.EventSourcing.TestModel/Events/CreateLoadout.cs

@@ -0,0 +1,35 @@
+using DynamicData;
+using MemoryPack;
+using NexusMods.EventSourcing.Abstractions;
+using NexusMods.EventSourcing.TestModel.Model;
+
+namespace NexusMods.EventSourcing.TestModel.Events;
+
+[EventId("63A4CB90-27E2-468A-BE94-CB01A38D8C09")]
+[MemoryPackable]
+public partial class CreateLoadout : IEvent
+{
+    public required string Name { get; init; }
+
+    public required EntityId<Loadout> Id { get; init; }
+
+
+    public async ValueTask Apply<T>(T context) where T : IEventContext
+    {
+        var registry = await context.Retrieve(LoadoutRegistry.StaticId);
+        var loadout = new Loadout
+        {
+            Id = Id.Value,
+            Name = Name
+        };
+        registry._loadouts.AddOrUpdate(loadout);
+        context.AttachEntity(Id, loadout);
+    }
+
+    public static CreateLoadout Create(string name) => new() { Name = name, Id = EntityId<Loadout>.NewId() };
+
+    public void ModifiedEntities(Action<EntityId> handler)
+    {
+        handler(Id.Value);
+    }
+}

tests/NexusMods.EventSourcing.TestModel/Events/SwapModEnabled.cs

@@ -0,0 +1,29 @@
+using MemoryPack;
+using NexusMods.EventSourcing.Abstractions;
+using NexusMods.EventSourcing.TestModel.Model;
+
+namespace NexusMods.EventSourcing.TestModel.Events;
+
+[EventId("8492075A-DED5-42BF-8D01-B4CDCE2526CF")]
+[MemoryPackable]
+public partial class SwapModEnabled : IEvent
+{
+    public required EntityId<Mod> Id { get; init; }
+    public async ValueTask Apply<T>(T context) where T : IEventContext
+    {
+        var mod = await context.Retrieve(Id);
+        mod.Enabled = !mod.Enabled;
+    }
+
+    /// <summary>
+    /// Helper method to create a new event instance.
+    /// </summary>
+    /// <param name="id"></param>
+    /// <returns></returns>
+    public static SwapModEnabled Create(EntityId<Mod> id) => new() { Id = id };
+
+    public void ModifiedEntities(Action<EntityId> handler)
+    {
+        handler(Id.Value);
+    }
+}

tests/NexusMods.EventSourcing.TestModel/Model/Collection.cs

@@ -0,0 +1,26 @@
+using System.Collections.ObjectModel;
+using DynamicData;
+using NexusMods.EventSourcing.Abstractions;
+using ReactiveUI.Fody.Helpers;
+
+namespace NexusMods.EventSourcing.TestModel.Model;
+
+public class Collection
+{
+    public Loadout Loadout { get; internal set; } = null!;
+
+    internal SourceCache<Mod, EntityId> _mods = new(x => x.Id);
+
+    private ReadOnlyObservableCollection<Mod> _modsConnected = null!;
+    public ReadOnlyObservableCollection<Mod> Mods { get; internal set; } = null!;
+
+    [Reactive]
+    public string Name { get; internal set; } = string.Empty;
+
+    public Collection()
+    {
+        _mods.Connect()
+            .Bind(out _modsConnected)
+            .Subscribe();
+    }
+}

tests/NexusMods.EventSourcing.TestModel/Model/Loadout.cs

@@ -0,0 +1,13 @@
+using DynamicData;
+using NexusMods.EventSourcing.Abstractions;
+
+namespace NexusMods.EventSourcing.TestModel.Model;
+
+public class Loadout : IEntity
+{
+    public EntityId Id { get; internal set; }
+
+    public string Name { get; internal set; } = string.Empty;
+
+    internal SourceCache<Mod, EntityId> _mods = new(x => x.Id);
+}

tests/NexusMods.EventSourcing.TestModel/Model/LoadoutRegistry.cs

@@ -0,0 +1,24 @@
+using System.Collections.ObjectModel;
+using DynamicData;
+using NexusMods.EventSourcing.Abstractions;
+
+namespace NexusMods.EventSourcing.TestModel.Model;
+
+public class LoadoutRegistry : IEntity
+{
+    internal readonly SourceCache<Loadout, EntityId> _loadouts = new(x => x.Id);
+
+    private ReadOnlyObservableCollection<Loadout> _loadoutsConnected;
+    public ReadOnlyObservableCollection<Loadout> Loadouts => _loadoutsConnected;
+
+    public LoadoutRegistry()
+    {
+        _loadouts.Connect()
+            .Bind(out _loadoutsConnected)
+            .Subscribe();
+    }
+
+    public static EntityId<LoadoutRegistry> StaticId = new(EntityId.From(Guid.Parse("7F3E3745-51B9-44CB-BBDA-B1555191330E")));
+
+    public EntityId Id { get; } = StaticId.Value;
+}