Synchronous in-memory EventBus.

lib/Logitar.EventSourcing.Infrastructure/DependencyInjectionExtensions.cs

@@ -14,6 +14,8 @@ public static class DependencyInjectionExtensions
   /// <returns>The dependency container.</returns>
   public static IServiceCollection AddLogitarEventSourcingInfrastructure(this IServiceCollection services)
   {
-    return services.AddSingleton<IEventSerializer, EventSerializer>();
+    return services
+      .AddSingleton<IEventSerializer, EventSerializer>()
+      .AddScoped<IEventBus, EventBus>();
   }
 }

lib/Logitar.EventSourcing.Infrastructure/EventBus.cs

@@ -0,0 +1,51 @@
+using Microsoft.Extensions.DependencyInjection;
+using System.Reflection;
+
+namespace Logitar.EventSourcing.Infrastructure;
+
+/// <summary>
+/// Implements an in-memory event bus into which published events are handled synchronously.
+/// </summary>
+public class EventBus : IEventBus
+{
+  /// <summary>
+  /// Gets the service provider.
+  /// </summary>
+  protected IServiceProvider ServiceProvider { get; }
+
+  /// <summary>
+  /// Initializes a new instance of the <see cref="EventBus"/> class.
+  /// </summary>
+  /// <param name="serviceProvider">The service provider.</param>
+  public EventBus(IServiceProvider serviceProvider)
+  {
+    ServiceProvider = serviceProvider;
+  }
+
+  /// <summary>
+  /// Publishes the specified event to the event bus.
+  /// </summary>
+  /// <param name="event">The event to publish.</param>
+  /// <param name="cancellationToken">The cancellation token.</param>
+  /// <returns>The asynchronous operation.</returns>
+  public async Task PublishAsync(IEvent @event, CancellationToken cancellationToken)
+  {
+    IEnumerable<object?> handlers = ServiceProvider.GetServices(typeof(IEventHandler<>).MakeGenericType(@event.GetType()));
+    if (handlers.Any())
+    {
+      Type[] parameterTypes = [@event.GetType(), typeof(CancellationToken)];
+      object[] parameters = [@event, cancellationToken];
+      foreach (object? handler in handlers)
+      {
+        if (handler is not null)
+        {
+          MethodInfo? handle = handler.GetType().GetMethod(nameof(IEventHandler<>.HandleAsync), parameterTypes);
+          if (handle is not null)
+          {
+            await (Task)handle.Invoke(handler, parameters)!;
+          }
+        }
+      }
+    }
+  }
+}

lib/Logitar.EventSourcing.Infrastructure/IEventBus.cs

@@ -11,6 +11,5 @@ public interface IEventBus
   /// <param name="event">The event to publish.</param>
   /// <param name="cancellationToken">The cancellation token.</param>
   /// <returns>The asynchronous operation.</returns>
-
   Task PublishAsync(IEvent @event, CancellationToken cancellationToken = default);
 }