hopefully not a horribly foolish refactoring

Femto.Common/Infrastructure/SaveChangesPipelineBehaviour.cs

@@ -0,0 +1,57 @@
+using Femto.Common.Domain;
+using MediatR;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+
+namespace Femto.Common.Infrastructure;
+
+public class SaveChangesPipelineBehaviour<TRequest, TResponse>(
+    DbContext context,
+    IPublisher publisher,
+    ILogger<SaveChangesPipelineBehaviour<TRequest, TResponse>> logger
+) : IPipelineBehavior<TRequest, TResponse>
+    where TRequest : notnull
+{
+    public async Task<TResponse> Handle(
+        TRequest request,
+        RequestHandlerDelegate<TResponse> next,
+        CancellationToken cancellationToken
+    )
+    {
+        var response = await next(cancellationToken);
+
+        if (context.ChangeTracker.HasChanges())
+        {
+            await this.EmitDomainEvents(cancellationToken);
+
+            logger.LogDebug("saving changes");
+            await context.SaveChangesAsync(cancellationToken);
+        }
+        return response;
+    }
+
+    private async Task EmitDomainEvents(CancellationToken cancellationToken)
+    {
+        var domainEvents = context
+            .ChangeTracker.Entries<Entity>()
+            .SelectMany(e =>
+            {
+                var events = e.Entity.DomainEvents;
+                e.Entity.ClearDomainEvents();
+                return events;
+            })
+            .ToList();
+
+        logger.LogTrace("loaded {Count} domain events", domainEvents.Count);
+
+        foreach (var domainEvent in domainEvents)
+        {
+            logger.LogTrace(
+                "publishing {Type} domain event {Id}",
+                domainEvent.GetType().Name,
+                domainEvent.EventId
+            );
+            await publisher.Publish(domainEvent, cancellationToken);
+        }
+    }
+}