register-referentie/services/projection-api/Projection.ReadModel/EfNotificationLog.cs

using EventSubscriber.Application;
using Microsoft.EntityFrameworkCore;

namespace Projection.ReadModel;

/// <summary>EF Core implementation of the notification log. Idempotency is enforced atomically
/// by the primary key on <c>key</c>: a duplicate insert raises a unique violation, which is
/// caught and reported as "already recorded" rather than failing the request.</summary>
public sealed class EfNotificationLog(ProjectionDbContext db) : INotificationLog
{
    public async Task<bool> TryRecordAsync(RecordedNotification notification, CancellationToken ct = default)
    {
        db.ProcessedNotifications.Add(new ProcessedNotificationRow
        {
            Key = notification.Key,
            Actie = notification.Actie,
            ZaakId = notification.ZaakId,
            Resource = notification.Resource,
            ReceivedAt = DateTimeOffset.UtcNow,
        });

        try
        {
            await db.SaveChangesAsync(ct);
            return true;
        }
        catch (DbUpdateException)
        {
            // Already recorded by an earlier (or concurrent) delivery — drop this duplicate.
            db.ChangeTracker.Clear();
            return false;
        }
    }

    public async Task<IReadOnlyList<RecordedNotification>> AllAsync(CancellationToken ct = default)
        => await db.ProcessedNotifications
            .OrderBy(r => r.ReceivedAt)
            .Select(r => new RecordedNotification(r.Key, r.Actie, r.ZaakId, r.Resource))
            .ToListAsync(ct);
}