WebApi + ClientApp, GraphQL, Reflection

Events-WebApi/Events.FilesAPI/Features/Certificates/Download/DownloadCertificateHandler.cs

@@ -0,0 +1,35 @@
+using Events.FilesAPI.Infrastructure.Files;
+using Events.FilesAPI.Features.Certificates.Synchronize;
+using Events.WebAPI.Handlers.EF.Data.Postgres;
+using MediatR;
+using Microsoft.EntityFrameworkCore;
+
+namespace Events.FilesAPI.Features.Certificates.Download;
+
+public sealed class DownloadCertificateHandler(
+  EventsContext context,
+  CertificateFileGenerator generator,
+  CertificateFileLocator fileLocator) : IRequestHandler<DownloadCertificateQuery, DownloadCertificateResult>
+{
+  public async Task<DownloadCertificateResult> Handle(DownloadCertificateQuery request, CancellationToken cancellationToken)
+  {
+    var registration = await context.Registrations
+      .AsNoTracking()
+      .Where(r => r.Id == request.RegistrationId)
+      .Select(r => new { r.EventId, r.PersonId })
+      .SingleOrDefaultAsync(cancellationToken);
+
+    if (registration == null)
+      return new DownloadCertificateResult(false, null);
+
+    GeneratedFileReference? file = fileLocator.TryGet(registration.EventId, registration.PersonId);
+
+    if (file == null)
+    {
+      await generator.GenerateAsync(registration.EventId, registration.PersonId, cancellationToken);
+      file = fileLocator.TryGet(registration.EventId, registration.PersonId);
+    }
+
+    return new DownloadCertificateResult(true, file);
+  }
+}