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);
  }
}