using Events.FilesAPI.Infrastructure.Files;
using Events.FilesAPI.Features.RegistrationsExcel.Synchronize;
using Events.WebAPI.Handlers.EF.Data.Postgres;
using Microsoft.EntityFrameworkCore;
using MediatR;

namespace Events.FilesAPI.Features.RegistrationsExcel.Download;

public sealed class DownloadRegistrationsExcelHandler(
  EventsContext context,
  RegistrationsExcelFileGenerator generator,
  RegistrationsExcelFileLocator fileLocator) : IRequestHandler<DownloadRegistrationsExcelQuery, DownloadRegistrationsExcelResult>
{
  public async Task<DownloadRegistrationsExcelResult> Handle(DownloadRegistrationsExcelQuery request, CancellationToken cancellationToken)
  {
    bool exists = await context.Events
      .AsNoTracking()
      .AnyAsync(e => e.Id == request.EventId, cancellationToken);

    if (!exists)
      return new DownloadRegistrationsExcelResult(false, null);

    GeneratedFileReference? file = fileLocator.TryGet(request.EventId);

    if (file == null)
    {
      await generator.GenerateAsync(request.EventId, cancellationToken);
      file = fileLocator.TryGet(request.EventId);
    }

    return new DownloadRegistrationsExcelResult(true, file);
  }
}