hrynco-notification-service/HrynCo.NotificationService.Services/TemplateDefinitions/DeleteUnusedServiceLanguageHandler.cs

using HrynCo.NotificationService.DAL.Abstract.Repositories;
using HrynCo.NotificationService.DAL.Abstract.Templates;
using HrynCo.NotificationService.Services.Core;
using HrynCo.NotificationService.Services.Logging;
using static HrynCo.NotificationService.Services.Core.ServiceResultHelper;

namespace HrynCo.NotificationService.Services.TemplateDefinitions;

internal sealed class DeleteUnusedServiceLanguageHandler(
    IContextualSerilogLogger<DeleteUnusedServiceLanguageCommand> logger, INotificationServiceRepository services)
    : RequestHandler<DeleteUnusedServiceLanguageCommand, ServiceResult<Unit>>(logger)
{
    protected override async Task<ServiceResult<Unit>> DoOnHandle(DeleteUnusedServiceLanguageCommand request, CancellationToken cancellationToken)
    {
        if (request.Revision == Guid.Empty)
            return Failure<Unit>("A nonempty service revision is required.", ServiceErrorCode.InvalidRequest);
        var service = await services.GetAsync(request.ServiceId, cancellationToken);
        var language = service?.Languages.SingleOrDefault(l => l.Id == request.LanguageId);
        if (language is null)
            return Failure<Unit>("Service language not found.", ServiceErrorCode.NotFound);
        if (language.VersionCount > 0)
            return Failure<Unit>("This language has template versions. Use delete-with-versions with explicit confirmation and the current count.", ServiceErrorCode.Conflict);
        try
        {
            // The repository repeats the zero-count and revision checks under its mutation lock.
            await services.RemoveLanguageAsync(request.ServiceId, request.LanguageId, 0, request.Revision, cancellationToken);
            return Success(Unit.Value);
        }
        catch (EmailTemplateWriteException error)
        {
            return Failure<Unit>(error.Message, error.IsConflict ? ServiceErrorCode.Conflict : ServiceErrorCode.InvalidRequest);
        }
    }
}