namespace MyNamespace
{
    public class Request
    {
        public int EntityId { get; set; }

        public DateTime EventDateTime { get; set; }

        public EventType EventType { get; set; }

        public string ProcedureNumber { get; set; }

        public string Inn { get; set; }

        public string Kpp { get; set; }
    }

    public interface IMessageBuilder
    {
        IEnumerable<EventType> EventTypes { get; }

        EtpEventBusMessage Build(object request);
    }

    public interface IMessageBuilder<in T> : IMessageBuilder where T : Request
    {
        EtpEventBusMessage BuildTyped(T request);
    }

    public abstract class MessageBuilder<T> : IMessageBuilder<T> where T : Request
    {
        protected EtpEventBusMessage Message { get; } = new EtpEventBusMessage();

        public IEnumerable<EventType> EventTypes { get; }

        protected MessageBuilder()
        {
            if (typeof(T).GetCustomAttributes(typeof(EventTypeAttribute), true) is EventTypeAttribute[] attributes && attributes.IsNotEmpty())
            {
                EventTypes = attributes
                    .Select(x => x.EventType)
                    .ToArray();
            }
        }

        public EtpEventBusMessage Build(object request)
        {
            return BuildTyped((T) request);
        }

        public EtpEventBusMessage BuildTyped(T request)
        {
            Message.EntityId = request.EntityId;
            Message.EventDateTime = request.EventDateTime;
            Message.EventType = request.EventType;
            Message.Inn = "BBB";

            return Create(request);
        }

        protected abstract EtpEventBusMessage Create(T request);
    }

    public interface ISender
    {
        Task SendAsync<TRequest>(TRequest request, CancellationToken cancellation = default) where TRequest : Request;
    }

    public sealed class Sender : ISender
    {
        private readonly IEnumerable<IMessageBuilder> _builders;

        private readonly IMessageQueueClient _client;

        public Sender(IEnumerable<IMessageBuilder> builders, IMessageQueueClient client)
        {
            _builders = builders;
            _client = client;
        }

        public async Task SendAsync<TRequest>(TRequest request, CancellationToken cancellation = default) where TRequest : Request
        {
            var type = request.EventType; // тут его может не быть, нужно брать из атрибутов

            var builder = _builders.FirstOrDefault(x => x.EventTypes.Contains(type)) ?? throw new Exception("Not Found");

            var message = builder.Build(request);

            await _client.PublishAsync(message, cancellation);
        }
    }

    [EventType(EventType.CustomerAuthenticatedByCert)]
    [EventType(EventType.CustomerAuthenticatedByCert)]
    [EventType(EventType.CustomerAuthenticatedByCert)]
    [EventType(EventType.CustomerAuthenticatedByCert)]
    public sealed class CustomRequest : Request
    {
        public string NotificationText { get; set; }

        public PurchaseMethodType PyMethodType { get; set; }
    }

    public sealed class MyCustomMessageBuilder : MessageBuilder<CustomRequest>
    {
        protected override EtpEventBusMessage Create(CustomRequest request)
        {
            Message.EventDateTime = DateTime.UtcNow;

            Message.EventType = request.PyMethodType == PurchaseMethodType.Auction
                ? EventType.CustomerAuthenticatedByCert
                : EventType.AccreditationRequestResultSendNotificationByOperatorForCustomer;

            Message.EventAttributes.Add(EtpEventAttributeType.NotificationText, request.NotificationText);

            return Message;
        }
    }

    public sealed class Client
    {
        public void Do()
        {
            ISender sender = new Sender(new List<IMessageBuilder>(), null);

            var request = new Request
            {
                EntityId = 1,
                //EventDateTime = DateTime.UtcNow,
                //NotificationText = nameof(CustomRequest.NotificationText),
            };

            sender
                .SendAsync(request, CancellationToken.None)
                .GetAwaiter()
                .GetResult();
        }
    }
}