ProtobufStreamMessageSerializer.cs

using ProtoBuf;
using System.Text;

namespace SmartIOT.Connector.Messages.Serializers;

public class ProtobufStreamMessageSerializer : IStreamMessageSerializer
{
    public object? DeserializeMessage(Stream stream)
    {
        try
        {
            byte typeValue;
            using (BinaryReader reader = new BinaryReader(stream, Encoding.UTF8, true))
            {
                typeValue = reader.ReadByte();
            }

            return typeValue switch
            {
                1 => DeserializeMessage<TagEvent>(stream),
                2 => DeserializeMessage<DeviceEvent>(stream),
                3 => DeserializeMessage<TagWriteRequestCommand>(stream),
                99 => DeserializeMessage<PingMessage>(stream),
                _ => throw new InvalidDataException($"Message type {typeValue} is not recognized"),
            };
        }
        catch (EndOfStreamException)
        {
            return null;
        }
    }

    private T DeserializeMessage<T>(Stream stream)
    {
        return Serializer.DeserializeWithLengthPrefix<T>(stream, PrefixStyle.Base128);
    }

    public void SerializeMessage(Stream stream, object message)
    {
        switch (message)
        {
            case TagEvent t:
                SerializeMessage(1, stream, t);
                break;

            case DeviceEvent d:
                SerializeMessage(2, stream, d);
                break;

            case TagWriteRequestCommand c:
                SerializeMessage(3, stream, c);
                break;

            case PingMessage p:
                SerializeMessage(99, stream, p);
                break;

            default:
                throw new ArgumentException($"Message type {message.GetType().FullName} is not managed", nameof(message));
        }
    }

    private void SerializeMessage<T>(byte typeValue, Stream stream, T message)
    {
        // serialize the type
        stream.WriteByte(typeValue);

        // serialize length + payload
        Serializer.SerializeWithLengthPrefix<T>(stream, message, PrefixStyle.Base128);
    }
}