ExtraChat/client/ExtraChat/Formatters/RegisterResponseFormatter.cs

using System.Text;
using ExtraChat.Protocol;
using MessagePack;
using MessagePack.Formatters;

namespace ExtraChat.Formatters;

public class RegisterResponseFormatter : IMessagePackFormatter<RegisterResponse> {
    public void Serialize(ref MessagePackWriter writer, RegisterResponse value, MessagePackSerializerOptions options) {
        if (value is RegisterResponse.Failure) {
            writer.WriteString(Encoding.UTF8.GetBytes("failure"));
            return;
        }
        
        writer.WriteMapHeader(1);

        var key = value switch {
            RegisterResponse.Challenge => "challenge",
            RegisterResponse.Failure => "failure",
            RegisterResponse.Success => "success",
            _ => throw new ArgumentOutOfRangeException(nameof(value)),
        };

        writer.WriteString(Encoding.UTF8.GetBytes(key));

        switch (value) {
            case RegisterResponse.Challenge challenge: {
                writer.WriteArrayHeader(1);
                writer.WriteString(Encoding.UTF8.GetBytes(challenge.Text));
                break;
            }
            case RegisterResponse.Failure:
                break;
            case RegisterResponse.Success success: {
                writer.WriteArrayHeader(1);
                writer.WriteString(Encoding.UTF8.GetBytes(success.Key));
                break;
            }
        }
    }

    public RegisterResponse Deserialize(ref MessagePackReader reader, MessagePackSerializerOptions options) {
        if (reader.NextMessagePackType == MessagePackType.Map) {
            if (reader.ReadMapHeader() != 1) {
                throw new MessagePackSerializationException("Invalid map length");
            }
        } else if (reader.NextMessagePackType == MessagePackType.String) {
            if (reader.ReadString() != "failure") {
                throw new MessagePackSerializationException("Invalid RegisterResponse");
            }

            return new RegisterResponse.Failure();
        } else {
            throw new MessagePackSerializationException("Invalid RegisterResponse");
        }

        var key = reader.ReadString();
        switch (key) {
            case "challenge": {
                if (reader.ReadArrayHeader() != 1) {
                    throw new MessagePackSerializationException("Invalid RegisterResponse");
                }
                
                var text = reader.ReadString();
                return new RegisterResponse.Challenge(text);
            }
            case "failure":
                throw new MessagePackSerializationException("Invalid RegisterResponse");
            case "success": {
                if (reader.ReadArrayHeader() != 1) {
                    throw new MessagePackSerializationException("Invalid RegisterResponse");
                }
                
                var text = reader.ReadString();
                return new RegisterResponse.Success(text);
            }
            default:
                throw new MessagePackSerializationException("Invalid RegisterResponse type");
        }
    }
}