online_security_project/lib/Request.cs

namespace lib;

public enum RequestType {
    Register = 1,
    ConfirmRegister = 2,
    Login = 3,
    GetMessages = 4,
    GetUserKey = 5,
    SendMessage = 6,
}

public static class Request {
    public static byte[] CreateRequest(RequestType Type, ref byte counter, byte[] data) {
        if(data.Length > 13) {
            throw new Exception("extra data is too long");
        }

        byte[] msg = new byte[128];
        msg[0] = 0; // version
        msg[1] = (byte)Type;
        msg[2] = counter;
        if(counter == byte.MaxValue) {
            counter = 0;
        }
        else {
            counter += 1;
        }

        // insert data 3..16
        Array.Copy(data, 0, msg, 3, data.Length);
        return msg;
    }
}