using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

}

​

internal class KeyGenerator

{

    internal string Key { get; private set; }

    internal string PublicPersonId { get; private set; }

​

    [System.Text.Json.Serialization.JsonConstructor]

    private KeyGenerator(string _key,string _publicPersonId)

    {

        Key = _key;

        PublicPersonId = _publicPersonId;

    }

    private KeyGenerator(string publicPersonId)

    {

        Key = $"EXT-{Guid.NewGuid():D}".ToUpper();

        PublicPersonId = publicPersonId;

    }

​

    internal static KeyGenerator New(string publicPersonId) => new(publicPersonId);

    internal string Encode()

    {

        var selfSerialized = System.Text.Json.JsonSerializer.Serialize(this);

        var _keyBytes = System.Text.Encoding.UTF8.GetBytes(selfSerialized);

        return Convert.ToBase64String(_keyBytes);

    }

​

    internal static KeyGenerator Decode(string externalKey)

    {

        try

        {

            var _keyBytes = Convert.FromBase64String(externalKey);

            using MemoryStream stream = new(_keyBytes);

            return System.Text.Json.JsonSerializer.Deserialize<KeyGenerator>(stream);

        }

        catch (Exception)

        {

            return null;

        }

    }

}