using System;
using System.Collections.Generic;
using System.Security.Cryptography;
using System.Text;
using lib;

namespace client;

public class Message
{
    public uint Id { set; get; }
    public string Sender { set; get; }
    public bool IsAck { set; get; }
    public string Content { set; get; }
    public byte[] Signature { set; get; }

    public Message(byte[] bytes)
    {
        if (bytes[0] != 0)
        {
            Console.WriteLine("Failed parsing message, unsupported version");
        }
        // skip the first byte for simplicity
        bytes = bytes[1..];
        Id = BitConverter.ToUInt32(bytes, 0);
        Sender = Utils.BytesToNumber(bytes[4..12]);
        IsAck = bytes[12] != 0;
        Content = Encoding.UTF8.GetString(bytes[13..bytes.Length]);
        Signature = [];
    }

    public Message(uint Id, string Sender, bool IsAck, string Content)
    {
        this.Id = Id;
        this.Sender = Sender;
        this.IsAck = IsAck;
        this.Content = Content;
        Signature = [];
    }

    public void CalculateSignature(RSA key)
    {
        Signature = key.SignData(Bytes(), HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
    }

    public bool IsSignatureValid(RSA key)
    {
        return key.VerifyData(Bytes(), Signature, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
    }

    public byte[] Bytes()
    {
        List<byte> msg = [];
        // 0..4
        msg.AddRange(BitConverter.GetBytes(Id));
        // 4..12
        msg.AddRange(Utils.NumberToBytes(Sender));
        // 12
        msg.Add((byte)(IsAck ? 1 : 0));
        // 13..(len - 32)
        msg.AddRange(Encoding.UTF8.GetBytes(Content));

        return [0, .. msg];
    }
}