using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

namespace ChatApi.Services.Crypt
{
    public class CryptUtil
    {
        private readonly IConfigurationManager _configuration;

        public CryptUtil(IConfigurationManager configuration)
        {
            _configuration = configuration;
        }
        public string Encrypt(string text)
        {
            string key = _configuration.GetSection("DataKey").Value;
            using (Aes aes = Aes.Create())
            {
                aes.Key = Encoding.UTF8.GetBytes(key.PadRight(32).Substring(0, 32));
                aes.GenerateIV(); // Cria um vetor de inicialização aleatório
                byte[] iv = aes.IV;

                using (var encryptor = aes.CreateEncryptor(aes.Key, iv))
                using (var ms = new MemoryStream())
                {
                    // Primeiro, escreva o IV para o fluxo (será necessário para descriptografia)
                    ms.Write(iv, 0, iv.Length);

                    using (var cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
                    using (var writer = new StreamWriter(cs))
                    {
                        writer.Write(text);
                    }

                    return Convert.ToBase64String(ms.ToArray());
                }
            }
        }

        public string Descrypt(string text)
        {
            string key = _configuration.GetSection("DataKey").Value;
            byte[] bytes = Convert.FromBase64String(text);

            using (Aes aes = Aes.Create())
            {
                aes.Key = Encoding.UTF8.GetBytes(key.PadRight(32).Substring(0, 32));

                // Extrair o IV do início dos dados criptografados
                byte[] iv = new byte[aes.BlockSize / 8];
                Array.Copy(bytes, 0, iv, 0, iv.Length);
                aes.IV = iv;

                using (var decryptor = aes.CreateDecryptor(aes.Key, aes.IV))
                using (var ms = new MemoryStream(bytes, iv.Length, bytes.Length - iv.Length))
                using (var cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Read))
                using (var reader = new StreamReader(cs))
                {
                    return reader.ReadToEnd();
                }
            }
        }
    }
}