using System.Security.Cryptography;
using Microsoft.Extensions.Logging;

namespace Server;

public class AesProvider
{
	private readonly Aes _aes;
	private readonly ICryptoTransform _encryptor;
	private readonly ICryptoTransform _decryptor;
	private readonly ILogger _logger;

	public AesProvider(ILoggerFactory loggerFactory, Span<byte> key, Span<byte> iv)
	{
		_logger = loggerFactory.CreateLogger(nameof(AesProvider));
		_aes = Aes.Create();
		_aes.Key = key.ToArray();
		_aes.IV = iv.ToArray();
		_encryptor = _aes.CreateEncryptor();
		_decryptor = _aes.CreateDecryptor();
	}

	public Span<byte> Encrypt(Span<byte> input)
	{
		using MemoryStream memoryStream = new MemoryStream();
		using CryptoStream cryptoStream = new CryptoStream(memoryStream, _encryptor, CryptoStreamMode.Write);
		cryptoStream.Write(input);
		cryptoStream.Flush();

		Span<byte> bytes = memoryStream.ToArray();

		return bytes;
	}

	public Span<byte> Decrypt(Span<byte> input)
	{
		using MemoryStream memoryStream = new MemoryStream(input.ToArray());
		using CryptoStream cryptoStream = new CryptoStream(memoryStream, _decryptor, CryptoStreamMode.Read);
		Span<byte> bytes = new byte[input.Length];
		var i = cryptoStream.Read(bytes);
		if (i > 0)
			_logger.LogWarning("CryptoStream hasn't been read till the end. ({length}", i);

		return bytes;
	}
}