using System;
using System.IO;
using System.Security.Cryptography;
using TINK.Model.Device;

namespace TINK.Services.BluetoothLock.Crypto
{
	public class Cipher : ICipher
	{
		/// <summary> Decrypt data. </summary>
		/// <remarks>
		/// Further info see:
		/// https://docs.microsoft.com/en-us/dotnet/api/system.security.cryptography.aes?view=netcore-3.1 for further info
		//  https://docs.microsoft.com/en-us/dotnet/standard/security/cryptographic-services
		//  https://stackoverflow.com/questions/24903575/how-to-return-byte-when-decrypt-using-cryptostream-descryptoserviceprovider/24903689

		/// </remarks>
		/// <param name="key">Key to decrypt data with.</param>
		/// <param name="encrypted">Encrpyted data to decrypt.</param>
		/// <returns>Decrypted data.</returns>
		public byte[] Decrypt(byte[] key, byte[] encrypted)
		{
			// Check arguments.
			if (encrypted == null || encrypted.Length <= 0)
				throw new ArgumentNullException(nameof(encrypted));

			if (key == null || key.Length <= 0)
				throw new ArgumentNullException(nameof(key));

			using (Aes aesAlg = Aes.Create())
			{
				aesAlg.KeySize = 192;
				aesAlg.Mode = CipherMode.ECB;
				aesAlg.Padding = PaddingMode.None;
				aesAlg.Key = key;

				// Create a decryptor to perform the stream transform.
				ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

				// Create the streams used for decryption.
				using (var msDecrypt = new MemoryStream())
				{
					using (var csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Write))
					{
						csDecrypt.Write(encrypted, 0, encrypted.Length);
						csDecrypt.FlushFinalBlock();
						return msDecrypt.ToArray();
					}
				}
			}
		}

		public byte[] Encrypt(byte[] key, byte[] clear)
		{
			// Check arguments.
			if (clear == null || clear.Length <= 0)
				throw new ArgumentNullException("plainText");

			if (key == null || key.Length <= 0)
				throw new ArgumentNullException("Key");

			// Create an AesCryptoServiceProvider object
			// with the specified key and IV.
			using (AesCryptoServiceProvider aesAlg = new AesCryptoServiceProvider())
			{
				aesAlg.KeySize = 192;
				aesAlg.Mode = CipherMode.ECB;
				aesAlg.Padding = PaddingMode.None;
				aesAlg.Key = key;

				// Create an encryptor to perform the stream transform.
				ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

				// Create the streams used for encryption.
				using (var msEncrypt = new MemoryStream())
				{
					using (var csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
					{
						csEncrypt.Write(clear, 0, clear.Length);
						csEncrypt.FlushFinalBlock();
						return msEncrypt.ToArray();
					}
				}
			}

		}
	}
}