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();
                    }
                }
            }

        }
    }
}