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

namespace DealerSelection.Api.CommonUtil
{

    public static class AESEncryption
    {

        public static byte[] EncryptString(string plainText, byte[] key, byte[] iv)
        {
            // Instantiate a new Aes object to perform string symmetric encryption
            Aes encryptor = Aes.Create();

            encryptor.Mode = CipherMode.CBC;

            // Set key and IV
            byte[] aesKey = new byte[32];
            Array.Copy(key, 0, aesKey, 0, 32);
            encryptor.Key = aesKey;
            encryptor.IV = iv;

            // Instantiate a new MemoryStream object to contain the encrypted bytes
            MemoryStream memoryStream = new MemoryStream();

            // Instantiate a new encryptor from our Aes object
            ICryptoTransform aesEncryptor = encryptor.CreateEncryptor();

            // Instantiate a new CryptoStream object to process the data and write it to the 
            // memory stream
            CryptoStream cryptoStream = new CryptoStream(memoryStream, aesEncryptor, CryptoStreamMode.Write);

            // Convert the plainText string into a byte array
            byte[] plainBytes = Encoding.ASCII.GetBytes(plainText);

            // Encrypt the input plaintext string
            cryptoStream.Write(plainBytes, 0, plainBytes.Length);

            // Complete the encryption process
            cryptoStream.FlushFinalBlock();

            // Convert the encrypted data from a MemoryStream to a byte array
            byte[] cipherBytes = memoryStream.ToArray();

            // Close both the MemoryStream and the CryptoStream
            memoryStream.Close();
            cryptoStream.Close();

            // Convert the encrypted byte array to a base64 encoded string
            string cipherText = Convert.ToBase64String(cipherBytes, 0, cipherBytes.Length);

            // Return the encrypted data as a string
            return cipherBytes;
        }

        public static string DecryptString(string cipherText, string key)
        {
            // Instantiate a new Aes object to perform string symmetric encryption
            Aes encryptor = Aes.Create();

            encryptor.Mode = CipherMode.CBC;

            byte[] salt = Convert.FromBase64String(cipherText).Take(16).ToArray();
            byte[] IVV = Convert.FromBase64String(cipherText).Skip(16).Take(16).ToArray();


            byte[] aesKey;
            using (var pbkdf2 = new Rfc2898DeriveBytes(key, salt, 65536, HashAlgorithmName.SHA256))
            {
                aesKey = pbkdf2.GetBytes(32);
            }

            // Set key and IV
            //byte[] aesKey = new byte[32];
            //Array.Copy(key, 0, aesKey, 0, 32);
            encryptor.Key = aesKey;
            encryptor.IV = IVV;




            // Instantiate a new MemoryStream object to contain the encrypted bytes
            MemoryStream memoryStream = new MemoryStream();

            // Instantiate a new encryptor from our Aes object
            ICryptoTransform aesDecryptor = encryptor.CreateDecryptor();

            // Instantiate a new CryptoStream object to process the data and write it to the 
            // memory stream
            CryptoStream cryptoStream = new CryptoStream(memoryStream, aesDecryptor, CryptoStreamMode.Write);

            // Will contain decrypted plaintext
            string plainText = string.Empty;

            try
            {
                // Convert the ciphertext string into a byte array
                byte[] cipherBytes = Convert.FromBase64String(cipherText).Skip(32).ToArray();

                // Decrypt the input ciphertext string
                cryptoStream.Write(cipherBytes, 0, cipherBytes.Length);

                // Complete the decryption process
                cryptoStream.FlushFinalBlock();

                // Convert the decrypted data from a MemoryStream to a byte array
                byte[] plainBytes = memoryStream.ToArray();

                // Convert the decrypted byte array to string
                plainText = Encoding.ASCII.GetString(plainBytes, 0, plainBytes.Length);
            }
            finally
            {
                // Close both the MemoryStream and the CryptoStream
                memoryStream.Close();
                cryptoStream.Close();
            }

            // Return the decrypted data as a string
            return plainText;
        }

        public static dynamic ReturnEncKey(string password,string message)
        {

            byte[] salt = new byte[16];
            byte[] encKey;
            using (var rng = RandomNumberGenerator.Create())
            {
                rng.GetBytes(salt);
            }

            using (var pbkdf2 = new Rfc2898DeriveBytes(password, salt, 65536, HashAlgorithmName.SHA256))
            {
                encKey = pbkdf2.GetBytes(32);
            }

            Random random = new Random();

            byte[] iv = new byte[16];
            random.NextBytes(iv);
            byte[] encrypted = EncryptString(message, encKey, iv);
            byte[] finalstring = salt.Concat(iv).Concat(encrypted).ToArray();
            string encstring = Convert.ToBase64String(finalstring);

            return encstring;
        }

    }

}