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

namespace Common.Helper
{
    public static class Crypto
    {
        private static string saltValue = "K0r3@GM3";
        private static string hashAlgorithm = "SHA1";
        private static int passwordIterations = 5;
        private static string initVector = "P@s$w0rDGm3KoR3@";
        private static int keySize = 256;
        private static int keySize128 = 128;

        /// <summary>
        /// Encrypts specified plaintext using Rijndael symmetric key algorithm and returns a
        /// base64-encoded result.
        /// </summary>
        /// <param name="plainText">Plain Text to Encrypt</param>
        /// <param name="passPhrase">Pass Phrase to use in Password Generation</param>
        /// <returns>Encrypted text encoded into Base 64 text format</returns>
        public static string Encrypt(string plainText, string passPhrase)
        {
            // Convert strings into byte arrays. Let us assume that strings only contain ASCII
            // codes. If strings include Unicode characters, use Unicode, UTF7, or UTF8 encoding.
            byte[] initVectorBytes = Encoding.ASCII.GetBytes(initVector);
            byte[] saltValueBytes = Encoding.ASCII.GetBytes(saltValue);

            // Convert our plaintext into a byte array. Let us assume that plaintext contains
            // UTF8-encoded characters.
            byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);

            // First, we must create a password, from which the key will be derived. This password
            // will be generated from the specified passphrase and salt value. The password will be
            // created using the specified hash algorithm. Password creation can be done in several iterations.
            var password = new PasswordDeriveBytes(
                passPhrase,
                saltValueBytes,
                hashAlgorithm,
                passwordIterations);

            // Use the password to generate pseudo-random bytes for the encryption key. Specify the
            // size of the key in bytes (instead of bits).
#pragma warning disable 618, 612
            byte[] keyBytes = password.GetBytes(keySize / 8);
#pragma warning restore 618, 612

            // Create uninitialized Rijndael encryption object.
            var symmetricKey = new RijndaelManaged();

            // It is reasonable to set encryption mode to Cipher Block Chaining (CBC). Use default
            // options for other symmetric key parameters.
            symmetricKey.Mode = CipherMode.CBC;

            // Generate encryptor from the existing key bytes and initialization vector. Key size
            // will be defined based on the number of the key bytes.
            ICryptoTransform encryptor = symmetricKey.CreateEncryptor(
                keyBytes,
                initVectorBytes);

            var memoryStream = new MemoryStream();

            // Define memory stream which will be used to hold encrypted data.
            var cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write);

            // Start encrypting.
            cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);

            // Finish encrypting.
            cryptoStream.FlushFinalBlock();

            // Convert our encrypted data from a memory stream into a byte array.
            byte[] cipherTextBytes = memoryStream.ToArray();

            // Close both streams.
            memoryStream.Close();
            cryptoStream.Close();

            // Convert encrypted data into a base64-encoded string.
            string cipherText = Convert.ToBase64String(cipherTextBytes);

            // Return encrypted string.
            return cipherText;
        }

        /// <summary>
        /// Decrypts specified cipherText using Rijndael symmetric key algorithm and returns a plain
        /// text result.
        /// </summary>
        /// <param name="cipherText">Encryted Text</param>
        /// <param name="passPhrase">Pass Phrase used in Password Generation</param>
        /// <returns></returns>
        public static string Decrypt(string cipherText, string passPhrase)
        {
            // Convert strings defining encryption key characteristics into byte arrays. Let us
            // assume that strings only contain ASCII codes. If strings include Unicode characters,
            // use Unicode, UTF7, or UTF8 encoding.
            byte[] initVectorBytes = Encoding.ASCII.GetBytes(initVector);
            byte[] saltValueBytes = Encoding.ASCII.GetBytes(saltValue);

            // Convert our ciphertext into a byte array.
            byte[] cipherTextBytes = Convert.FromBase64String(cipherText);

            // First, we must create a password, from which the key will be derived. This password
            // will be generated from the specified passphrase and salt value. The password will be
            // created using the specified hash algorithm. Password creation can be done in several iterations.
            var password = new PasswordDeriveBytes(
                passPhrase,
                saltValueBytes,
                hashAlgorithm,
                passwordIterations);

            // Use the password to generate pseudo-random bytes for the encryption key. Specify the
            // size of the key in bytes (instead of bits).
#pragma warning disable 618, 612
            byte[] keyBytes = password.GetBytes(keySize / 8);
#pragma warning restore 618, 612

            // Create uninitialized Rijndael encryption object.
            var symmetricKey = new RijndaelManaged();

            // It is reasonable to set encryption mode to Cipher Block Chaining (CBC). Use default
            // options for other symmetric key parameters.
            symmetricKey.Mode = CipherMode.CBC;

            // Generate decryptor from the existing key bytes and initialization vector. Key size
            // will be defined based on the number of the key bytes.
            ICryptoTransform decryptor = symmetricKey.CreateDecryptor(
                keyBytes,
                initVectorBytes);

            // Define memory stream which will be used to hold encrypted data.
            var memoryStream = new MemoryStream(cipherTextBytes);

            // Define cryptographic stream (always use Read mode for encryption).
            var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);

            // Since at this point we don't know what the size of decrypted data will be, allocate
            // the buffer long enough to hold ciphertext; plaintext is never longer than ciphertext.
            var plainTextBytes = new byte[cipherTextBytes.Length];

            // Start decrypting.
            int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);

            // Close both streams.
            memoryStream.Close();
            cryptoStream.Close();

            // Convert decrypted data into a string. Let us assume that the original plaintext
            // string was UTF8-encoded.
            string plainText = Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);

            // Return decrypted string.
            return plainText;
        }

        public static string Encrypt128(string plainText, string key)
        {
            RijndaelManaged RijndaelCipher = new RijndaelManaged();
            RijndaelCipher.Mode = CipherMode.ECB;
            RijndaelCipher.Padding = PaddingMode.None;
            RijndaelCipher.KeySize = keySize128;
            int paddingLengh = 16 - plainText.Length % 16;

            byte[] encrypByte = new byte[plainText.Length + paddingLengh];
            byte[] plainByte = Encoding.UTF8.GetBytes(plainText);

            for (int i = 0; i < encrypByte.Length; ++i)
            {
                if (i < plainByte.Length)
                {
                    encrypByte[i] = plainByte[i];
                }
                else
                {
                    encrypByte[i] = (byte)0x20;
                }
            }

            byte[] keyByte = Encoding.UTF8.GetBytes(key);

            ICryptoTransform Encryptor = RijndaelCipher.CreateEncryptor(keyByte, null);

            MemoryStream memoryStream = new MemoryStream();
            CryptoStream cryptoStream = new CryptoStream(memoryStream, Encryptor, CryptoStreamMode.Write);

            cryptoStream.Write(encrypByte, 0, encrypByte.Length);

            cryptoStream.FlushFinalBlock();

            byte[] cipherBytes = memoryStream.ToArray();

            memoryStream.Close();
            cryptoStream.Close();

            var encryptedData = BitConverter.ToString(cipherBytes).Replace("-", string.Empty);
            return encryptedData;
        }

        //public static string Decrypt128(string cipherText, string key)
        //{
        //    RijndaelManaged rijndaelManaged = new RijndaelManaged();
        //    // Convert our ciphertext into a byte array.
        //    byte[] cipherTextBytes = Convert.FromBase64String(cipherText);
        //    byte[] saltValueBytes = Encoding.ASCII.GetBytes(key);
        //    PasswordDeriveBytes SecretKey = new PasswordDeriveBytes(key, saltValueBytes);
        //    ICryptoTransform Decryptor = rijndaelManaged.CreateDecryptor(SecretKey.GetBytes(32), SecretKey.GetBytes(16));
        //    MemoryStream memoryStream = new MemoryStream(cipherTextBytes);
        //    CryptoStream cryptoStream = new CryptoStream(memoryStream, Decryptor, CryptoStreamMode.Read);
        //    byte[] plainText = new byte[cipherTextBytes.Length];

        // int DecryptedCount = cryptoStream.Read(plainText, 0, plainText.Length);

        // memoryStream.Close(); cryptoStream.Close();

        // string DecryptedData = Encoding.Unicode.GetString(plainText, 0, DecryptedCount);

        //    return DecryptedData;
        //}
        /* @Max - 2018.10.25
         * 지정한 개수만큼의 랜덤스트링을 만들어 리턴하는 함수
         * */

        public static string GetRandomString(int _totLen)
        {
            Random rand = new Random();
            string input = "abcdefghijklmnopqrstuvwxyz0123456789";
            var chars = Enumerable.Range(0, _totLen).Select(x => input[rand.Next(0, input.Length)]);
            return new string(chars.ToArray());
        }

        /* @Max - 2018.11.07
         * 지정한 개수만큼의 랜덤숫자를 만들어 리턴하는 함수
         * */

        public static string GetRandomNumber(int _totLen)
        {
            Random rand = new Random();
            string input = "0123456789";
            var chars = Enumerable.Range(0, _totLen).Select(x => input[rand.Next(0, input.Length)]);
            return new string(chars.ToArray());
        }
    }
}