using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

namespace DTS.Common.Security
{
    public static class Encryption
    {
        /// <summary>
        /// 
        /// </summary>
        /// <param name="plainText"></param>
        /// <param name="key"></param>
        /// <param name="iv"></param>
        /// <returns></returns>
        public static byte[] EncryptStringToBytes(string plainText, byte[] key, byte[] iv)
        {

            // Check arguments. 
            if (plainText == null || plainText.Length <= 0) throw new ArgumentNullException(nameof(plainText));
            if (key == null || key.Length <= 0) throw new ArgumentNullException(nameof(key));
            if (iv == null || iv.Length <= 0) throw new ArgumentNullException(nameof(key));
            byte[] encrypted;
            // Create an RijndaelManaged object 
            // with the specified key and IV. 

            using (var rijAlg = new AesCryptoServiceProvider())
            {
                rijAlg.Key = key;
                rijAlg.IV = iv;

                // Create a decrytor to perform the stream transform.
                var encryptor = rijAlg.CreateEncryptor(rijAlg.Key, rijAlg.IV);

                // Create the streams used for encryption. 
                using (var msEncrypt = new MemoryStream())
                {
                    using (var csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                    {
                        using (var swEncrypt = new StreamWriter(csEncrypt))
                        {

                            //Write all data to the stream.
                            swEncrypt.Write(plainText);
                        }
                        encrypted = msEncrypt.ToArray();
                    }
                }
            }


            // Return the encrypted bytes from the memory stream. 
            return encrypted;
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="cipherText"></param>
        /// <param name="key"></param>
        /// <param name="iv"></param>
        /// <returns></returns>
        public static string DecryptStringFromBytes(byte[] cipherText, byte[] key, byte[] iv)
        {
            // Check arguments. 
            if (cipherText == null || cipherText.Length <= 0) throw new ArgumentNullException(nameof(cipherText));
            if (key == null || key.Length <= 0) throw new ArgumentNullException(nameof(key));
            if (iv == null || iv.Length <= 0) throw new ArgumentNullException(nameof(key));

            // Declare the string used to hold 
            // the decrypted text. 
            string plaintext = null;

            // Create an RijndaelManaged object 
            // with the specified key and IV. 
            using (var rijAlg = new AesCryptoServiceProvider())
            {
                rijAlg.Key = key;
                rijAlg.IV = iv;

                // Create a decrytor to perform the stream transform.
                var decryptor = rijAlg.CreateDecryptor(rijAlg.Key, rijAlg.IV);

                // Create the streams used for decryption. 
                using (var msDecrypt = new MemoryStream(cipherText))
                {
                    using (var csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                    {
                        using (var srDecrypt = new StreamReader(csDecrypt))
                        {

                            // Read the decrypted bytes from the decrypting stream 
                            // and place them in a string.
                            plaintext = srDecrypt.ReadToEnd();
                        }
                    }
                }
            }

            return plaintext;
        }

    }
}