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

namespace PrevuAPIUtils
{
    public class EncryptionUtility
    {
        static readonly string PasswordHash = "6ACFFE9475614D989873CB421FDD6F55";
        static readonly string SaltKey = "79B34E198448417F98F665518598635F";
        static readonly string VIKey = "EEDB0E14F82C44DB";
        public static string CreateToken(string clientName,DateTime ContractEndDate, string Environment)
        {

            string data = clientName + ContractEndDate.ToString("MM/dd/yyyy") + Environment;
            return Encrypt(data);
        }
        public static string Encrypt(string data)
        {
            byte[] dataBytes = Encoding.UTF8.GetBytes(data);
            byte[] keyBytes = new Rfc2898DeriveBytes(PasswordHash, Encoding.ASCII.GetBytes(SaltKey)).GetBytes(256 / 8);
            AesCryptoServiceProvider aes = new AesCryptoServiceProvider();
            var encryptor = aes.CreateEncryptor(keyBytes, Encoding.ASCII.GetBytes(VIKey));
            // var symmetricKey = new RijndaelManaged() { Mode = CipherMode.CBC,  Padding = PaddingMode.PKCS7};
            //var encryptor = symmetricKey.CreateEncryptor(keyBytes, Encoding.ASCII.GetBytes(VIKey));
            byte[] cipherTextBytes;
            using (var memoryStream = new MemoryStream())
            {
                using (var cryptoStream = new CryptoStream(memoryStream, encryptor, CryptoStreamMode.Write))
                {
                    cryptoStream.Write(dataBytes, 0, dataBytes.Length);
                    cryptoStream.FlushFinalBlock();
                    cipherTextBytes = memoryStream.ToArray();
                    cryptoStream.Close();
                }
                memoryStream.Close();
            }
            return Convert.ToBase64String(cipherTextBytes).Replace('+','-').Replace('/','_');
        }
        public static string parseToken(string token)
        {
            return Decrypt(token);
        }
        public static string Decrypt(string token)
        {
            byte[] cipherTextBytes = Convert.FromBase64String(token.Replace('-', '+').Replace('_', '/'));
            byte[] keyBytes = new Rfc2898DeriveBytes(PasswordHash, Encoding.ASCII.GetBytes(SaltKey)).GetBytes(256 / 8);
            AesCryptoServiceProvider aes = new AesCryptoServiceProvider();
            var decryptor = aes.CreateDecryptor(keyBytes, Encoding.ASCII.GetBytes(VIKey));
            //var symmetricKey = new RijndaelManaged() { Mode = CipherMode.CBC, Padding = PaddingMode.PKCS7 };

            //var decryptor = symmetricKey.CreateDecryptor(keyBytes, Encoding.ASCII.GetBytes(VIKey));
            var memoryStream = new MemoryStream(cipherTextBytes);
            var cryptoStream = new CryptoStream(memoryStream, decryptor, CryptoStreamMode.Read);
            byte[] plainTextBytes = new byte[cipherTextBytes.Length];

            int decryptedByteCount = cryptoStream.Read(plainTextBytes, 0, plainTextBytes.Length);
            memoryStream.Close();
            cryptoStream.Close();
            return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount).TrimEnd("\0".ToCharArray());
        }
    }
}