using System.IO;
using System.Text;
using System.Security.Cryptography;
using System;
using SimpleValidator.Extensions;

namespace Tango.Core.Cryptography
{
    /// <summary>
    /// Represents an Rfc2898 <see cref="ICryptographer">Cryptographer</see>.
    /// </summary>
    /// <seealso cref="Tango.Core.Cryptography.ICryptographer" />
    public class Rfc2898Cryptographer : ICryptographer
    {
        /// <summary>
        /// Decrypts the specified text.
        /// </summary>
        /// <param name="text">The text.</param>
        /// <returns></returns>
        public string Decrypt(string text)
        {
            return Decrypt(text, Properties.Resources.EncryptionPassword);
        }

        /// <summary>
        /// Decrypts the specified text using the specified pass key.
        /// </summary>
        /// <param name="text">The text.</param>
        /// <param name="key">The key.</param>
        /// <returns></returns>
        public string Decrypt(string text, string key)
        {
            if (text.IsNullOrWhiteSpace()) return text;

            string EncryptionKey = key;
            text = text.Replace(" ", "+");
            byte[] cipherBytes = Convert.FromBase64String(text);
            using (Aes encryptor = Aes.Create())
            {
                Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
                encryptor.Key = pdb.GetBytes(32);
                encryptor.IV = pdb.GetBytes(16);
                using (MemoryStream ms = new MemoryStream())
                {
                    using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateDecryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(cipherBytes, 0, cipherBytes.Length);
                        cs.Close();
                    }
                    text = Encoding.Unicode.GetString(ms.ToArray());
                }
            }
            return text;
        }

        /// <summary>
        /// Encrypts the specified text.
        /// </summary>
        /// <param name="text">The text.</param>
        /// <returns></returns>
        public string Encrypt(string text)
        {
            return Encrypt(text, Properties.Resources.EncryptionPassword);
        }

        /// <summary>
        /// Encrypts the specified text using the specified pass key.
        /// </summary>
        /// <param name="text">The text.</param>
        /// <param name="key">The key.</param>
        /// <returns></returns>
        public string Encrypt(string text, string key)
        {
            if (text.IsNullOrWhiteSpace()) return text;

            string EncryptionKey = key;
            byte[] clearBytes = Encoding.Unicode.GetBytes(text);
            using (Aes encryptor = Aes.Create())
            {
                Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
                encryptor.Key = pdb.GetBytes(32);
                encryptor.IV = pdb.GetBytes(16);
                using (MemoryStream ms = new MemoryStream())
                {
                    using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateEncryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(clearBytes, 0, clearBytes.Length);
                        cs.Close();
                    }
                    text = Convert.ToBase64String(ms.ToArray());
                }
            }
            return text;
        }
    }
}