using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Sifrator
{

    using System;
    using System.IO;
    using System.Security.Cryptography;

    public class AesCipher
    {
        public static byte[] AES_Encrypt(string output, byte[] bytesToBeEncrypted, byte[] passwordBytes)
        {
            byte[] encryptedBytes = null;

            byte[] saltBytes = new byte[] { 1, 2, 3, 4, 5, 6, 7, 8 };

            using (var memoryStream = new MemoryStream())
            {
                using (RijndaelManaged AES = new RijndaelManaged())
                {
                    AES.KeySize = 256;
                    AES.BlockSize = 128;

                    var key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
                    AES.Key = key.GetBytes(AES.KeySize / 8);
                    AES.IV = key.GetBytes(AES.BlockSize / 8);

                    AES.Mode = CipherMode.CBC;

                    using (var cs = new CryptoStream(memoryStream, AES.CreateEncryptor(), CryptoStreamMode.Write))
                    {
                        byte[] tmp = passwordBytes.Concat(bytesToBeEncrypted).ToArray();
                            //new byte[passwordBytes.Length + bytesToBeEncrypted.Length];
                        cs.Write(tmp, 0, tmp.Length);
                        cs.Close();
                    }

                    encryptedBytes = memoryStream.ToArray();
                }
            }

            return encryptedBytes;
        }

        public static byte[] AES_Decrypt(byte[] bytesToBeDecrypted, byte[] passwordBytes)
        {
            byte[] decryptedBytes = null;

            // Set your salt here, change it to meet your flavor:
            // The salt bytes must be at least 8 bytes.
            byte[] saltBytes = new byte[] { 1, 2, 3, 4, 5, 6, 7, 8 };

            using (MemoryStream ms = new MemoryStream())
            {
                using (RijndaelManaged AES = new RijndaelManaged())
                {
                    AES.KeySize = 256;
                    AES.BlockSize = 128;

                    var key = new Rfc2898DeriveBytes(passwordBytes, saltBytes, 1000);
                    AES.Key = key.GetBytes(AES.KeySize / 8);
                    AES.IV = key.GetBytes(AES.BlockSize / 8);

                    AES.Mode = CipherMode.CBC;

                    using (var cs = new CryptoStream(ms, AES.CreateDecryptor(), CryptoStreamMode.Write))
                    {
                        cs.Write(bytesToBeDecrypted, 0, bytesToBeDecrypted.Length);
                        cs.FlushFinalBlock();
                        cs.Close();
                    }
                    decryptedBytes = ms.ToArray();
                }
            }

            return decryptedBytes;
        }

        public static void EncryptFile(string filePath)
        {

            byte[] bytesToBeEncrypted = File.ReadAllBytes(filePath);

            Random rnd = new Random();
            byte[] passwordBytesENCR = new byte[2];//Encoding.UTF8.GetBytes(password);
            rnd.NextBytes(passwordBytesENCR);

            // Hash the password with SHA256
            passwordBytesENCR = SHA256.Create().ComputeHash(passwordBytesENCR);

            string fileEncrypted = "crypted_" + filePath.Split('\\')[filePath.Split('\\').Length - 1];
            byte[] bytesEncrypted = AES_Encrypt(fileEncrypted, bytesToBeEncrypted, passwordBytesENCR);

            File.WriteAllBytes(fileEncrypted, bytesEncrypted);
        }

        public static void DecryptFile(string filePath)
        {
            byte[] bytesToBeDecrypted = File.ReadAllBytes(filePath);
            byte[] passwordBytesDECR = new Byte[2]; //Encoding.UTF8.GetBytes(password);

            for (int i = 0; i < 2; ++i)
                passwordBytesDECR[i] = bytesToBeDecrypted[i];

            passwordBytesDECR = SHA256.Create().ComputeHash(passwordBytesDECR);

            byte[] bytesDecrypted = AES_Decrypt(bytesToBeDecrypted, passwordBytesDECR);

            string file = "decrypted_" + filePath.Split('\\')[filePath.Split('\\').Length - 1];
            File.WriteAllBytes(file, bytesDecrypted);
        }
    }
}