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


namespace ServerCore;

public class EncryptionHelper
{
    public static string encryptTextByDES(string text, byte[] encryptKey, byte[] encryptIv)
    {
        try
        {
            // Create a MemoryStream.
            using (MemoryStream mStream = new MemoryStream())
            {
                // Create a new DES object.
                using (var des = DES.Create())
                // Create a DES encryptor from the key and IV
                using (ICryptoTransform encryptor = des.CreateEncryptor(encryptKey, encryptIv))
                // Create a CryptoStream using the MemoryStream and encryptor
                using (var cStream = new CryptoStream(mStream, encryptor, CryptoStreamMode.Write))
                {
                    // Convert the provided string to a byte array.
                    byte[] toEncrypt = Encoding.UTF8.GetBytes(text);

                    // Write the byte array to the crypto stream and flush it.
                    cStream.Write(toEncrypt, 0, toEncrypt.Length);

                    // Ending the using statement for the CryptoStream completes the encryption.
                }

                // Get an array of bytes from the MemoryStream that holds the encrypted data.
                byte[] ret = mStream.ToArray();

                // Return the encrypted buffer.
                return Convert.ToBase64String(ret);
            }
        }
        catch (CryptographicException e)
        {
            Log.getLogger().error($"Exception !!!, A Cryptographic error occurred : {e}");
            throw;
        }
    }

    public static string decryptTextByDES(string encrypted, byte[] encryptKey, byte[] encryptIv)
    {
        try
        {
            // Create a buffer to hold the decrypted data.
            // DES-encrypted data will always be slightly bigger than the decrypted data.
            //byte[] StrByte = Encoding.UTF8.GetBytes(encrypted);
            var encryptedBytes = Convert.FromBase64String(encrypted);
            byte[] decrypted = new byte[encrypted.Length];
            int offset = 0;

            // Create a new MemoryStream using the provided array of encrypted data.
            using (MemoryStream mStream = new MemoryStream(encryptedBytes))
            {
                // Create a new DES object.
                using (var des = DES.Create())
                // Create a DES decryptor from the key and IV
                using (ICryptoTransform decryptor = des.CreateDecryptor(encryptKey, encryptIv))
                // Create a CryptoStream using the MemoryStream and decryptor
                using (var cStream = new CryptoStream(mStream, decryptor, CryptoStreamMode.Read))
                {
                    // Keep reading from the CryptoStream until it finishes (returns 0).
                    int read = 1;

                    while (read > 0)
                    {
                        read = cStream.Read(decrypted, offset, decrypted.Length - offset);
                        offset += read;
                    }
                }
            }

            // Convert the buffer into a string and return it.
            return Encoding.UTF8.GetString(decrypted, 0, offset);
        }
        catch (CryptographicException e)
        {
            Log.getLogger().error($"Exception !!!, A Cryptographic error occurred : {e}");
            throw;
        }
    }


    public static string encryptTextByAES(string plainText, byte[] encryptKey, byte[] encryptIv)
    {
        // Check arguments.
        if (plainText == null || plainText.Length <= 0)
            NullReferenceCheckHelper.throwIfNull(plainText, () => $"plainText is null !!!");
        if (encryptKey == null || encryptKey.Length <= 0)
            NullReferenceCheckHelper.throwIfNull(encryptKey, () => $"encryptKey is null !!!");
        if (encryptIv == null || encryptIv.Length <= 0)
            NullReferenceCheckHelper.throwIfNull(encryptIv, () => $"encryptIv is null !!!");

        byte[] encrypted;

        // Create an Aes object
        // with the specified key and IV.
        using (Aes aesAlg = Aes.Create())
        {
            aesAlg.Key = encryptKey;
            aesAlg.IV = encryptIv;

            // Create an encryptor to perform the stream transform.
            ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

            // Create the streams used for encryption.
            using (MemoryStream msEncrypt = new MemoryStream())
            {
                using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                {
                    using (StreamWriter 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 Convert.ToBase64String(encrypted);
    }

    public static string decryptTextByAES(string cipherText, byte[] encryptKey, byte[] encryptIv)
    {
        // Check arguments.
        if (cipherText == null || cipherText.Length <= 0)
            NullReferenceCheckHelper.throwIfNull(cipherText, () => $"cipherText is null !!!");
        if (encryptKey == null || encryptKey.Length <= 0)
            NullReferenceCheckHelper.throwIfNull(encryptKey, () => $"encryptKey is null !!!");
        if (encryptIv == null || encryptIv.Length <= 0)
            NullReferenceCheckHelper.throwIfNull(encryptIv, () => $"encryptIv is null !!!");

        // Declare the string used to hold
        // the decrypted text.
        string plaintext = string.Empty;
        byte[] chipherBin = Convert.FromBase64String(cipherText);

        // Create an Aes object
        // with the specified key and IV.
        using (Aes aesAlg = Aes.Create())
        {
            aesAlg.Key = encryptKey;
            aesAlg.IV = encryptIv;

            // Create a decryptor to perform the stream transform.
            ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

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

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

        return plaintext;
    }
}