// See https://aka.ms/new-console-template for more information
using System.Security.Cryptography;

string keyBase64;
string cipherText;
string vectorBase64;
string plainText;

Console.WriteLine("Welcome to the Aes Encryption/Decryption tool");
Select:
Console.WriteLine("Please select the action you want to perform: /n Press 1 to Generate Key. /n Press 2 to Encrypt using the key. /n Press 3 to Decrpt using the key.");

string? action = Console.ReadLine();

if (action == null || !int.TryParse(action, out int actionId) || !new List<int>{ 1, 2, 3 }.Contains(actionId))
{
    Console.WriteLine("Invalid option. /n");
    goto Select;
}

switch (actionId)
{
    case 1:
            Console.WriteLine("Creating Aes Encryption 256 bit key");
            using (Aes aesAlgorithm = Aes.Create())
            {
                aesAlgorithm.KeySize = 256;
                aesAlgorithm.GenerateKey();
                keyBase64 = Convert.ToBase64String(aesAlgorithm.Key);
                Console.WriteLine($"Aes Key Size : {aesAlgorithm.KeySize}");
                Console.WriteLine("Here is the Aes key in Base64:");
                Console.WriteLine(keyBase64);
            }
            break;
    case 2:
        Console.WriteLine("Encrypt Text");
        Console.WriteLine("Provide the Aes Key in base64 format :");
        keyBase64 = Console.ReadLine();
        Console.WriteLine("--------------------------------------------------------------");
        Console.WriteLine("Please enter the text that you want to encrypt:");
        plainText = Console.ReadLine();
        Console.WriteLine("--------------------------------------------------------------");
        cipherText = EncryptDataWithAes(plainText, keyBase64, out vectorBase64);

        Console.WriteLine("--------------------------------------------------------------");
        Console.WriteLine("Here is the cipher text with vector:");
        Console.WriteLine(cipherText + ":" + vectorBase64);
        break;
    case 3:
        Console.WriteLine("Please enter the text that you want to decrypt:");
        cipherText = Console.ReadLine();
        Console.WriteLine("--------------------------------------------------------------");

        Console.WriteLine("Provide the Aes Key:");
        keyBase64 = Console.ReadLine();
        Console.WriteLine("--------------------------------------------------------------");

        vectorBase64 = cipherText.Split(":")[1];
        cipherText = cipherText.Split(":")[0];

        plainText = DecryptDataWithAes(cipherText, keyBase64, vectorBase64);

        Console.WriteLine("--------------------------------------------------------------");
        Console.WriteLine("Here is the decrypted data:");
        Console.WriteLine(plainText);
        break;
}

goto Select;


static string EncryptDataWithAes(string plainText, string keyBase64, out string vectorBase64)
{
    using (Aes aesAlgorithm = Aes.Create())
    {
        aesAlgorithm.Key = Convert.FromBase64String(keyBase64);
        aesAlgorithm.GenerateIV();
        Console.WriteLine($"Aes Cipher Mode : {aesAlgorithm.Mode}");
        Console.WriteLine($"Aes Padding Mode: {aesAlgorithm.Padding}");
        Console.WriteLine($"Aes Key Size : {aesAlgorithm.KeySize}");

        //set the parameters with out keyword
        vectorBase64 = Convert.ToBase64String(aesAlgorithm.IV);

        // Create encryptor object
        ICryptoTransform encryptor = aesAlgorithm.CreateEncryptor();

        byte[] encryptedData;

        //Encryption will be done in a memory stream through a CryptoStream object
        using (MemoryStream ms = new MemoryStream())
        {
            using (CryptoStream cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
            {
                using (StreamWriter sw = new StreamWriter(cs))
                {
                    sw.Write(plainText);
                }
                encryptedData = ms.ToArray();
            }
        }

        return Convert.ToBase64String(encryptedData);
    }
}

static string DecryptDataWithAes(string cipherText, string keyBase64, string vectorBase64)
{
    using (Aes aesAlgorithm = Aes.Create())
    {
        aesAlgorithm.Key = Convert.FromBase64String(keyBase64);
        aesAlgorithm.IV = Convert.FromBase64String(vectorBase64);

        Console.WriteLine($"Aes Cipher Mode : {aesAlgorithm.Mode}");
        Console.WriteLine($"Aes Padding Mode: {aesAlgorithm.Padding}");
        Console.WriteLine($"Aes Key Size : {aesAlgorithm.KeySize}");
        Console.WriteLine($"Aes Block Size : {aesAlgorithm.BlockSize}");


        // Create decryptor object
        ICryptoTransform decryptor = aesAlgorithm.CreateDecryptor();

        byte[] cipher = Convert.FromBase64String(cipherText);

        //Decryption will be done in a memory stream through a CryptoStream object
        using (MemoryStream ms = new MemoryStream(cipher))
        {
            using (CryptoStream cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Read))
            {
                using (StreamReader sr = new StreamReader(cs))
                {
                    return sr.ReadToEnd();
                }
            }
        }
    }
}