using Org.BouncyCastle.Crypto;
using Org.BouncyCastle.Crypto.IO;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Security;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace PasswortEncryptor
{
    public partial class MainForm : Form
    {
        private static string MemoryMasterKey = "!ZEqy2Zsb#VK6<8`H6;W~VxJ$r:w.{ffzwDt=<yKC6m6N3;T<9nyeF&+.4&D@rhK";

        public MainForm()
        {
            InitializeComponent();
        }

        public static string Encrypt(string value)
        {
            string result = null;

            try
            {  
                IBufferedCipher encCipher = CipherUtilities.GetCipher("AES/GCM/NoPadding");
                byte[] keyBytes = GetKey(MemoryMasterKey);
                KeyParameter key = new KeyParameter(keyBytes); 
                byte[] nonce = new byte[12];
                RandomNumberGenerator.Create().GetBytes(nonce);
                encCipher.Init(true, new ParametersWithIV(key, nonce));                
                byte[] plainText = Encoding.UTF8.GetBytes(value);
                byte[] chiperBuffer = null;
                byte[] tag = new byte[16];
                byte[] resultBuffer = null;

                using (MemoryStream memStream = new MemoryStream())
                {
                    using (CipherStream encStream = new CipherStream(memStream, null, encCipher))
                    {
                        encStream.Write(plainText, 0, plainText.Length);
                    }

                    chiperBuffer = memStream.ToArray();

                    resultBuffer = nonce.Concat(chiperBuffer).ToArray();
                }
              
                result = Convert.ToBase64String(resultBuffer);
            }
            catch 
            {
                result = null;
            }

            return result;
        }

        public static string Decrypt(string value)
        {
            string result = null;

            try
            {
                IBufferedCipher decCipher = CipherUtilities.GetCipher("AES/GCM/NoPadding");
                byte[] keyBytes = GetKey(MemoryMasterKey);
                KeyParameter key = new KeyParameter(keyBytes);
                byte[] combined = Convert.FromBase64String(value);
                byte[] tag = combined.Skip(combined.Length - 16).ToArray();
                byte[] nonce = combined.Take(12).ToArray();
                byte[] chiperText = combined.Skip(nonce.Length).Take(combined.Length - nonce.Length).ToArray();
                byte[] plainTextBuffer = null;

                decCipher.Init(false, new ParametersWithIV(key, nonce));

                using (MemoryStream memStream = new MemoryStream(chiperText, false))
                {
                    MemoryStream dataStream = new MemoryStream();

                    using (dataStream)
                    {
                        using (CipherStream decStream = new CipherStream(memStream, (IBufferedCipher)decCipher, null))
                        {
                            int ch;

                            while ((ch = decStream.ReadByte()) >= 0)
                            {
                                dataStream.WriteByte((byte)ch);
                            }
                        }
                    }

                    plainTextBuffer = dataStream.ToArray();

                    result = Encoding.UTF8.GetString(plainTextBuffer);
                }
            }
            catch
            {
                result = null;
            }

            return result;
        }

        public static byte[] GetKey(string password)
        {
            byte[] result = null;

            try
            {
                if (!string.IsNullOrEmpty(password))
                {
                    if (password.Length < 32)
                    {
                        password = password.PadRight(32, '@');
                    }
                    else if (password.Length > 32)
                    {
                        password = MD5Encrypt(password);
                    }

                    result = Encoding.ASCII.GetBytes(password);
                }
            }
            catch (Exception ex)
            {
               
            }

            return result;
        }

        public static string MD5Encrypt(string value)
        {
            string result = null;

            try
            {
                byte[] bytes = Encoding.UTF8.GetBytes(value);

                using (System.Security.Cryptography.MD5 hash = System.Security.Cryptography.MD5.Create())
                {
                    byte[] hashedInputBytes = hash.ComputeHash(bytes);

                    StringBuilder hashedInputStringBuilder = new StringBuilder(128);

                    foreach (var b in hashedInputBytes)
                    {
                        hashedInputStringBuilder.Append(b.ToString("X2"));
                    }

                    result = hashedInputStringBuilder.ToString().ToLower();
                }
            }
            catch
            {
                result = null;
            }

            return result;
        }

        private void cbxTemplate_SelectedIndexChanged(object sender, EventArgs e)
        {
            if(cbxTemplate.SelectedIndex == 1)
            {
                txtInput.Text = "Server=myServer;Uid=myUser;Database=myDatabase;Pwd=myPassword;SSLMode=None;Charset=utf8mb4";
            }
        }

        private void btnEncrypt_Click(object sender, EventArgs e)
        {
            try
            {
                txtOutput.Text = Encrypt(txtInput.Text);
            }
            catch (Exception ex)
            {
                txtOutput.Text = ex.Message;
            }
        }
    }
}