using System;
using System.Text;
using System.Windows.Forms;
using System.Security.Cryptography;

namespace WinFormsApp1
{
    public class CountdownForm : Form
    {
        private readonly Label _label;
        private readonly System.Windows.Forms.Timer _timer;
        private int _seconds = 2592000;

        private static readonly byte[] Key = Convert.FromBase64String("T9muLMd0UpRYgb99ZqihElEuegrsWFtvA6c88wznaRw=");
        private static readonly byte[] IV = Convert.FromBase64String("wljtQ0QGd4NNOU+5VvMjlw==");
        private static readonly byte[] Cipher = Convert.FromBase64String("3YfjykEeazHsGKp5hykYgzYWa+HXaT5c6PtYPfNB9B8=");

        public CountdownForm()
        {
            Text = "Time Machine";
            StartPosition = FormStartPosition.CenterScreen;
            ClientSize = new System.Drawing.Size(800, 150);

            _label = new Label
            {
                Dock = DockStyle.Fill,
                TextAlign = System.Drawing.ContentAlignment.MiddleCenter,
                Font = new System.Drawing.Font("Segoe UI", 14f, System.Drawing.FontStyle.Bold),
                Text = "Wait " + _seconds.ToString() + " seconds for flag to be revealed"
            };
            Controls.Add(_label);

            _timer = new System.Windows.Forms.Timer { Interval = 1000 };
            _timer.Tick += OnTick;
        }

        protected override void OnShown(EventArgs e)
        {
            base.OnShown(e);
            _timer.Start();
        }

        private void OnTick(object? sender, EventArgs e)
        {
            _seconds--;
            if (_seconds > 0)
            {
                _label.Text = "Wait " + _seconds.ToString() + " seconds for flag to be revealed";
            }
            else
            {
                _timer.Stop();
                _label.Text = DecryptFlag();
            }
        }

        private static string DecryptFlag()
        {
            using var aes = Aes.Create();
            aes.Key = Key;
            aes.IV = IV;
            aes.Padding = PaddingMode.PKCS7;

            using var decryptor = aes.CreateDecryptor();
            var plaintextBytes = decryptor.TransformFinalBlock(Cipher, 0, Cipher.Length);
            return Encoding.UTF8.GetString(plaintextBytes);
        }
    }
}