using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Text;
using System.Threading.Tasks;
using System.Timers;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApp1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private CounterViewModel _counterViewModel = new CounterViewModel();

        public MainWindow()
        {
            InitializeComponent();
            DataContext = _counterViewModel;
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            _counterViewModel.Start();
        }

        public class CounterViewModel : INotifyPropertyChanged
        {
            public int SecToCount { get; set; }
            public DateTime FinishTime { get; set; }
            public TimeSpan Counter
            {
                get
                {
                    if (!Enabled)
                        return TimeSpan.Zero;

                    var res = FinishTime -DateTime.Now;
                    if(res <= TimeSpan.Zero)
                    {
                        Enabled = false;
                        return TimeSpan.Zero;
                    }
                    return res;
                }
            }

            private bool _enabled;
            public bool Disabled => !Enabled;

            public bool Enabled
            {
                get => _enabled;
                set {
                    if (value == _enabled)
                        return;

                    _enabled = value;
                    _timer.Start();
                    OnPropertyChanged();
                    OnPropertyChanged(nameof(Disabled));
                }
            }


            private Timer _timer = new Timer
            {
                Interval = 1000
            };

            public event PropertyChangedEventHandler PropertyChanged;

            public CounterViewModel()
            {
                _timer.Elapsed += (sender, args) => OnPropertyChanged(nameof(Counter));
            }

            private void OnPropertyChanged([CallerMemberName] string memberName = "")
            {
                PropertyChanged?.Invoke(sender: this, new PropertyChangedEventArgs(memberName));
            }
            public void Start()
            {
                FinishTime = DateTime.Now.AddSeconds(SecToCount);
                Enabled = true;
            }
        }


    }
}