using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
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 WPFCanvas
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private enum DrawMode
        {
            Line,
            Circle,
            Square,
            Eraser,
        };

        private bool _mouseClicked;
        private Point _prePosition;

        private Brush _myBrush;
        private double _thickness;

        private Rectangle _tmpRect;

        private DrawMode MODE;

        public MainWindow()
        {
            InitializeComponent();
        }

        private void btnLine_Click(object sender, RoutedEventArgs e)
        {
            MODE = DrawMode.Line;
        }

        private void Window_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
        {
            _mouseClicked = true;
            _prePosition = e.GetPosition(canvas);
        }

        private void Window_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
        {
            _mouseClicked = false;
        }

        private void Window_MouseMove(object sender, MouseEventArgs e)
        {
            Point nowPosition = e.GetPosition(canvas);
            if (!_mouseClicked)
                return;

            switch (MODE)
            {
                case DrawMode.Line:
                    Line line = new Line()
                    {
                        X1 = _prePosition.X,
                        Y1 = _prePosition.Y,
                        X2 = nowPosition.X,
                        Y2 = nowPosition.Y,
                        Stroke = _myBrush == null ? Brushes.Black : _myBrush,
                        StrokeThickness = _thickness <= 0 ? 1 : _thickness
                    };
                    canvas.Children.Add(line);

                    _prePosition = nowPosition;
                    break;
                case DrawMode.Square:
                    if (e.MouseDevice.LeftButton != MouseButtonState.Pressed)
                        _tmpRect = null;
                    else
                    {
                        Rectangle rect = new Rectangle();
                        rect.Stroke = Brushes.Gray;
                        rect.Fill = _myBrush == null ? Brushes.Black : _myBrush;
                        rect.Opacity = 0.8;

                        double left = _prePosition.X;
                        double top = _prePosition.Y;

                        double width = nowPosition.X - _prePosition.X;
                        double height = nowPosition.Y - _prePosition.Y;

                        if (nowPosition.X < _prePosition.X)
                        {
                            left = nowPosition.X;
                            width *= -1;
                        }

                        if (nowPosition.Y < _prePosition.Y)
                        {
                            top = nowPosition.Y;
                            height *= -1;
                        }

                        rect.Margin = new Thickness(left, top, 0, 0);
                        rect.Width = width;
                        rect.Height = height;

                        canvas.Children.Remove(_tmpRect);
                        _tmpRect = rect;
                        canvas.Children.Add(rect);
                    }
                    break;
            }

            
        }

        private void btnBlack_Click(object sender, RoutedEventArgs e)
        {
            _myBrush = Brushes.Black;
        }

        private void btnRed_Click(object sender, RoutedEventArgs e)
        {
            _myBrush = Brushes.Red;
        }

        private void btnBlue_Click(object sender, RoutedEventArgs e)
        {
            _myBrush = Brushes.Blue;
        }

        private void btnGreen_Click(object sender, RoutedEventArgs e)
        {
            _myBrush = Brushes.Green;
        }

        private void btnYellow_Click(object sender, RoutedEventArgs e)
        {
            _myBrush = Brushes.Yellow;
        }

        private void cboThickness_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            _thickness = double.Parse(cboThickness.SelectedValue.ToString());
        }

        private void btnSquare_Click(object sender, RoutedEventArgs e)
        {
            MODE = DrawMode.Square;
        }
    }
}