using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApp11
{
    public partial class Form1 : Form
    {
        //public static Nullable<Boolean>[,] grid = new Nullable<Boolean>[3, 3];
        public static char[,] grid = new char[3, 3];

        public static int W_UNIT;
        public static int H_UNIT;


        public Form1()
        {
            InitializeComponent();

            W_UNIT = Canvas.Width / 3;
            H_UNIT = Canvas.Height / 3;
        }

        private void Canvas_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = e.Graphics;

            // Draw the Board
            using (Pen myPen = new Pen(Color.Gold))
            {
                g.DrawLine(myPen, Canvas.Width / 3, 0, Canvas.Width / 3, Canvas.Height);
                g.DrawLine(myPen, (2 * Canvas.Width / 3), 0, (2 * Canvas.Width / 3), Canvas.Height);

                g.DrawLine(myPen, 0, Canvas.Height / 3, Canvas.Width, Canvas.Height / 3);
                g.DrawLine(myPen, 0, (2 * Canvas.Height / 3), Canvas.Width, (2 * Canvas.Height / 3));

                for (int i = 0; i < 3; i++)
                    for (int j = 0; j < 3; j++)
                    {
                        // Draw the X's and O's
                        if (grid[j, i] == 'X') // Then draw an X
                        {
                            g.DrawLine(myPen, (i * Canvas.Height / 3) + (j * Canvas.Width / 3), 0 + (i * Canvas.Height / 3),
                                              W_UNIT + (j * Canvas.Width / 3), H_UNIT + (i * Canvas.Height / 3));
                            g.DrawLine(myPen, (j * Canvas.Width / 3), H_UNIT + (i * Canvas.Height / 3),
                                              W_UNIT + (j * Canvas.Width / 3), (i * Canvas.Height / 3));
                        }
                    }
            }
        }

        private void Canvas_MouseDown(object sender, MouseEventArgs e)
        {
            /*
             * We can now know where the user has clicked on the Board
            MessageBox.Show("[" + e.X / (Canvas.Width / 3) + ", " + 
                                  e.Y / (Canvas.Height / 3) + "]");
            */
            grid[e.X / (Canvas.Width / 3), e.Y / (Canvas.Height / 3)] = 'X';
            Canvas.Refresh();
        }
    }
}