import javax.swing.*;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

public class Canvas extends JFrame {
    private static final int CANVAS_WIDTH = 500;
    private static final int CANVAS_HEIGHT = 500;

    private static final int AU_LINE_HEIGHT = CANVAS_HEIGHT/4*3;

    private int crashes = 0;

    private int x1;
    private int x2;
    private int y1;
    private int y2;


    private int line = 0;

    private final DrawCanvas canvas;

    public Canvas() {
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
        this.pack();
        this.setSize(CANVAS_WIDTH,CANVAS_HEIGHT);
        this.setLocationRelativeTo(null);
        this.setTitle("Canvas Desktop");
        this.setVisible(true);
        this.canvas = new DrawCanvas();
        this.canvas.setPreferredSize(new Dimension(CANVAS_WIDTH, CANVAS_HEIGHT));

        add(canvas);

        addKeyListener(new KeyListener() {
            @Override
            public void keyTyped(KeyEvent e) {

            }

            @Override
            public void keyPressed(KeyEvent e) {
                if (e.getKeyCode() == KeyEvent.VK_DOWN)
                {
                    System.out.println("Zmáčknuto tlačítko DOWN");
                    if (line >= AU_LINE_HEIGHT)
                    {
                        if (crashes == 0) {
                            System.out.println("succes");
                            crashes++;
                            x1 = CANVAS_WIDTH/2;
                            x2 = CANVAS_WIDTH/2;
                            y1 = line;
                            y2 = line;
                        }

                        x1 += 10;
                        y1 -= 10;

                        x2 -= 10;
                        y2 -= 10;

                        System.out.println(x1);
                        System.out.println(x2);
                        System.out.println(y1);
                        System.out.println(y2);
                        repaint();



                    }
                    else {
                        line += 10;
                        repaint();
                    }

                }
            }

            @Override
            public void keyReleased(KeyEvent e) {

            }
        });

    }

    public class DrawCanvas extends JPanel
    {
        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            setBackground(Color.BLUE);
            g.drawLine(CANVAS_WIDTH/2,0,CANVAS_WIDTH/2,line);
            g.drawLine(0,AU_LINE_HEIGHT, CANVAS_WIDTH, AU_LINE_HEIGHT);
            System.out.println(crashes);
            if (crashes > 0) {
                g.drawLine(CANVAS_WIDTH/2,line, x1, y1);
                g.drawLine(CANVAS_WIDTH/2,line, x2, y2);
            }
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Canvas();
            }
        });
    }
}