import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class ColorPicker extends JComponent implements Runnable {
    private Image image; // the canvas
    private Graphics2D graphics2D;  // this will enable drawing
    private int curX; // current mouse x coordinate
    private int curY; // current mouse y coordinate
    private int oldX; // previous mouse x coordinate
    private int oldY; // previous mouse y coordinate

    JButton yellowButton; // a button to change paint color
    JButton blueButton; // a button to change paint color
    JButton redButton; // a button to change paint color
    JButton greenButton; // a button to change paint color


    ColorPicker paint; // variable of the type ColorPicker

    /* action listener for buttons */
    ActionListener actionListener = new ActionListener() {
        @Override
        public void actionPerformed(ActionEvent e) {
            if (e.getSource() == yellowButton) {
                paint.yellow();
            }
            if (e.getSource() == blueButton) {
                paint.blue();
            }
            if (e.getSource() == redButton) {
                paint.red();
            }
            if (e.getSource() == greenButton) {
                paint.green();
            }

        }
    };

    /* set up paint colors */
    public void yellow() {
        graphics2D.setPaint(Color.yellow);
    }

    public void blue() {
        graphics2D.setPaint(Color.blue);
    }

    public void red() {
        graphics2D.setPaint(Color.red);
    }

    public void green() {
        graphics2D.setPaint(Color.green);
    }

    public ColorPicker() {
        addMouseListener(new MouseAdapter() {
            @Override
            public void mousePressed(MouseEvent e) {
                /* set oldX and oldY coordinates to beginning mouse press*/
                oldX = e.getX();
                oldY = e.getY();
            }
        });


        addMouseMotionListener(new MouseMotionAdapter() {
            @Override
            public void mouseDragged(MouseEvent e) {
                /* set current coordinates to where mouse is being dragged*/
                curX = e.getX();
                curY = e.getY();

                /* draw the line between old coordinates and new ones */
                graphics2D.drawLine(oldX, oldY, curX, curY);

                /* refresh frame and reset old coordinates */
                repaint();
                oldX = curX;
                oldY = curY;

            }
        });
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new ColorPicker());
    }

    public void run() {
        /* set up JFrame */
        JFrame frame = new JFrame("Debugging Exercise");
        Container content = frame.getContentPane();
        content.setLayout(new BorderLayout());
        paint = new ColorPicker();
        content.add(paint, BorderLayout.CENTER);

        yellowButton = new JButton("Yellow");
        yellowButton.addActionListener(actionListener);
        blueButton = new JButton("Blue");
        blueButton.addActionListener(actionListener);
        redButton = new JButton("Red");
        redButton.addActionListener(actionListener);
        greenButton = new JButton("Green");
        greenButton.addActionListener(actionListener);

        JPanel colorPanel = new JPanel();   // Create new panel to hold all color buttons

        // Add all color buttons to new panel
        colorPanel.add(yellowButton);
        colorPanel.add(blueButton);
        colorPanel.add(redButton);
        colorPanel.add(greenButton);

        content.add(colorPanel, BorderLayout.NORTH);    // Add the panel with buttons at top of canvas

        frame.setSize(600, 400);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);


    }

    protected void paintComponent(Graphics g) {
        if (image == null) {
            image = createImage(getSize().width, getSize().height);
            /* this lets us draw on the image (ie. the canvas)*/
            graphics2D = (Graphics2D) image.getGraphics();
            /* gives us better rendering quality for the drawing lines */
            graphics2D.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            /* set canvas to white with default paint color */
            graphics2D.setPaint(Color.white);
            graphics2D.fillRect(0, 0, getSize().width, getSize().height);
            graphics2D.setPaint(Color.black);
            repaint();
        }
        g.drawImage(image, 0, 0, null);

    }
}