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

public class TrafficSignal extends JPanel implements ActionListener {
    private static final int INITIAL_WIDTH = 100;
    private static final int INITIAL_HEIGHT = 200;

    private static final double BOX_START_X = 0.2;
    private static final double BOX_START_Y = 0.1;
    private static final double BOX_WIDTH = 0.6;
    private static final double BOX_HEIGHT = 0.8;

    private static final double BALL_HEIGHT = 0.2;
    private static final double BALL_WIDTH = 0.4;

    private static final double BALL_START_X = 0.3;

    private static final double RED_START_Y = 0.15;
    private static final double YELLOW_START_Y = 0.40;
    private static final double GREEN_START_Y = 0.65;

    public enum State {RED, YELLOW_TO_GREEN, GREEN, YELLOW_TO_RED}

    private State state;
    private Timer timer;

    private int[] intervals;

    public TrafficSignal(int intervalRed, int intervalYellow, int intervalGreen) {
        state = State.RED;
        intervals = new int[] {intervalRed, intervalYellow, intervalGreen};
        setPreferredSize(new Dimension(INITIAL_WIDTH, INITIAL_HEIGHT));
        timer = new Timer(intervalRed, this);
        timer.setRepeats(false);
        timer.start();
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        int width = getWidth();
        int height = getHeight();

        // draw black box
        g.setColor(Color.BLACK);
        g.fillRect((int)(width*BOX_START_X), (int)(height*BOX_START_Y),
                    (int)(width*BOX_WIDTH), (int)(height*BOX_HEIGHT));

        int ballWidth = (int)(width*BALL_WIDTH);
        int ballHeight = (int)(height*BALL_HEIGHT);
        int ballStartX = (int)(width*BALL_START_X);

        switch (state) {
            case RED:        
                g.setColor(Color.RED);
                g.fillOval(ballStartX, (int)(height*RED_START_Y),
                            ballWidth, ballHeight);
                break;
            case YELLOW_TO_GREEN:
            case YELLOW_TO_RED:
                g.setColor(Color.YELLOW);
                g.fillOval(ballStartX, (int)(height*YELLOW_START_Y),
                            ballWidth, ballHeight);
                break;
            case GREEN:
                g.setColor(Color.GREEN);
                g.fillOval(ballStartX, (int)(height*GREEN_START_Y),
                            ballWidth, ballHeight);
                break;
        }
    }

    public void actionPerformed(ActionEvent e) {
        state = State.values()[(state.ordinal() + 1) % State.values().length];
        switch (state) {
            case RED:
                //timer.stop();
                timer.setInitialDelay(intervals[0]);
                timer.start();
                break;
            case YELLOW_TO_GREEN:
            case YELLOW_TO_RED:
                //timer.stop();
                timer.setInitialDelay(intervals[1]);
                timer.start();
                break;
            case GREEN:
                //timer.stop();
                timer.setInitialDelay(intervals[2]);
                timer.start();
                break;
        }
        repaint();
    }

    public static void main(String[] args) {
        JFrame fr = new JFrame();
        fr.add(new TrafficSignal(1500,100,1500), BorderLayout.CENTER);
        fr.pack();
        fr.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        fr.setVisible(true);
    }

}