// ReboundGUI.java
//   Animation with event listener (mouse and timer)
//   Descended from Lewis/Loftus example
// The timer does the animation by repainting every DELAY msecs
// in a newly computed position, reversing direction when the border
// is bumped. The mouse is used to stop the animation and restart it
// with a steeper angle of travel (up to a limit, then back to horizontal).

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

public class ReboundGUI extends JPanel {
    private final int IMAGE_SIZE = 35, DELAY = 20;
    private final int PIXELS = 3; // Distance to move X

    private ImageIcon image;
    private Timer timer;
    private int x, y, dirX, dirY; // coordinates and direction
    private int rise; // Distance to move Y

    // Start the GUI in a window
    public static void main(String[] args) {
        JFrame frame = new JFrame("Rebound");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().add(new ReboundGUI());
        frame.pack();
        frame.setVisible(true);
    }


    /** Constructor sets up the GUI, including the timer for the animation */
    public ReboundGUI() {
        addMouseListener(new ReboundMouseListener());

        timer = new Timer(DELAY, new ReboundActionListener());

        image = new ImageIcon("happyface.gif");

	// Inital coordiantes, direction, angle
        x = 0;
        y = IMAGE_SIZE;
        dirX = 1;
        dirY = 1;
        rise = PIXELS;

        setPreferredSize(new Dimension(300, 200));
        setBackground(Color.black);
        timer.start();
    }

    /** Draws the image in the current location */
    public void paintComponent(Graphics page) {
        super.paintComponent(page);
        image.paintIcon(this, page, x, y);
    }

    /**  Start or stop the animation and change angle */
    private void toggleAnimation() {
        // If timer is going, stop it; if stopped, start it
        if (timer.isRunning())
            timer.stop();
        else {
            // Change the rise
	    rise = (rise + 1) % (3*PIXELS);
            timer.start();
	}
    }

    // Private inner class for the action listener for the timer
    private class ReboundActionListener implements ActionListener {
        //  Updates the position of the image and possibly the direction
        //  of movement whenever the timer fires an action event.
        public void actionPerformed(ActionEvent event) {
             x += dirX * PIXELS;
             y += dirY * rise;

	    // Reverse if bumping border
            if (x <= 0 || x >= getWidth()-IMAGE_SIZE)
                dirX = dirX * -1;
            if (y <= 0 || y >= getHeight()-IMAGE_SIZE)
                dirY = dirY * -1;
            
            repaint();

        }

    }

    // Private inner class for the mouse listener for the gui
    private class ReboundMouseListener implements MouseListener {
        //  Stops or starts the timer (and therefore the animation)
        //  when the mouse button is clicked.
        public void mouseClicked(MouseEvent event) {
            toggleAnimation();
        }

        //  Provide empty definitions for unused event methods.
        public void mouseEntered (MouseEvent event) {}
        public void mouseExited (MouseEvent event) {}
        public void mousePressed (MouseEvent event) {}
        public void mouseReleased (MouseEvent event) {}

    }
}