import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JApplet;

public class Bong extends JApplet implements Runnable, KeyListener {
	private Thread thread = null;
	private double x, dx, y, dy;
	private int xSize, ySize;
	private double paddleXL, paddleYL, paddleXR, paddleYR;
	private double paddleSize;
	private String message;
	private Font font;

	@Override
	public void init() {
		xSize = 480; ySize = 360;
		paddleSize = 20;
		message = "Game started!";
		font = new Font("Monospaced", Font.PLAIN, 12);
		addKeyListener(this);
	}

	private void initialize() {
		x = 100; y = 100;
		dx = 16; dy = 10;
		paddleYL = paddleYR = ySize/2;
		paddleXL = 30; paddleXR = xSize-30;
	}

	@Override
	public void paint(Graphics g) {
		super.paint(g);
		g.setColor(Color.BLACK);
		g.drawRect(0, 0, xSize-1, ySize-1);
		g.setColor(Color.MAGENTA.darker());
		g.fillOval((int)(x-3), (int)(y-3), 6, 6);
		
		g.setColor(Color.RED);
		g.fillRect((int)(paddleXL-2), (int)(paddleYL-paddleSize/2), 4, (int)paddleSize);
		g.setColor(Color.BLUE);
		g.fillRect((int)(paddleXR-2), (int)(paddleYR-paddleSize/2), 4, (int)paddleSize);

		g.setFont(font);
		g.setColor(Color.GREEN.darker());
		g.drawString(message, 5, ySize+12);
		g.setColor(Color.RED.darker());
		g.drawString("Left:  Z(D), W(U)", 5, ySize+24);
		g.setColor(Color.BLUE.darker());
		g.drawString("Right: M(D), I(U)", 5, ySize+36);	
	}

	public void run() {
		Thread thisThread = Thread.currentThread();
		while (thread==thisThread) {
			initialize();
			requestFocus();
			while (true) {
				x += dx;  y += dy;
				if (dx<0 && (x-paddleXL)*(x-dx-paddleXL)<=0) {
					double rY = y+dy*(paddleXL-x)/dx;
					if ((rY-paddleYL+paddleSize/2)*(rY-paddleYL-paddleSize/2)<=0) {
						x = 2*paddleXL-x;
						dx *= -1;
					}
				}
				if (x<0) {
					x = -x;
					dx*=-1;
					message = "R won!";
				}
				if (dx>0 && (x-paddleXR)*(x-dx-paddleXR)<=0) {
					double rY = y+dy*(paddleXR-x)/dx;
					if ((rY-paddleYR+paddleSize/2)*(rY-paddleYR-paddleSize/2)<=0) {
						x = 2*paddleXR-x;
						dx *= -1;
					}
				}
				if (x>xSize) {
					x = 2*xSize - x;
					dx*=-1;
					message = "L won!";
				}
				if (y<0) {
					y = -y;
					dy*=-1;
				}
				if (y>ySize) {
					y = 2*ySize - y;
					dy*=-1;
				}
				repaint();
				try {
					Thread.sleep(250);
				} catch (InterruptedException e) {
				}
			}
		}	
	}

	@Override
	public void start() {
		if (thread==null) {
			thread = new Thread(this);
			thread.start();
		}
	}

	@Override
	public void stop() {
		thread = null;
	}

	public void keyPressed(KeyEvent e) {
		int key = e.getKeyCode();
		switch (key) {
		case 'W':  paddleYL -= 10; break;
		case 'Z':  paddleYL += 10; break;
		case 'I':  paddleYR -= 10; break;
		case 'M':  paddleYR += 10; break;
		}
	}

	public void keyReleased(KeyEvent e) {}
	public void keyTyped(KeyEvent e) {}
}