//
//  Pon.java
//

import java.awt.*;
import java.awt.event.*;
import java.applet.*;

public class Pon extends Applet implements Runnable {
	
	Pad[] pad=new Pad[2];
	Ball ball;
	Player player;
	Computer computer;
	Image offscreen;
	Graphics og;
	
    public void init() {
                            setBackground(Color.white);
		pad[0]=new Pad(getSize().width/20,getSize().height*3/8,getSize().width/20,getSize().height/4);
		pad[1]=new Pad(getSize().width*18/20,getSize().height*3/8,getSize().width/20,getSize().height/4);
		ball=new Ball(getSize().width/2,getSize().height/2,getSize().width/20,(Math.random()>0?1:-1)*getSize().width/50,0);
		player=new Player(this,pad[0],ball);
		computer=new Computer(this,pad[1],ball);
		new Thread(this).start();
    }
	
	public void update(Graphics g) {
		paint(g);
	}
	
	public void paint(Graphics g) {
		if (offscreen==null) {
			offscreen=createImage(getSize().width,getSize().height);
			og=offscreen.getGraphics();
		}
		og.clearRect(0,0,getSize().width,getSize().height);
		for (int i=0;i<2;i++)
			og.fillRect(pad[i].x,pad[i].y,pad[i].width,pad[i].height);
		og.fillOval(ball.x-ball.radius/2,ball.y-ball.radius/2,ball.radius,ball.radius);
		g.drawImage(offscreen,0,0,this);
	}
	
	void move(Pad pad,int y) {
		if (pad.y!=y) {
			pad.y=y;
			if (pad.y<0)
				pad.y=0;
			else if (pad.y+pad.height>getSize().height)
				pad.y=getSize().height-pad.height;
			repaint();
		}
	}
	
	public void run() {
		while (true) {
			ball.x+=ball.dx;
			ball.y+=ball.dy;
			if (pad[0].contains(ball)) {
				ball.dx=Math.abs(ball.dx);
				ball.dy+=(ball.y-pad[0].y-pad[0].height/2)/10;
			} else if (pad[1].contains(ball)) {
				ball.dx=-Math.abs(ball.dx);
				ball.dy+=(ball.y-pad[1].y-pad[1].height/2)/10;
			} else if (ball.x<0) {
				ball.x=pad[1].x+pad[1].width/2;
				ball.y=pad[1].y+pad[1].height/2;
				ball.dx=-Math.abs(ball.dx);
				ball.dy/=2;
			} else if (ball.x>getSize().width) {
				ball.x=pad[0].x+pad[0].width/2;
				ball.y=pad[0].y+pad[0].height/2;
				ball.dx=Math.abs(ball.dx);
				ball.dy/=2;
			}
			if (ball.y<0)
				ball.dy=Math.abs(ball.dy);
			else if (ball.y>getSize().height)
				ball.dy=-Math.abs(ball.dy);
			repaint();
			try {
				Thread.sleep(50);
			} catch (InterruptedException e) {
			}
		}
	}
}

class Pad extends Rectangle {
	Pad(int x,int y,int width,int height) {
		super(x,y,width,height);
	}
}

class Ball extends Point {
	
	int radius;
	int dx,dy;
	
	Ball(int x,int y,int radius,int dx,int dy) {
		super(x,y);
		this.radius=radius;
		this.dx=dx;
		this.dy=dy;
	}
}

class Player implements MouseMotionListener {
	Pon mediator;
	Pad pad;
	Ball ball;
	Player(Pon pon,Pad pad,Ball ball) {
		mediator=pon;
		this.pad=pad;
		this.ball=ball;
		mediator.addMouseMotionListener(this);
	}
	public void mouseDragged(MouseEvent evt) {
		mediator.move(pad,evt.getY()-pad.height/2);
	}
	public void mouseMoved(MouseEvent evt) {
		mediator.move(pad,evt.getY()-pad.height/2);
	}
}

class Computer implements Runnable {
	Pon mediator;
	Pad pad;
	Ball ball;
	Computer(Pon pon,Pad pad,Ball ball) {
		mediator=pon;
		this.pad=pad;
		this.ball=ball;
		new Thread(this).start();
	}
	public void run() {
		while (true) {
			mediator.move(pad,pad.y+Math.max(-pad.height/7,Math.min(ball.y-pad.height/2-pad.y,pad.height/7)));
			try {
				Thread.sleep(150);
			} catch (InterruptedException e) {
			}
		}
	}
}