//
//	Pong game
//
// written by mike slattery - jan 2003
//
// Simple game demonstrating use of KeyListener

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

public class Pong extends Applet implements Runnable {

	public static final int FrameWidth = 500;
	public static final int FrameHeight = 350;
	
	Thread anim;
		
	// paddle positions (right and left)
	int rpx, rpy;
	int lpx, lpy;
	// ball position and velocity
	int bx, by;
	int bdx, bdy;
	// score (and font to display score)
	int rpts = 0, lpts = 0;
	Font myFont;
	
	Image buffer;
	Graphics bufgr;
	
	// Keep state of input keys 
	boolean rup = false;
	boolean rdown = false;
	boolean lup = false;
	boolean ldown = false;
	
	public void init()
	{
		bx = 70; by = 70;
		bdx = 7; bdy = 3;
		rpx = 450; rpy = 50;
		lpx = 50; lpy = 50;
		myFont = new Font("Courier", Font.BOLD, 24);
		addKeyListener (new keyBd());
		addMouseListener (new mseL());
	}

	public void start()
	{
		anim = new Thread(this);
		anim.start();
	}
			
	public void stop()
	{
		anim = null;
	}
	
	public void update (Graphics g)
	{
		if (buffer == null)
		{
			buffer = createImage (FrameWidth, FrameHeight);
			bufgr = buffer.getGraphics();
		}
		paint(bufgr);
		g.drawImage (buffer, 0, 0, null);
	}
	
	public void paint (Graphics g)
	{
		g.clearRect(0, 0, FrameWidth, FrameHeight);
		// Draw ball
		g.setColor(Color.red);
		g.fillOval(bx-10, by-10, 20, 20);
		// Draw paddles
		g.setColor(Color.blue);
		g.fillRect(rpx-4, rpy, 8, 30);
		g.fillRect(lpx-4, lpy, 8, 30);
		// Write score
		g.setColor(Color.black);
		g.setFont(myFont);
		g.drawString(""+lpts,80,310);
		g.drawString(""+rpts,340,310);
	}
	
	// thread starting point
	public void run ()
	{
		while(anim != null)
		{
			// Move ball & paddles here and check for
			// collision of ball with walls & paddles
			//
			bx += bdx; by += bdy;
			// Check if the ball is past a paddle
			// and so one side scores
			if (bx < 20)
			{
				rpts++;
				bx = 430; by = (int)(70+20*Math.random());
				bdx = -7; bdy = 4;
			}
			if (bx > Pong.FrameWidth-20)
			{
				lpts++;
				bx = 70; by = (int)(70+20*Math.random());
				bdx = 7; bdy = 4;
			}
			// Check for bounce off top or bottom
			if (by < 30)
				bdy = -bdy;
			if (by > 270)
				bdy = -bdy;

			// Update paddles
			// Check each of the possible inputs
			if (rup)
			{
				if (rpy > 24)
					rpy -= 4;
			}
			if (rdown)
			{
				if (rpy < 296)
					rpy += 4;
			}
			if (lup)
			{
				if (lpy > 24)
					lpy -= 4;
			}
			if (ldown)
			{
				if (lpy < 296)
					lpy += 4;
			}
			/*
			 * Check for paddles hitting ball
			 */
			if ((Math.abs(rpx-bx) < 14) && (by > rpy-10) && (by < rpy +40))
				bdx = -bdx;
			if ((Math.abs(lpx-bx) < 14) && (by > lpy-10) && (by < lpy+40))
				bdx = -bdx;

			repaint();
	
			try
			{
				Thread.sleep(30);
			} catch (InterruptedException e)
				{System.err.println("Sleep catch:"+e);}
		}
	}
	
	private class keyBd extends KeyAdapter
	{
		public void keyPressed (KeyEvent e)
		{
			int code = e.getKeyCode();
			switch (code)
			{
				case KeyEvent.VK_SEMICOLON: rup = true; break;
				case KeyEvent.VK_PERIOD: rdown = true; break;
				case KeyEvent.VK_A: lup = true; break;
				case KeyEvent.VK_Z: ldown = true; break;
			}
		}

		public void keyReleased (KeyEvent e)
		{
			int code = e.getKeyCode();
			switch (code)
			{
				case KeyEvent.VK_SEMICOLON: rup = false; break;
				case KeyEvent.VK_PERIOD: rdown = false; break;
				case KeyEvent.VK_A: lup = false; break;
				case KeyEvent.VK_Z: ldown = false; break;
			}
		}
	}
	//
	// This is just a minimal mouse handler to allow us
	// to get keyboard focus (needed to receive keyboard
	// events).
	//
	private class mseL extends MouseAdapter
	{
		public void mouseClicked(MouseEvent e)
		{
			requestFocus();
		}
	}
}