import java.applet.*;
import java.awt.*;
import java.util.*;

/**
  * General action game applet class-- has somewhat clever 
  * desired framerate system, takes care of double buffering.
  * Games derived from it need to define setupGame() (run at begining)
  * and runGame() (run every tick of the clock, game must paint 
  * current scene onscreen
  **/

abstract public class GameRunner extends Applet implements Runnable {
  
Thread animation;

Graphics offscreenGraphics;
Image offscreenImage;
int screenWidth, screenHeight; // applet dimensions
Color screenColor = Color.black; //default color, can be changed by game
long oldTime; //used for time keeping

static final int REFRESH_RATE = 30; // in ms, target time between clicks

static final int KEY_SPACE = 32;
static final int KEY_ENTER = 10;
static final int KEY_ESCAPE = 27;

public void init() {
	screenWidth = bounds().width;            // get applet dimensions
	screenHeight = bounds().height;
	offscreenImage = createImage(screenWidth,screenHeight); // make offscreenGraphics buffer
	offscreenGraphics = offscreenImage.getGraphics();

	setupGame(); //run game setup routine
	setBackground(screenColor);        // applet background
	oldTime = System.currentTimeMillis(); //setting clocktracker
}

/**
  * called when the game starts up (in init())
  */
abstract void setupGame();

/**
  * called every time the screen goes to paint itself
  */
abstract void runGame(Graphics offG);


public void paint(Graphics g) {

	offscreenGraphics.setColor(screenColor);
	offscreenGraphics.fillRect(0,0,screenWidth,screenHeight);  // clear buffer

	runGame(offscreenGraphics);  //game expected to drawitself

	g.drawImage(offscreenImage,0,0,this);
}

/*
 * Utility function for drawing centered text
 */
void centerString(Graphics g, String text, int centerX, int topY){
	int textwidth = g.getFontMetrics().stringWidth(text);
	g.drawString(text,centerX-(textwidth/2),topY);  // clear buffer
}






public void start() {
	animation = new Thread(this);
	if (animation != null) {
		animation.start();
	}
}



// override update so it doesn't erase screen
public void update(Graphics g) {
	paint(g);
}


/*
 * run routine tries to keep applet to certain framerate
 */

public void run() {
	while (true) {
		repaint();
		Thread.currentThread().yield();
		long newTime = System.currentTimeMillis();
//		System.out.println("now:"+newTime+" then:"+oldTime+" diff:"+(newTime-oldTime));
		try {

			//if we're done before the current time dictated
			//by the current framerate, sleep 'til that time
//				Thread.sleep (REFRESH_RATE);
			if(oldTime + REFRESH_RATE > newTime){
				Thread.sleep (oldTime+REFRESH_RATE-newTime);
			} 		
		} catch (Exception exc) { };
		oldTime = newTime;
	}
}



public void stop() {
	if (animation != null) {
		animation.stop();
		animation = null;
	}
}






}