/*
  * File: Ball.java
  * Author: Java, Java, Java
  * Description: This class defines a ball that bounces back and forth
  *  and up and down within an applet. The "bouncing" is effected by
  *  repeatedly drawing, erasing and moving the ball in the run() method.
  *  Note the use of class constants in the program and the use of
  *  XOR mode in the draw method.
  *
  * This version of Ball also keeps track of the location of the paddle.
  * The applet is used to mediate the connection between the paddle and the
  * ball. Whenever the ball hits the paddle, it bounces at a random angle.
  */

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

public class Ball extends Thread {
     public static final int SIZE = 10;   // Diameter of the ball
     private PongApplet applet;           // Reference to the applet
     private int topWall, bottomWall, leftWall, rightWall;  // Boundaries
     private int locationX, locationY;     // Current location of the ball
     private int directionX = 1, directionY = 1; //x- and y-direction (1 or -1)
     private Toolkit kit = Toolkit.getDefaultToolkit(); //For beep() method

     /**
      * Ball() constructor sets a pointer to the applet and initializes
      *  the ball's location at the center of the bouncing region
      */
     public Ball(PongApplet app) {
         applet = app;
         locationX = leftWall + 1;                // Set initial location
         locationY = bottomWall/2;
     } // Ball()

     /**
      * Return the x coordinate of the ball's location
      */
     public int getX() {
         return locationX;
     }

     /**
      * Return the x coordinate of the ball's location
      */
     public int getY() {
         return locationY;
     }

     /**
      * move() changes the ball's vertical location (y-coordinate) by DY pixels.
      *  It then checks if the ball has reached a boundary and if so 
      *  reverses direction
      */
      public void move() {
          rightWall = applet.getWidth() - SIZE;   // Define bouncing region
          leftWall = topWall = 0;                 // And location of walls
          bottomWall = applet.getHeight() - SIZE;

          locationX = locationX + directionX; // Calculate a new location
          locationY = locationY + directionY;

          if (applet.ballHitsPaddle()){
              directionX = -1;   //  move toward left wall
              kit.beep();
          } //if ball hits paddle
          if (locationX <= leftWall){
              directionX = + 1;   //  move toward right wall
              kit.beep();
          } //if ball hits left wall
          if (locationY + SIZE >= bottomWall || locationY <= topWall){
              directionY = -directionY;      //  reverse direction
              kit.beep();
          } //if ball hits top or bottom walls
          if (locationX  >= rightWall + SIZE) {
              locationX = leftWall + 1;   // jump back to left wall
          } //if ball goes through right wall
      } // move()

      /**
      * run() repeatedly draws, erases and moves the ball
      */
      public void run() {
          while (true) {
              move();                // Move
              applet.repaint();
              try {  sleep(15);
              } catch (InterruptedException e) {}
         } // while
      } // run()
} // Ball