import java.awt.*;     // Needed for window and graphics (explained in COMP1406)
import javax.swing.*;  // Needed for window and graphics (explained in COMP1406)

// This application simulates balls bouncing in a window
public class BallSimulation {
    // This variable stores the panel that displays the balls
    // (This is a topic discussed in COMP1406 course)
    public static BallPanel   ballPanel;
    
    public static void startSimulation(Ball[] balls) {
        while(true) {
            for (int i=0; i<balls.length; i++) {
                // move the ball forward
                balls[i].x = balls[i].x + (int)(balls[i].speed*Math.cos(balls[i].direction)); 
                balls[i].y = balls[i].y + (int)(balls[i].speed*Math.sin(balls[i].direction));
                
                // check if ball collides with borders and adjust accordingly
                if ((balls[i].x + balls[i].radius >= BallPanel.WIDTH) || (balls[i].x - balls[i].radius <= 0))
                    balls[i].direction = (float)(Math.PI - balls[i].direction);
                if ((balls[i].y + balls[i].radius >= BallPanel.HEIGHT) || (balls[i].y - balls[i].radius <= 0))
                    balls[i].direction = -balls[i].direction;
            }
            ballPanel.repaint();
            try{ Thread.sleep(10); } catch(Exception e){};
        }
    }

    // Create a window with a BallPanel, add 3 balls and start the simulation
    public static void main(String args[]) {
        Ball[]   balls = new Ball[3];
        balls[0] = new Ball();
        balls[0].x = 100;
        balls[0].y = 100;
        balls[0].direction = (float)(Math.random()*2*Math.PI);
        balls[0].speed = 15;
        balls[0].radius = 20;
        
        balls[1] = new Ball();
        balls[1].x = 400;
        balls[1].y = 300;
        balls[1].direction = (float)(Math.random()*2*Math.PI);
        balls[1].speed = 10;
        balls[1].radius = 30;
        
        balls[2] = new Ball();
        balls[2].x = 600;
        balls[2].y = 400;
        balls[2].direction = (float)(Math.random()*2*Math.PI);
        balls[2].speed = 5;
        balls[2].radius = 50;
        
        JFrame frame = new JFrame("Ball Simulation");
        frame.add(ballPanel = new BallPanel(balls));
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack(); // Makes size according to panel's preference
        frame.setVisible(true);
        
        startSimulation(balls);
    }
}