// Helene Martin, CSE 142
// Animates two falling balls affected by gravity.

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

public class BallSimulation {
	public static final int PANEL_SIZE = 400;
	public static final int BALL_SIZE = 40;
	public static final double GRAVITY_ACC = 9.81;	// m / sec^2
	public static final double TIME_STEP = 0.1;		// secs
	
	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		
		// Note: the following 5 line are redundant.
		// We can only return one thing from a method and they get 3 values.
		// For now, we can't reduce this redundancy.
		System.out.print("Ball 1 starting x y: ");		
		int ball1x = s.nextInt();
		int ball1y = s.nextInt();
		System.out.print("Ball 1 starting velocity: ");
		double ball1V0 = s.nextDouble();
		
		System.out.print("Ball 2 starting x y: ");		
		int ball2x = s.nextInt();
		int ball2y = s.nextInt();
		System.out.print("Ball 2 starting velocity: ");		
		double ball2V0 = s.nextDouble();
		
		DrawingPanel panel = new DrawingPanel(PANEL_SIZE, PANEL_SIZE);
		Graphics g = panel.getGraphics();
		
		for(double t = 1; t <= 10; t += TIME_STEP) {
			double ball1Disp = displacement(ball1V0, GRAVITY_ACC, t);
			g.setColor(Color.RED);
			g.fillOval(ball1x, (int)(ball1y + ball1Disp), BALL_SIZE, BALL_SIZE);
			
			double ball2Disp = displacement(ball2V0, GRAVITY_ACC, t);
			g.setColor(Color.BLUE);
			g.fillOval(ball2x, (int)(ball2y + ball2Disp), BALL_SIZE, BALL_SIZE);		
			
			panel.sleep((int)(1000 * TIME_STEP));
			panel.clear();
		}
	}
	
	// Calculates the displacement of an objects starting at velocity v0
	// after t seconds have passed, given an acceleration of a.
	public static double displacement(double v0, double a, double t) {
		return v0 * t + (a / 2) * Math.pow(t, 2);
	}

}