// Helene Martin, CSE 142
// Simulates two balls with initial y velocity falling due to gravity.

// goal: show complex drawing panel program and demonstrate 
// user input with Scanner
import java.awt.*;
import java.util.*;

public class BallSimulation {
	public static final double ACC_GRAVITY = 9.81; // pixels/s^2
	public static final int BALL_DIAMETER = 70;
	public static final double TIME_STEP = .1; // s
	
	public static void main(String[] args) {
		Scanner console = new Scanner(System.in);
		
		// Note: the two blocks of code that follow are redundant.
		// They each capture 3 pieces of information, though, and
		// we can only return 1 thing from a method!  So for now we 
		// live with it.		
		System.out.print("Give me the x and y coordinate of ball 1: ");			
		int ball1x = console.nextInt();
		int ball1y = console.nextInt();
		System.out.print("Give me an initial velocity for ball 1: ");
		double ball1V0 = console.nextDouble();
		
		System.out.print("Give me the x and y coordinate of ball 2: ");			
		int ball2x = console.nextInt();
		int ball2y = console.nextInt();
		System.out.print("Give me an initial velocity for ball 2: ");
		double ball2V0 = console.nextDouble();
		
		// Create the DrawingPanel later so it doesn't pop up
		DrawingPanel panel = new DrawingPanel(400, 400);
		Graphics g = panel.getGraphics();

		// calculate position and draw balls at each time step
		for (double t = 0; t < 10; t += TIME_STEP) {
			g.setColor(Color.RED);
			double disp1 = displacement(ball1V0, t, ACC_GRAVITY);
			g.fillOval(ball1x, ball1y + (int)disp1, BALL_DIAMETER, BALL_DIAMETER);
	
			g.setColor(Color.BLUE);
			double disp2 = displacement(ball2V0, t, ACC_GRAVITY);
			g.fillOval(ball2x, ball2y + (int)disp2, BALL_DIAMETER, BALL_DIAMETER);
			
			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 t, double a) {
		return v0 * t + (a * Math.pow(t, 2)) / 2;
	}
}