// Whitaker Brand
// CSE142
// Section BF
// TA: Sarvagya
// 1/22/2018

// This is an example program that we worked on in the A lecture, but not the B lecture.
// It is some more drawing panel practice, and has some cumulative algorithm, and user
// input aspects.
//
// It still could use some improvements:
//  - the inputs from the user are unnatural -- it asks what x displacement and y displacement
//    to use, it would be better to ask for an initial angle, and a displace in whatever direction
//    the ball is travelling.
//  - it doesn't have any method factoring, everything is in main.
//  - size of the ball should probably be a class constant
//  - collision detection with the wall needs some real work. We detect when the ball has collided with
//    the wall, and turn it around after that point, which is a poor model of what would happen in
//    in real life. 
//    -- this is much too complicated for us to solve, though, and would involve making a simple physics
//       engine to answer questions like, how much speed does the ball lose to the collision, how
//       much does the ball compress when it hits the wall, etc.
import java.awt.*;
import java.util.*;

public class Ball {
   public static void main(String[] args) {
      Scanner console = new Scanner(System.in);

      DrawingPanel panel = new DrawingPanel(1000, 1000);
      panel.setBackground(Color.YELLOW);
      Graphics pen = panel.getGraphics();
      
      System.out.print("Please enter the x displacement: ");
      double xDisplacement = console.nextDouble(); // px
      System.out.print("Please enter the y displacement: ");
      double yDisplacement = console.nextDouble();  // px

      // store the x and y locations as a double, because the position of the ball
      // is really continuous, and we don't want to round the location earlier than
      // necessary
      double x = 500.0;
      double y = 500.0;
      
      // but cast the x and y locations to ints for the purposes of drawing, because
      // the Graphics object (pen) can't draw things at double locations.
      pen.fillOval((int) x, (int) y, 20, 20);

      for (int i = 1; i <= 200; i++) {
         // erase where the ball was
         pen.setColor(Color.YELLOW);
         pen.fillOval((int) x, (int) y, 20, 20);
            
         // change the x location of the ball
         // change the y location of the ball
         x = x + xDisplacement;
         y = y + yDisplacement;         
         
         // draw the ball at the new location
         pen.setColor(Color.BLACK);
         pen.fillOval((int) x, (int) y, 20, 20);

         // turn around in th x direction
         if (x + 20 >= 1000 || x <= 0) {
            xDisplacement *= -1;
         }
                  
         if (y <= 0 || y + 20 >= 1000)  {
            yDisplacement *= -1;
	 }

         panel.sleep(100);         
      }      
   }
}