import java.awt.*;
import rebelsky.io.SimpleGUI;

/**
 * Draw a set of movable concentric circles on the screen.
 * <p>
 * Copyright (c) 1998 Samuel A. Rebelsky.  All rights reserved.
 *
 * @author Samuel A. Rebelsky
 * @version 1.1 of February 1998
 */
public class Circles extends SimpleGUI
{
  /*
   * Implementation notes:  We'll keep track of the center of the
   * circles and the radius of the innermost circle.  When the
   * user presses a specified key, we'll change the radius or center.
   */

  // +-----------+---------------------------------------------------------
  // | Constants |
  // +-----------+

  /**
   * The base change in diameter when the user shrinks or enlarges 
   * the circle.  In actuality, the circle may change by more, as we
   * work with circles with different diameters.
   */
  protected static int DELTA_SIZE = 1;
  
  /**
   * The change in X or Y position.  An appropriate number was determined
   * by experimentation.
   */
  protected static int DELTA_POS = 3;


  // +--------+------------------------------------------------------------
  // | Fields |
  // +--------+

  /**
   * The basic radius of circles.
   */
  protected int radius;

  /**
   * The x position (distance from left margin) of the center of
   * the circles.
   */
  protected int x;

  /**
   * The y position (distance from top margin) of the center of the
   * the circles.
   */
  protected int y;


  // +--------------+------------------------------------------------------
  // | Constructors |
  // +--------------+

  /**
   * Start with the circle of radius 10, centered at (100,100).
   */
  public Circles()
  {
    radius = 10;
    x = 100;
    y = 100;
  } // Circles


  // +---------+-----------------------------------------------------------
  // | Methods |
  // +---------+

  /**
   * Handle key presses using the numeric keypad to govern changes.
   * 4 is left, 8 is up, and so on and so forth.  Instructions are
   * given to the user in the title.
   */
  public void handleKey(char key)
  {
    switch (key)
    {
      case '0':			// Enlarge
        radius = radius + DELTA_SIZE;
        break;
      case '2':			// Down
        y = y + DELTA_POS; 
        break;
      case '4':			// Left
        x = x - DELTA_POS; 
        break;
      case '5':			// Reduce
        radius = radius - DELTA_SIZE;
        break;
      case '6':			// Right
        x = x + DELTA_POS; 
        break;
      case '8':			// Up
        y = y - DELTA_POS; 
        break;
      default:
        super.handleKey(key);
        break;
    } // switch
  } // handleKey

  /**
   * Paint the circles on the screen.
   */
  public void paintStuff(Graphics g)
  {
    // Outermost circle: red, 3*base size
    g.setColor(Color.red);
    g.drawOval(x-radius*3, y-radius*3, radius*6, radius*6);
    // Next circle: blue, 2*base size
    g.setColor(Color.blue);
    g.drawOval(x-radius*2, y-radius*2, radius*4, radius*4);
    // Next circle: green, 1*base size
    g.setColor(Color.green);
    g.drawOval(x-radius*1, y-radius*1, radius*2, radius*2);
  } // paintStuff(Graphics)


  // +------+--------------------------------------------------------------
  // | Main |
  // +------+

  /**
   * Set the title and then start running the GUI.
   */
  public static void main(String[] args)
  {
    Circles gui = new Circles();
    gui.setTitle("Circles");
    gui.setCaption("4-left; 2-down; 8-up; 6-right; 5-shrink; 0-enlarge; q-quit");
    gui.run();
  } // main(String[])

} // Circles