/**
 * @(#)MovingStars.java      1.0.1 98/12/04
 * <p>
 * Copyright (C) 1998 David E. Wexler
 * <p>
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version. See
 * license.txt for a full copy of the GNU GPL.
 * <p>
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * <p>
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
 * USA.
 * <p>
 * To Contact the author send e-mail to vagabond@netdragon.com or send
 * snailmail to: 511 Bobcat Ct, Punta Gorda, FL 3398.
 */

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

/**
 * MovingStars - Displays stars that move at random speeds.
 * <p>
 * This class generates a variable number of stars, puts them at
 * random locations, with random colors, and moves them at random
 * speeds.
 * <p>
 * @author      David Wexler (vagabond@netdragons.com)
 * @version     1.0.1
 * @since       Nelzan1.0.1
 */

class MovingStars {

  private int x[];
  private int y[];
  private int xMove[];
  private int yMove[];
  private Color color[];

  private int height;
  private int width;
  private int maxXMove;
  private int maxYMove;
  private int length;

 /**
  * For generating random Numbers.
  */
  Random r = new Random();
  int i = 0;

 /**
  * Creates All the data to draw MovingStars.
  *
  * @param width        The width of the screen.
  * @param height       The height of the screen.
  * @param maxX         Max speed the stars move in the X direction.
  * @param maxY         Max speed the stars move in the Y direction.
  * @param count        The number of stars to display.
  */
  MovingStars(int width, int height, int maxX, int maxY, int count) {
    this.width = width;
    this.height = height;
    maxXMove = maxX;
    maxYMove = maxY;
    x = new int[count];
    y = new int[count];
    xMove = new int[count];
    yMove = new int[count];
    color = new Color[count];
    length = count-1;
    genStart();
  }

 /**
  * Updates the stars location. It will also generate a new star should the
  * current one be outside of visual range.
  */
  public void update() {
    for (i = 0; i < length; i++) {
      x[i] -= xMove[i];
      if (x[i] < 0) {
        x[i] = width;
        y[i] = abs(r.nextInt()%height);
        color[i] = new Color(abs(r.nextInt()%128)+128, abs(r.nextInt()%128)+128,
         abs(r.nextInt()%128)+128);
      }
      y[i] += yMove[i];
      if (y[i] > height) {
        y[i] = -10;
        x[i] = abs(r.nextInt()%width);
        color[i] = new Color(abs(r.nextInt()%128)+128, abs(r.nextInt()%128)+128,
         abs(r.nextInt()%128)+128);
      }
    }
  }

 /**
  * Paints the stars.
  *
  * @param g            Where to draw the stars.
  */
  public void paint(Graphics g) {
    for (i = 0; i < length; i++) {
      g.setColor(color[i]);
      g.drawLine(x[i],y[i],x[i],y[i]);
    }
  }

 /**
  * Generates the stars starting location, everything is random.
  */
  private void genStart() {
    for (i = 0; i < length; i++) {
      x[i] = abs(r.nextInt()%width);
      y[i] = abs(r.nextInt()%height);
      if (maxXMove == 0)
        xMove[i] = 0;
      else
        xMove[i] = abs(r.nextInt()%maxXMove) + 1;
      if (maxYMove == 0)
        yMove[i] = 0;
      else
        yMove[i] = abs(r.nextInt()%maxYMove) + 1;
      color[i] = new Color(abs(r.nextInt()%128)+128, abs(r.nextInt()%128)+128,
       abs(r.nextInt()%128)+128);
    }
  }

 /**
  * Returns the distance from zero.
  *
  * @param i            The number to check.
  * @returns            an <code>int</code> of the distance from zero.
  */
  private int abs(int i) {
    if (i > 0)
      return i;
    return -i;
  }
}