// File: IO24.java (Module 13)
//
// Author: Rahul Simha
// Created: Nov 30, 1998
//
// Using start() and stop()


import java.awt.*;
import java.awt.event.*;
import java.applet.*;

public class IO24 extends Applet {

  Canvas c;

  public void init ()
  {
    // Frame properties.
    this.setBackground (Color.cyan);

    // Must set layout of the panel.
    this.setLayout (new BorderLayout());

    // Quit button.
    Panel p = new Panel ();
    Button quitb = new Button ("QUIT");
    quitb.addActionListener (
      new ActionListener () {
        public void actionPerformed (ActionEvent a)
        {
	  System.exit (0);
	}
      }
    );
    p.add (quitb);

    // Pressing "start" calls race()
    Button startb = new Button ("START");
    startb.addActionListener (
      new ActionListener () {
        public void actionPerformed (ActionEvent a)
        {
	  race ();
	}
      }
    );
    p.add (startb);

    Button pauseb = new Button ("PAUSE");
    pauseb.addActionListener (
      new ActionListener () {
        public void actionPerformed (ActionEvent a)
        {
	  suspend_race ();
	}
      }
    );
    p.add (pauseb);

    Button continueb = new Button ("CONTINUE");
    continueb.addActionListener (
      new ActionListener () {
        public void actionPerformed (ActionEvent a)
        {
	  continue_race ();
	}
      }
    );
    p.add (continueb);

    this.add (p, BorderLayout.SOUTH);

    // A canvas to draw the results.
    c = new Canvas();
    c.setBackground (Color.white);
    this.add (c, BorderLayout.CENTER);

    // Create a ThreadGroup instance.
    DogGroup = new ThreadGroup ("All dogs");

    this.setVisible (true);
  }


  ThreadGroup DogGroup;

  void race ()
  {
    Dimension D = c.getSize ();

    // Finish-line is at the right end of the canvas.
    int finish_line = D.width;

    // Create two dog instances with different ID's.
    Dog d1 = new Dog (1, c);
    Dog d2 = new Dog (2, c);

    // Create a Thread instance for each dog.
    // Note: the class Dog must implement the
    // Runnable interface.
    Thread d1_thread = new Thread (DogGroup, d1);
    Thread d2_thread = new Thread (DogGroup, d2);

    Dog.start_race();

    // Start running the threads.
    // ("start" is a method in Thread).
    d1_thread.start();
    d2_thread.start();
  }

  public void suspend_race ()
  {
    DogGroup.suspend ();
  }

  public void continue_race ()
  {
    DogGroup.resume ();
  }

  public void stop ()
  {
    DogGroup.suspend ();
  }

  public void start ()
  {
    DogGroup.resume ();
  }

}


class Dog implements Runnable {

  public int position = 20;  // Starting position.
  int ID;                    // An ID.
  Canvas c;                  // The canvas on which to draw.

  static boolean race_over;

  public Dog (int ID, Canvas c)
  {
    this.ID = ID;
    this.c = c;

    // Draw ID on canvas.
    Graphics g = c.getGraphics ();
    g.drawString (""+ID, 5, 20*ID+8);
  }

  public void move ()
  {
    // Move a random amount.
    int new_position = position + (int) UniformRandom.uniform (20,30);

    // Draw new position.
    Graphics g = c.getGraphics ();
    int size = new_position - position;
    g.fillRect (position, 20*ID, size, 10);
    position = new_position;
  }

  public void run ()
  {
    // Compute the finish line distance.
    int finish_line = c.getSize().width;

    // While not complete...
    while (position < finish_line) {
	try {
	  Thread.sleep ((int)UniformRandom.uniform (300,600));
	}
	catch (InterruptedException e) {
	  System.out.println (e);
	}

	// Check whether race is over.
	if (race_finished (false, ID)) break;

	// Move if race is still on.
	move ();
    }
    if (position >= finish_line)
      race_finished (true, ID);
  }

  public static synchronized void start_race ()
  {
    race_over = false;
  }

  // The same method is called to check whether the race
  // is complete or to indicate that it is complete.

  public static synchronized boolean race_finished (boolean set, int ID)
  {
    boolean return_val = race_over; 

    if (!set) 
      return_val = race_over;
    else {
      // Race overseer sleeps for a while.
      try {
	Thread.sleep ((int)UniformRandom.uniform (1000,2000));
      }
      catch (InterruptedException e) {
	System.out.println (e);
      }
      race_over = true;
      return_val = true;
    }

    return return_val;
  }

}