// File: Race8.java (Module 12)
//
// Author: Rahul Simha
// Created: Nov 17, 1998
// Modified: Nov 10, 2000.
//
// Thread groups.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;

class NewFrame extends JFrame {

  // For drawing the race results.
  JPanel drawingArea;

  public NewFrame ()
  {
    // Frame properties.
    this.setTitle ("Dog Race");
    this.setResizable (true);
    this.setSize (600,200);

    Container cPane = this.getContentPane();
    // cPane.setLayout (new BorderLayout());

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

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

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

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

    // Now add the panel to the frame.
    cPane.add (p, BorderLayout.SOUTH);

    // A JPanel to draw the results.
    drawingArea = new JPanel();
    drawingArea.setBackground (Color.white);
    cPane.add (drawingArea, BorderLayout.CENTER);

    this.setVisible (true);
  }


  SafeThreadGroup dogGroup;

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

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

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

    // Create a ThreadGroup instance.
    dogGroup = new SafeThreadGroup ();

    // Create a Thread instance for each dog.
    // Note: the class Dog must implement the
    // Runnable interface.
    Thread dThread1 = new Thread (d1);
    Thread dThread2 = new Thread (d2);

    // Add the threads to the thread group.
    dogGroup.addThread (d1);
    dogGroup.addThread (d2);

    Dog.startRace();

    // Start running the threads.
    // ("start" is a method in Thread).
    dThread1.start();
    dThread2.start();
  }

  public void suspendRace ()
  {
    dogGroup.safeSuspend ();
  }

  public void continueRace ()
  {
    dogGroup.safeResume ();
  }

}


class SafeThreadGroup {

  Vector safeThreads = new Vector();

  public void addThread (SafeRunnable s)
  {
    safeThreads.addElement (s);
  }

  public void safeStop ()
  {
    Enumeration e = safeThreads.elements();
    while (e.hasMoreElements()) {
      SafeRunnable s = (SafeRunnable) e.nextElement();
      s.safeStop();
    }
  }

  public void safeResume ()
  {
    Enumeration e = safeThreads.elements();
    while (e.hasMoreElements()) {
      SafeRunnable s = (SafeRunnable) e.nextElement();
      s.safeResume();
    }
  }
  
  public void safeSuspend ()
  {
    Enumeration e = safeThreads.elements();
    while (e.hasMoreElements()) {
      SafeRunnable s = (SafeRunnable) e.nextElement();
      s.safeSuspend();
    }
  }

}


interface SafeRunnable extends Runnable {

  public abstract void safeStop ();

  public abstract void safeResume ();
  
  public abstract void safeSuspend ();
    
}



class Dog implements SafeRunnable {

  public int position = 20;      // Starting position.
  int ID;                        // An ID.
  JPanel drawingArea;            // The panel on which to draw.

  boolean isAlive = true;        // For safeStop
  boolean isSuspended = false;   // For safeResume/Suspend

  static boolean raceOver;

  public Dog (int ID, JPanel drawingArea)
  {
    this.ID = ID;
    this.drawingArea = drawingArea;

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

  public void move ()
  {
    // Move a random amount.
    int newPosition = position + (int) UniformRandom.uniform (50,100);

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

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

    while ( (isAlive) && (position < finishLine) ) {
	try {
	  Thread.sleep ((int)UniformRandom.uniform (300,600));

          // Check whether suspended.
          checkSuspended();
	}
	catch (InterruptedException e) {
	  System.out.println (e);
	}

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

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

  public static synchronized void startRace ()
  {
    raceOver = false;
  }

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

  public static synchronized boolean raceFinished (boolean set, int ID)
  {
    boolean returnVal = raceOver; 

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

    return returnVal;
  }

  public synchronized void safeStop ()
  {
    isAlive = false;
  }
  
  public synchronized void safeSuspend ()
  {
    isSuspended = true;
  }
  
  public synchronized void safeResume ()
  {
    isSuspended = false;
    this.notify();
  }

  private synchronized void checkSuspended ()
  {
    try {
      while ( (isSuspended) && (isAlive) )
        this.wait();
    }
    catch (InterruptedException e) {
      System.out.println (e);
    }
  }
    
}


public class Race8 {
  public static void main (String[] argv)
  {
    NewFrame nf = new NewFrame ();
  }
}