// File: Race9.java (Module 12)
//
// Author: Rahul Simha
// Created: Nov 17, 1998
// Modified: Nov 10, 2000.
//
// Waiting and notification.

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

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);

    // 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);
  }


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

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

    // Create the dog monitor.
    DogMonitor monitor = new DogMonitor (2);

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

    // 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);

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


}


// A monitor class with synchronized access.

class DogMonitor {

  // The position of each dog.
  int[] position;

  public DogMonitor (int numDogs)
  {
    position = new int [numDogs+1];
    for (int i=1; i<=numDogs; i++)
      position[i] = 20;
  }

  // Set the new position of Dog# ID.
  public synchronized void setPosition (int ID, int newPosition)
  {
    position[ID] = newPosition;
  }

  // Get the current position of Dog# ID.
  public synchronized int getPosition (int ID)
  {
    return position[ID];
  }

  // A waiting dog needs to call a synchronized
  // wait method inside the monitor.
  public synchronized void synchWait ()
  {
    try {
      // wait() is inherited from Object.
      wait ();
    }
    catch (InterruptedException e)
    {
      System.out.println (e);
    }
  }

  // Tell the other dog that it can continue.
  public synchronized void synchNotify ()
  {
    // notify() is inherited from Object.
    notify ();
  }
}


class Dog implements Runnable {

  int ID;                    // An ID.
  JPanel drawingArea;        // The panel on which to draw.

  DogMonitor monitor;        // Store a reference to the monitor.
  int OtherID;               // ID of the other dog.

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

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

  public void move ()
  {
    // Move a random amount.
    int position = monitor.getPosition (ID);
    int newPosition = position + (int) UniformRandom.uniform (1,50);
    monitor.setPosition (ID, newPosition);

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

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

    // While not complete...
    while (monitor.getPosition (ID) < finishLine) {
      try {
	Thread.sleep ((int)UniformRandom.uniform (300,600));
      }
      catch (InterruptedException e) {
	System.out.println (e);
      }
      
      move ();
      
      // Check if you need to wait.
      int other = monitor.getPosition (OtherID);
      int mine = monitor.getPosition (ID);
      if (mine - other > 20) {
	System.out.println ("ID=" + ID + " waiting: mine=" + mine
			    + ", other=" + other);
	monitor.synchWait ();
	System.out.println ("ID=" + ID + " continuing");
      }
      
      // See if the other guy is waiting for me.
      if (other - mine <= 20) {
	System.out.println ("ID=" + ID + " notifying: mine=" + mine
			    + ", other=" + other);
	monitor.synchNotify();
      }
    } // endwhile

  }

}


public class Race9 {
  public static void main (String[] argv)
  {
    NewFrame nf = new NewFrame ();
  }
}