// File: Store.java
// T Balls : Nov 2001
// Implement a thread safe integer store for the PutGet problem

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

/**
 *  Create and maintain storage for a single integer.
 * Protect access to the store using synchronised put and get methods
 */
public class Store extends JPanel
{
   /**
      *   Default constructor.
      *
      *   Create the visual components of the store display
      *    - a scrolling log area and the current contents of the store
      */
   public Store()
   {
      setLayout( new BorderLayout() );
      value = 0;
      displayValue = new JLabel( "[ " + value + " ]", JLabel.CENTER );
      displayValue.setOpaque( true );
      displayValue.setBackground( Color.white );
      displayValue.setForeground( Color.red );
      displayValue.setFont( new Font( "SansSerif", Font.BOLD, 22 ) );
      add( displayValue, BorderLayout.SOUTH );
      log = new Log( 30, 20 );
      add( log, BorderLayout.CENTER );
   }

   private int value;
   private JLabel displayValue;
   private Log log;

   /**
      *   Put a value into the store.
      *
      *   Thread-protected method to put a value into the store
      *   The calling thread is made to wait if the store is full (!=0)
      *   The name of the thread is used to identify actions to the on-screen log
      */
   public synchronized void put( int valueToPut )
   {
      log.append( "" + Thread.currentThread().getName() +" to put " + valueToPut );
      while( value != 0 )
      {
         log.append( " - waiting\n" );
         try
         {
            wait();
         }
         catch( InterruptedException ie )
         {}
         log.append( "" + Thread.currentThread().getName() +" woken up" );
      }
      log.append( "\n" );
      value = valueToPut;
      displayValue.setText( "[ " + value + " ]" );
      notifyAll();
   }

   /**
      *   Get a value from the store.
      *
      *   Thread-protected method to retrieve a value from the store
      *   The calling thread is made to wait if the store is empty (==0)
      *   The name of the thread is used to identify actions to the on-screen log
      */
   public synchronized int get()
   {
      log.append( "" + Thread.currentThread().getName() +" to get value" );
      while( value == 0 )
      {
         log.append( " - waiting\n" );
         try
         {
            wait();
         }
         catch( InterruptedException ie )
         {}
         log.append( "" + Thread.currentThread().getName() +" woken up" );
      }
      log.append( "\n" );
      int valueToReturn = value;
      value = 0;
      displayValue.setText( "[ " + value + " ]" );
      notifyAll();
      return valueToReturn;
   }

}