package edu.calpoly.cpe205.fetter;
import javax.swing.*;
import java.util.*;
import java.io.*;
import java.lang.reflect.*;
import java.lang.*;
import java.awt.*;
import javax.swing.event.*;
import java.awt.event.*;

/** 
 * This class maintains a list of idle ReturnThreads that can be returned to
 * the developer to be used to perform a specific task.
 * @see ReturnThread
 */ 
// Author: Wes Strickland
// Version History
//		Nov 19, 2000 - comments/pseudocode added
//      Nov 30, 2000 - class description changed
//      Feb  8, 2001 - comments added and braces moved for Stage Two release
//      Feb 24, 2001 - (Phillip Hansen) coded freeThread(ReturnThread),
//                     getFreeThread(), ThreadFreeList(), getThreadFreeList()

public class ThreadFreeList
{

	/** 
 	 * This constructor is called once to instantiate only one instance of
 	 * ThreadFreeList
 	 * Pre-conditions:  none
 	 * Post-conditions: one and only instance of ThreadFreeList is constructed
 	 */ 
    private ThreadFreeList()
    {
        // SET freeThreads to NEW collection	//  assigns new collection to freeThreads
        freeThreads = new LinkedList();
    }
    
    /**
     * This method returns the only instance of ThreadFreeList
 	 * Pre-conditions:  none
 	 * Post-conditions: theThreadFreeList is returned
 	 */

    public static ThreadFreeList getThreadFreeList()
    {
        // RETURN theThreadFreeList
        return theThreadFreeList;
    }

    /**
     * Returns a thread that is ready for execution
 	 * Pre-conditions:  none
 	 * Post-conditions: Next thread ready for execution is returned
 	 */
    public ReturnThread getFreeThread()
    {
        ReturnThread freeThread;      // the freeThread to be returned
        
        // CALL isEmpty of collection
        // IF freeThreads is empty THEN 
        //    RETURN new returnThread
        // ELSE 
        //    CALL iterator of freeThreads
        //    CALL next of iterator
        //    CALL remove of iterator with nextitem
        //    RETURN nextitem
                
        /* The following block of code causes a defect because reusing threads doesn't
           seem to work.  You can't call start() on the same thread twice.
        if (freeThreads.isEmpty())
        {
            freeThread = new ReturnThread();
        }
        else
        {
            Iterator itr = freeThreads.iterator();
            freeThread = (ReturnThread)itr.next();
            itr.remove();
        }*/
        
        freeThread = new ReturnThread();
        
        return freeThread;
    }


    /** 
      * Adds a vacationing thread to thelist of FreeThreads
      * Pre-conditions:  none
      * Post-conditions: vacationingThread added to FreeThreads
      * @param vacationingThread a return thread that has completed execution
     */     
    public void freeThread(Thread vacationingThread)
    {
        // CALL add of freeThreads with vacationingThread 
        freeThreads.add(vacationingThread);
    }

    
    private static ThreadFreeList theThreadFreeList = new ThreadFreeList(); //Inner copy of list   

    /**
     *@link aggregation
     *      @associates <{ReturnThread}>
     */
    private java.util.Collection freeThreads;   //Local private copy of collection of free threads
}