/*
 * Copyright 1996-2002 by Andruid Kerne. All rights reserved.
 * CONFIDENTIAL. Use is subject to license terms.
 */
package ecologylab.collections;
//import java.awt.Toolkit;
import java.util.Iterator;

import ecologylab.generic.Debug;

/**
 * Doubly linked list of GUI components. Maintains family tree.
 */
public class DLL<T>
extends Debug
implements Iterable<T>
{	
   private DLL<T>			prevSib;
   private DLL<T>			nextSib;

   private T				object;

   public DLL(T objectArg)
   {
      object	= objectArg;
   }
/**
 * Add sibs after ourself.
 */
   public synchronized void addAfter(DLL<T> sibs)
   {
      sibs.setNext(nextSib);
      addToEnd(sibs);
   }
   
   /**
    * Insert sibs before ourself.
    */
   public synchronized void insertBefore(DLL<T> sibs)
   {	
  	 sibs.setPrev(prevSib);
  	 if (prevSib != null)
  		 prevSib.setNext(sibs);
  	 sibs.setNext(this);
  	 prevSib = sibs;
   }
/**
 * Add sibs to the end of this.
 * 
 * @param sibs	DLL for object added to the end of this.
 */
   public void addToEnd(DLL<T> sibs)
   {
   		if (sibs == this)
   		{
   			debug("ERROR!!!! adding to end of self!!!!");
   			//Toolkit.getDefaultToolkit().beep();
   			Thread.dumpStack();
   		}
   		
      nextSib	= sibs;		   // ??? should this be setNext(sibs) -- sync
//      setNext(sibs);
      sibs.setPrev(this);
   }
/**
 * Prepend sibs to the start of this.
 * 
 * @param sibs	DLL for object added before this.
 */
   public void addAtBeginning(DLL<T> sibs)
   {
   		if (sibs == this)
   		{
   			debug("ERROR!!!! adding to end of self!!!!");
//   			/Toolkit.getDefaultToolkit().beep();
   			Thread.dumpStack();
   		}
   		
      prevSib	= sibs;		   // ??? should this be setNext(sibs) -- sync
//      setNext(sibs);
      sibs.setNext(this);
   }
/**
 * Remove I and I from the dll of sibs.
 */
   public synchronized void remove()
   {
	   if (nextSib != null)
		   nextSib.setPrev(prevSib);
	   if (prevSib != null)
		   prevSib.setNext(nextSib);
	   prevSib	= null;
	   nextSib	= null;
	   //FIXME -- uncomment this out!
//	   object	= null;		   // encourage gc ?? -- why is this commented out??? andruid 2/10/08
   }
/**
 * Remove the relations of this node, while it is being manipulated in
 * the midst of mergeSort().
 */
   public void clear()
   {
      prevSib	= null;
      nextSib	= null;
//      remove();
      object	= null;
   }
/**
 * Remove the relations of this node, while it is being deleted.
 */
   public void clearStronger()
   {
      remove();
      object	= null;
   }
/**
 * Remove the relations of this node, while it is being rebuilt, and
 * its associations are meaningless.
 */
   public void clearRelations()
   {
      prevSib	= null;
      nextSib	= null;
   }
/**
 * Not usually for public consumption. Only available for special sorts.
 * With a getKey interface, the sort could be brought here, which will
 * be better oo design.
 */
   public synchronized void setNext(DLL<T> next)
   {
      nextSib	= next;
   }
   public synchronized void setPrev(DLL<T> prev)
   {
      prevSib	= prev;
   }
   public T getThis()
   {
      return object;
   }
   public synchronized T getNext()
   {
      return (nextSib == null) ? null : nextSib.object;
   }
   public synchronized T getPrev()
   {
      return (prevSib == null) ? null : prevSib.object;
   }
   public DLL<T> prev()
   {
      return prevSib;
   }
   public DLL<T> next()
   {
      return nextSib;
   }
   public DLL<T> mergeSortDescending(MergeD<T> mergeD, DLL<T> zSibs)
   {
	   DLL<T> c			= this;
	   int n			= 1;
	   DLL<T> head		= new DLL<T>(null);
	   head.setNext(c);
	   DLL<T> a;
	   do 
	   {
		   DLL<T> todo	= head.next();
		   c			= head;
		   int toMove	= n - 1;
//		   System.out.println("");
//		   visualize.CollageElement.printPieces(c.next(), zSibs);
//		   System.out.println("start inner loop moving " + toMove);
		   do
		   {
			   // merge lists of size n
			   DLL<T> t	= todo;
			   a		= t;
			   for (int i=1; i<=toMove; i++)
				   t	= t.next();
			   DLL<T> b	= t.next();
			   t.setNext(zSibs);
			   t		= b;
			   for (int i=1; i<=toMove; i++)
				   t	= t.next();
			   todo	= t.next();
			   t.setNext(zSibs);
//			   System.out.println("mergeDescending(a: ");
//			   visualize.CollageElement.printPieces(a, zSibs);
//			   System.out.println("mergeDescending(b: ");
//			   visualize.CollageElement.printPieces(b, zSibs);
			   c.setNext(mergeD.mergeDescending(a,b));
//			   System.out.println("returns: ");
//			   visualize.CollageElement.printPieces(c.next(), zSibs);
			   int twoN	= n + n;
			   for (int i=1; i<=twoN; i++)
				   c	= c.next();
		   } while (todo != zSibs);
		   n	       += n;
	   } while (a != head.next());

     DLL<T> something = head;
     DLL<T> prev = something;
     while (something != null) {
    	 something = something.next();
    	 if (something == prev)
    		 prev.setNext(null);
    	 prev = something;
     }
       
	   return head.next();
   }

   /**
   * @param object the object to set
   */
   public void setObject(T object)
   {
       this.object = object;
   }
   
   /**
    * Create an {@code Iterator} object for this {@code DLL}. 
    * 
    * @return an {@code Iterator} object for iterating over all elements in this {@code DLL}.
    */
   @Override
public Iterator<T> iterator()
   {
	   return new DLLIterator();
   }
   
   /**
    *  Iterator class for building an iterator object out of the DLL. Uses current 
    *  DLL structure for iteration, starting at the DLL object that instantiates it.
    * 
    */
   private class DLLIterator implements Iterator<T>
   {
	   DLL<T> currentNode = DLL.this;
	   DLL<T> firstObject = DLL.this;
	   boolean stop = false;
	 
	   @Override
	public boolean hasNext()
	   {
		   return !stop && (currentNode != null && currentNode.object != null);
	   }
	
	   @Override
	public T next()
	   {
		   T currentObject 	= currentNode.object;
		   currentNode 		= currentNode.next();
		   if (currentNode == firstObject)
		  	 stop = true;
		   
		   return currentObject;
	   }
		
	   @Override
	public void remove()
	   {
		   // optional method that is not needed in our case. 
	   }
	   
   }
}