package edu.vt.marian.search;

import java.io.*;
import java.net.*;
import java.lang.*;
import java.util.*;

import edu.vt.marian.common.*;

/**
 * This class augments weighted objects with a "pointer" to a FullID.
 * This is to enable the creation of weighted object tables which are
 * "threaded" like a singly-linked list.  The purpose of such a table
 * is to allow O(1) ("direct") access to any point in the logical
 * list, but thereafter to "follow" the entries in the list from that
 * point onwards.
 * 
 * @author Paul Mather
 * @version 0.9
 * @see edu.vt.marian.common.WtdObj
 * @see edu.vt.marian.common.FullID
 * @see edu.vt.marian.common.Debug
 */
public class WtdObjSingleLink extends WtdObj
{
    /** "Pointer" to the next "list" entry */
    protected FullID next;

    /**
     * Create a singly-linked weighted object given only a debug
     * object.  The resultant object will have its weighted object set
     * to a newly-created WtdObj and its next "pointer" set to a
     * newly-created---and invalid---FullID.
     * @param debug debug object
     */
    public WtdObjSingleLink( Debug debug )
    {
	super(debug);
	this.next = null;
    }

    /**
     * Create a singly-linked weighted object given a weighted object
     * (and a debug object).  The resultant object will have its next
     * "pointer" set to a newly-created---and invalid---FullID.
     * @param w     weighted object
     * @param debug debug object
     */
    public WtdObjSingleLink( WtdObj w, Debug debug )
    {
	super(w, debug);
	this.next = null;
    }

    /**
     * Create a singly-linked weighted object given a weighted object,
     * a FullID pointing to the "next" list item, and a debug object.
     * @param w     weighted object
     * @param next  key of next element in this list
     * @param debug debug object
     */
    public WtdObjSingleLink( WtdObj w, FullID fullID, Debug debug )
    {
	super(w, debug);
	this.next = new FullID(fullID, debug);
    }

    /**
     * Return the FullID key of the next item pointed to in this ordering.
     * @return key of the next weighted object in this ordering
     */
    public FullID getNext()
    {
	return this.next;
    }

    /**
     * Set the FullID key of the next item pointed to in this ordering.
     * @param nextElt the "key" of the next element "pointed" to by this one
     * @return key of the next weighted object in this ordering
     */
    public void setNext(FullID nextElt)
    {
//  	if (nextElt.isValid())
	    this.next = nextElt;
//  	else
//  	{
//  	    debug.dumpTrace("WtdObjSingleLink.setNext: Invalid FullID");
//  	    this.next = null;
//  	}
    }

    /**
     * Return the WtdObj portion of this WtdObjSingleLink object.
     * @return copy of the WtdObj portion of this WtdObjSingleLink object.
     */
    public WtdObj getWtdObj()
    {
	return new WtdObj(this.getID(),this.getWeight(),this.debug);
    }

    /**
     * Convert this WtdObjSingleLink to a string representation.
     * The printable form is "WtdObj(FullID)", where WtdObj
     * is the string representation of the weighted object portion
     * of this object, and FullID is the string representation of
     * the FullID "next" pointer of this object.
     * @return string containing printable representation of object data
     * @see edu.vt.marian.common.WtdObj#toString
     * @see edu.vt.marian.common.FullID#toString
     */
    public String toString()
    {
	if (next == null)
	    return super.toString() + "(null)" ;
	else
	    return super.toString() + '(' + next.toString() + ')';
    }
}