package edu.vt.marian.search;

import java.io.*;
import java.util.*;

import edu.vt.marian.common.*;


/**
    A Weighted Object Set with only one element.
    <p> JDK Version  : 1.1.5
	@author	Priyamvadha Lakshminarayanan
	@author	Prajakta Joshi
	@see	WtdObjSet
	@see	edu.vt.marian.common.WtdObj
*/

public class SingletonWtdObjSet implements WtdObjSet
{
	protected Debug debug;

	/** The single element in this set.
	*/
	protected WtdObj onlyElt;

	/**
		A WtdObjSetEnumeration for a SingletonWtdObjSet.
	*/
	public class Enum implements WtdObjSetEnumeration
	{
		boolean eltPassed = false;

		public Enum()
		{
		}

		public synchronized Object nextElement() throws NoSuchElementException
		{
			if ( eltPassed )
				throw(new NoSuchElementException() );
			else
			{
				eltPassed = true;
				return( new WtdObj(onlyElt, debug) );
			}
		}


		public boolean hasMoreElements()
		{
			return( ! eltPassed );
		}


		public synchronized void skip(int k)
		{
			if ( k > 1)
				throw( new NoSuchElementException() );
			if ( k == 1 )
			{
				if ( eltPassed )
					throw( new NoSuchElementException() );
				eltPassed = true;
			}
		}

		public synchronized int sample(int num, WtdObjBag sampleBag)
		{
			int err;
		
			if( eltPassed )
				return( ReturnCodes.OK );
			if (num > 0)
		 	{
				if ((err = sampleBag.add(onlyElt))
					 != ReturnCodes.OK)
					return( err );
		        	eltPassed = true; 
		 	}
			return( ReturnCodes.OK );
		}


		public synchronized int sampleToWt(Weight minWt, WtdObjBag sampleBag)
		{
	    	int err = 0;
		
			if( eltPassed )
				return( ReturnCodes.OK );
		
			if( onlyElt.getWeight().getUnderlyingValue() >= minWt.getUnderlyingValue() )
			{
				if ( (err = sampleBag.add(onlyElt))
					  != ReturnCodes.OK)
					return( err );
				eltPassed = true;
			}
	 		return( ReturnCodes.OK );
		}


		public int exactNumRemaining()
		{
			if ( eltPassed )
				return( 0 );
			else
				return( 1 );
		}

		public int approxNumRemaining()
		{
			if ( eltPassed )
				return( 0 );
			else
				return( 1 );
		}

		public int maxNumRemaining()
		{
			if ( eltPassed )
				return( 0 );
			else
				return( 1 );
		}
	}	// End of SingleWtdObjSet.Enum

	/**
		Construct a singleton set from a single object. 
		@param	w	wtdObj 
		@param	d	Debug
	*/   
	public SingletonWtdObjSet(WtdObj w, Debug d)
	{
		debug = d;
		onlyElt = new WtdObj(w, d);
		// Check the implementation
	}
	
	/**
		Construct a singleton set from a single id and a weight.
		@param	FullID	ID of the only element.
		@param	wt	Weight for the element.
		@param	d	Debug
	*/ 
	public SingletonWtdObjSet(FullID id, Weight wt, Debug d)
	{
		debug = d;
		onlyElt = new WtdObj(id, wt, d);
	}
	
	/**
		Construct a singleton set from details.
		@param	clID	Class Id
		@param	instID	Instance ID
		@param	wt	Weight
	*/
	public SingletonWtdObjSet(int clID, int instID, Weight wt, Debug d)
	{
		debug = d;
		onlyElt = new WtdObj(clID, instID, wt, d);
	}
	

	/**
		Create an Enumeration for this set.
	*/
	public WtdObjSetEnumeration elements()
	{
		return( new Enum() );
	}


	/**
		Is a given ID an Element of this set?
		@param	id	The (ID of the) element to be tested.
		@param	Wt	Set to the Weight of id in this set if id is an element.
		@return	true / false
	*/
	public boolean isElt(FullID id, Weight wt)
	{
	 if (id != onlyElt.getID())
		return( false );

	 wt.set(onlyElt.getWeight());
	 return( true );	
	}

	/**
		Is a given ID an element of this set?	
		@param	id	The (ID of the) element to be tested.
		@return	null -- the element is not in the set.
		<BR>	any valid Weight -- the element is in the set with that Weight.
	*/
	public Weight isElt(FullID id)
	{
	 	if ( id == onlyElt.getID() )
			return( onlyElt.getWeight() );
		else
			return( null );
	}


	/**
		Is this set empty?
		@return	true / false
	*/
	public boolean isEmpty()
	{
	 return( false );	
	}


	/**
		Return the exact number of elements in this set (may be costly).
	*/
	public int exactSize()
	{
		return( 1 );
	}

	/**
		Return the approximate number of elements in this set (can be cheap
			and dirty).
	*/
	public int approxSize()
	{
		return( 1 );
	}

	/**
		Return the maximum number of elements in this set (can be cheap
			and dirty).
	*/
	public int maxSize()
	{
		return( 1 );
	}


	/**
		Return a human-readable string for this entire set (may be large).
	*/
	public String toString()
	{
		return( new String("{" + onlyElt.toString() + "}") );
	}

	/**
		Return a short human-readable string that quickly describes this set.
	*/
	public String profile()
	{
		return( new String("{" + onlyElt.toString() + "}") );
	}

}	// End of SingletonWtdObjSet.