package edu.vt.marian.search;

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

import edu.vt.marian.common.*;


/**
    A Vector-based cache for any WtdObjSet or WtdObjSet-like object.
    @author	Robert France
    <p> JDK Version  : 1.1.5
	@see	WtdObjSet
	@see	VectorWtdObjSetEnum
*/


public class VectorWtdObjSet implements WtdObjSet
{
	protected Debug debug;		// The eternal Debug object.

	protected Vector v;	// Used to store WtdObjs, and only WtdObjs.


	public class Enum implements WtdObjSetEnumeration
	{
		protected int nextElt;

		public Enum()
		{
			nextElt = 0;
		}


		public synchronized Object nextElement()
		{
			if ( nextElt >= v.size() )
				throw( new NoSuchElementException() );
			return( v.elementAt(nextElt++) );
		}


		public boolean hasMoreElements()
		{
			return( nextElt < v.size() );
		}

		
		/**
			Skip forward a certain number of elements.
			@param	k	How many elements to skip.
			@exception	NoSuchElementException
		*/
		public synchronized void skip(int k)
		{
			if ( nextElt+k >= v.size() )
				throw( new NoSuchElementException() );
			nextElt += k;
		}


		/**
			Copy a certain number of elements into a bag.
			@param	num	How many elements to copy.
			@param	sampleBag	The WtdObjBag to add elements to.
			@return	OK	There were Num elements left, and they all were copied well.
			<BR>	anything else	Problems.
			@exception	NoSuchElementException
		*/
  		public synchronized int sample(int num, WtdObjBag sampleBag)
		{
			int i;
			WtdObj w;
			int err;
			for (i=0; i<num; i++)
			{
				if (nextElt >= v.size() )
					break;
				w = (WtdObj) v.elementAt(nextElt++);
				if ( (err = sampleBag.add(w)) != ReturnCodes.OK)
					return( err );
			}
			return( ReturnCodes.OK );
		}

	
		/**
			Copy into a bag all the members of this set with weights >= some weight.
			@param	minWt	The lowest weight to copy.
			@param	sampleBag	The WtdObjBag to add elements to.
			@return	OK	There were Num elements left, and they all were copied well.
			<BR>	anything else	Problems.
			@exception	NoSuchElementException
		*/
	  	public synchronized int sampleToWt(Weight minWt, WtdObjBag sampleBag)
		{
			WtdObj w;
			int err;
			while (true)
			{
				if ( nextElt >= v.size() )
					break;
				w = (WtdObj) v.elementAt(nextElt);
				if ( minWt.compare(w.getWeight()) == Weight.HIGHER )
					break;
				nextElt++;
				if ( (err = sampleBag.add(w)) != ReturnCodes.OK)
					return( err );
			} 
			return( ReturnCodes.OK );
		}


		/**
			Return exact number of elements remaining in the parent set.
			@return	The exact number of elements still to be enumerated.
		*/      
		public int exactNumRemaining()
		{
			return( v.size() - nextElt );
		}


		/**
			Return approximate number of elements left.
			@return	The approximate number of elements still to be enumerated.
		*/      
		public int approxNumRemaining()
		{
			return( v.size() - nextElt );
		}

		/**
			Return maximum number of elements left.
			@return	The maximum number of elements still to be enumerated.
		*/
		public int maxNumRemaining()
		{
			return( v.size() - nextElt );
		}
	}


	public VectorWtdObjSet(Debug d)
	{
		debug = d;
		v = new Vector();
	}

	public VectorWtdObjSet(int expectedSize, Debug d)
	{
		debug = d;
		v = new Vector(expectedSize);
	}


	public int add(WtdObj w)
	{
		try
		{
			WtdObj lastElt = (WtdObj) v.lastElement();
			if ( w.compare(lastElt) == Weight.LOWER )
			{
				int i;
				for (i=0; i<v.size(); i++)
				{
					lastElt = (WtdObj) v.elementAt(i);
					if ( w.compare(lastElt) != Weight.LOWER )
					{
						v.insertElementAt(w, i);
						break;
					}
				}
			}
			else
			{
				v.addElement(w);
			}
		} catch( NoSuchElementException e )
		   {
			v.addElement(w);
		   }
		return( ReturnCodes.OK );
	}	// end VectorWtdObjSet.Enum


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

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


	/**
		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.
		<P>
		<B>NOTE:</B>  We cannot use Vector.contains() (or even indexOf()) here
			because Vectors compare objects by identity, not equality.
	*/
	public Weight isElt(FullID id)
	{
		Enumeration elts = v.elements();
		try
		{
			while( true )
			{
				WtdObj w = (WtdObj) elts.nextElement();
				if ( id.equals(w) )
					return( w.getWeight() );
			}
		} catch( NoSuchElementException e )
		   {
			return( Weight.bottomWt );
		   }
	}


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

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

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


	/**
		Return a human-readable string for this entire set (may be large).
	*/
	public String toString()
	{
		StringBuffer sb = new StringBuffer(v.size()*30 + 2);
		sb.append('{');
		Enumeration elts = v.elements();
		try
		{
			WtdObj w = (WtdObj) elts.nextElement();
			sb.append(w.toString());
			while( true )
			{
				w = (WtdObj) elts.nextElement();
				sb.append(',');
				sb.append(w.toString());
			}
		} catch( NoSuchElementException e ) { }
		sb.append('}');
		return( sb.toString() );
	}

	/**
		Return a short human-readable string that quickly describes this set.
	*/
	public String profile()
	{
		StringBuffer sb = new StringBuffer(100);
		sb.append('{');
		if ( v.size() > 0 )
		{
			WtdObj w = (WtdObj) v.firstElement();
			sb.append(w.toString());
			if ( v.size() > 1 )
			{
				w = (WtdObj) v.elementAt(1);
				sb.append(',');
				sb.append(w.toString());
				if ( v.size() > 2 )
				{
					sb.append(',');
					if ( v.size() > 3 )
					{
						sb.append("...[" + (v.size()-3) + "]...,");
					}
					w = (WtdObj) v.lastElement();
					sb.append(w.toString());
				}
			}
		}
		sb.append('}');
		return( sb.toString() );
	}
};