/*
 *  Copyright 2006 Columbia University.
 *
 *  This file is part of MEAPsoft.
 *
 *  MEAPsoft is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as
 *  published by the Free Software Foundation.
 *
 *  MEAPsoft is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with MEAPsoft; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 *  02110-1301 USA
 *
 *  See the file "COPYING" for the text of the license.
 */

package com.meapsoft;

import java.io.Serializable;
import java.util.Comparator;

/**
 * A way to measure the distance between two chunks.  Constructor can
 * accept another ChunkDist, which will be added to the first
 * distance, so that distance measures can be chained together.
 *
 * @author Mike Mandel (mim@ee.columbia.edu)
 * @author Ron Weiss (ronw@ee.columbia.edu)
 */

public abstract class ChunkDist implements Serializable, Comparator
{
    public Chunk targetChunk = null;
    public ChunkDist next;
    // only compute distance based on these feature dimensions
    public int[] featdim;  
    
    public ChunkDist() 
    { 
        next = null;  
        featdim = null; 
    }

    public ChunkDist(ChunkDist next) 
    {
        this.next = next;
    }

    public ChunkDist(int[] fd) 
    {
        this();
        featdim = fd;
    }

    public ChunkDist(ChunkDist next, int[] fd) 
    {
        this.next = next;
        featdim = fd;
    }

    /**
     * Compute distance between two Chunks
     */
    public double distance(Chunk c1, Chunk c2) 
    {
        if(next != null)
            return next.distance(c1, c2);
        return 0;
    }

    /**
     * Set target chunk for compare function to use.  This needs to be
     * called before compare() is called or there will be
     * NullPointerExceptions.
     */
    public void setTarget(Chunk t)
    {
        targetChunk = t;
    }

    /**
     * Compare two Chunk's based on their distances from targetChunk
     */
    public int compare(Object o1, Object o2) throws ClassCastException
    {
        Chunk c1 = (Chunk)o1;
        Chunk c2 = (Chunk)o2;
        
        // compare distances separate target vector (usually the origin)
        double d1 = distance(c1, targetChunk); 
        double d2 = distance(c2, targetChunk); 

        double comp = d1-d2;
        //System.out.println(d1 + "-" + d2 + " = " + (comp));

        if(comp > 0)
            return 1;
        else if(comp < 0)
            return -1;
        // Fall back to Chunk.compareTo if they are the same
        // distance from target (I don't expect this to happen
        // often...)
        else if(comp == 0)
            return c1.compareTo(c2);

        // this should never happen, but the glorious sun compiler requires it.
        return(0);
    }

    public boolean equals(Object obj)
    {
        return this == obj; 
    }
}