/*
 * $Id$
 */

package edu.jas.gb;


import edu.jas.poly.GenWordPolynomial;
import edu.jas.structure.RingElem;


/**
 * Serializable subclass to hold pairs of word polynomials.
 * @param <C> coefficient type
 * @author Heinz Kredel
 */
public class WordPair<C extends RingElem<C>> implements Comparable<WordPair> {


    public final GenWordPolynomial<C> pi;


    public final GenWordPolynomial<C> pj;


    public final int i;


    public final int j;


    protected int n;


    /**
     * WordPair constructor.
     * @param a word polynomial i.
     * @param b word polynomial j.
     * @param i first index.
     * @param j second index.
     */
    public WordPair(GenWordPolynomial<C> a, GenWordPolynomial<C> b, int i, int j) {
        pi = a;
        pj = b;
        this.i = i;
        this.j = j;
        this.n = 0;
    }


    /**
     * toString.
     */
    @Override
    public String toString() {
        return "wordPair(" + i + "," + j + ",{" + pi.length() + "," + pj.length() + "}," + n + ")";
    }


    /**
     * Set removed pair number.
     * @param n number of this pair generated in OrderedPairlist.
     */
    public void pairNumber(int n) {
        this.n = n;
    }


    /**
     * Get removed pair number.
     * @return n number of this pair generated in OrderedPairlist.
     */
    public int getPairNumber() {
        return n;
    }


    /**
     * equals.
     * @param ob an Object.
     * @return true if this is equal to o, else false.
     */
    @Override
    public boolean equals(Object ob) {
        if (!(ob instanceof WordPair)) {
            return false;
            // throw new ClassCastException("Pair "+n+" o "+o);
        }
        return 0 == compareTo((WordPair) ob);
    }


    /**
     * compareTo used in TreeMap // not used at moment. Comparison is based on
     * the number of the pairs.
     * @param p a WordPair.
     * @return 1 if (this &lt; o), 0 if (this == o), -1 if (this &gt; o).
     */
    public int compareTo(WordPair p) {
        int x = p.getPairNumber();
        if (n > x) {
            return 1;
        }
        if (n < x) {
            return -1;
        }
        return 0;
    }


    /**
     * Hash code for this WordPair.
     * @see java.lang.Object#hashCode()
     */
    @Override
    public int hashCode() {
        return (i << 16) + j;
    }

}
