/*
 * $Id$
 */

package edu.jas.gb;


import java.io.Serializable;
import java.util.List;

import edu.jas.poly.ExpVector;
import edu.jas.poly.GenPolynomial;
import edu.jas.structure.RingElem;


/**
 * Polynomial Reduction interface. Defines S-Polynomial, normalform, criterion
 * 4, module criterion and irreducible set.
 * @param <C> coefficient type
 * @author Heinz Kredel
 */

public interface Reduction<C extends RingElem<C>> extends Serializable {


    /**
     * S-Polynomial.
     * @param Ap polynomial.
     * @param Bp polynomial.
     * @return spol(Ap,Bp) the S-polynomial of Ap and Bp.
     */
    public GenPolynomial<C> SPolynomial(GenPolynomial<C> Ap, GenPolynomial<C> Bp);


    /**
     * S-Polynomial with recording.
     * @param S recording matrix, is modified.
     * @param i index of Ap in basis list.
     * @param Ap a polynomial.
     * @param j index of Bp in basis list.
     * @param Bp a polynomial.
     * @return Spol(Ap, Bp), the S-Polynomial for Ap and Bp.
     */
    public GenPolynomial<C> SPolynomial(List<GenPolynomial<C>> S, int i, GenPolynomial<C> Ap, int j,
                    GenPolynomial<C> Bp);


    /**
     * Module criterium.
     * @param modv number of module variables.
     * @param A polynomial.
     * @param B polynomial.
     * @return true if the module S-polynomial(i,j) is required.
     */
    public boolean moduleCriterion(int modv, GenPolynomial<C> A, GenPolynomial<C> B);


    /**
     * Module criterium.
     * @param modv number of module variables.
     * @param ei ExpVector.
     * @param ej ExpVector.
     * @return true if the module S-polynomial(i,j) is required.
     */
    public boolean moduleCriterion(int modv, ExpVector ei, ExpVector ej);


    /**
     * GB criterium 4. Use only for commutative polynomial rings.
     * @param A polynomial.
     * @param B polynomial.
     * @param e = lcm(ht(A),ht(B))
     * @return true if the S-polynomial(i,j) is required, else false.
     */
    public boolean criterion4(GenPolynomial<C> A, GenPolynomial<C> B, ExpVector e);


    /**
     * GB criterium 4. Use only for commutative polynomial rings.
     * @param A polynomial.
     * @param B polynomial.
     * @return true if the S-polynomial(i,j) is required, else false.
     */
    public boolean criterion4(GenPolynomial<C> A, GenPolynomial<C> B);


    /**
     * GB criterium 4.
     * @param ei exponent vector.
     * @param ej exponent vector.
     * @param e = lcm(ei,ej)
     * @return true if the S-polynomial(i,j) is required, else false.
     */
    public boolean criterion4(ExpVector ei, ExpVector ej, ExpVector e);


    /**
     * Is top reducible. Condition is lt(B) | lt(A) for some B in F.
     * @param A polynomial.
     * @param P polynomial list.
     * @return true if A is top reducible with respect to P.
     */
    public boolean isTopReducible(List<GenPolynomial<C>> P, GenPolynomial<C> A);


    /**
     * Is reducible.
     * @param A polynomial.
     * @param P polynomial list.
     * @return true if A is reducible with respect to P.
     */
    public boolean isReducible(List<GenPolynomial<C>> P, GenPolynomial<C> A);


    /**
     * Is in Normalform.
     * @param A polynomial.
     * @param P polynomial list.
     * @return true if A is in normalform with respect to P.
     */
    public boolean isNormalform(List<GenPolynomial<C>> P, GenPolynomial<C> A);


    /**
     * Is in Normalform.
     * @param Pp polynomial list.
     * @return true if each A in Pp is in normalform with respect to Pp\{A}.
     */
    public boolean isNormalform(List<GenPolynomial<C>> Pp);


    /**
     * Normalform.
     * @param A polynomial.
     * @param P polynomial list.
     * @return nf(A) with respect to P.
     */
    public GenPolynomial<C> normalform(List<GenPolynomial<C>> P, GenPolynomial<C> A);


    /**
     * Normalform Set.
     * @param Ap polynomial list.
     * @param Pp polynomial list.
     * @return list of nf(a) with respect to Pp for all a in Ap.
     */
    public List<GenPolynomial<C>> normalform(List<GenPolynomial<C>> Pp, List<GenPolynomial<C>> Ap);


    /**
     * Normalform with recording.
     * @param row recording matrix, is modified.
     * @param Pp a polynomial list for reduction.
     * @param Ap a polynomial.
     * @return nf(Pp,Ap), the normal form of Ap wrt. Pp.
     */
    public GenPolynomial<C> normalform(List<GenPolynomial<C>> row, List<GenPolynomial<C>> Pp,
                    GenPolynomial<C> Ap);


    /**
     * Irreducible set.
     * @param Pp polynomial list.
     * @return a list P of polynomials which are in normalform wrt. P and with
     *         ideal(Pp) = ideal(P).
     */
    public List<GenPolynomial<C>> irreducibleSet(List<GenPolynomial<C>> Pp);


    /**
     * Is reduction of normal form.
     * @param row recording matrix, is modified.
     * @param Pp a polynomial list for reduction.
     * @param Ap a polynomial.
     * @param Np nf(Pp,Ap), a normal form of Ap wrt. Pp.
     * @return true, if Np + sum( row[i]*Pp[i] ) == Ap, else false.
     */

    public boolean isReductionNF(List<GenPolynomial<C>> row, List<GenPolynomial<C>> Pp, GenPolynomial<C> Ap,
                    GenPolynomial<C> Np);

}
