/*
 * $Id$
 */

package edu.jas.ufd;


import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;

import edu.jas.poly.AlgebraicNumber;
import edu.jas.poly.AlgebraicNumberRing;
import edu.jas.poly.GenPolynomial;
import edu.jas.poly.GenPolynomialRing;
import edu.jas.poly.PolyUtil;
import edu.jas.structure.GcdRingElem;
import edu.jas.structure.RingFactory;


/**
 * Absolute factorization algorithms class. This class contains implementations
 * of methods for factorization over algebraically closed fields. The required
 * field extension is computed along with the factors. The methods have been
 * tested for prime fields of characteristic zero, that is for
 * <code>BigRational</code>. It might eventually also be used for prime fields
 * of non-zero characteristic, that is with <code>ModInteger</code>. The field
 * extension may yet not be minimal.
 * @author Heinz Kredel
 * @param <C> coefficient type
 */

public abstract class FactorAbsolute<C extends GcdRingElem<C>> extends FactorAbstract<C> {


    private static final Logger logger = LogManager.getLogger(FactorAbsolute.class);


    private static final boolean debug = logger.isDebugEnabled();


    /*     
     * Factorization engine for algebraic number coefficients.
     */
    //not possible here because of recursion AN -> Int|Mod -> AN -> ...
    //public final FactorAbstract<AlgebraicNumber<C>> aengine;

    /**
     * No argument constructor. <b>Note:</b> can't use this constructor.
     */
    protected FactorAbsolute() {
        throw new IllegalArgumentException("don't use this constructor");
    }


    /**
     * Constructor.
     * @param cfac coefficient ring factory.
     */
    public FactorAbsolute(RingFactory<C> cfac) {
        super(cfac);
        //GenPolynomialRing<C> fac = new GenPolynomialRing<C>(cfac,1);
        //GenPolynomial<C> p = fac.univariate(0);
        //AlgebraicNumberRing<C> afac = new AlgebraicNumberRing<C>(p);
        //aengine = null; //FactorFactory.<C>getImplementation(afac); // hack
    }


    /**
     * Get the String representation.
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        return getClass().getName();
    }


    /**
     * GenPolynomial test if is absolute irreducible.
     * @param P GenPolynomial.
     * @return true if P is absolute irreducible, else false.
     */
    public boolean isAbsoluteIrreducible(GenPolynomial<C> P) {
        if (!isIrreducible(P)) {
            return false;
        }
        Factors<C> F = factorsAbsoluteIrreducible(P);
        if (F.afac == null) {
            return true;
        } else if (F.afactors.size() > 2) {
            return false;
        } else { //F.size() == 2
            boolean cnst = false;
            for (GenPolynomial<AlgebraicNumber<C>> p : F.afactors) {
                if (p.isConstant()) {
                    cnst = true;
                }
            }
            return cnst;
        }
    }


    /**
     * GenPolynomial absolute base factorization of a polynomial.
     * @param P univariate GenPolynomial.
     * @return factors map container: [p_1 -&gt; e_1, ..., p_k -&gt; e_k] with P
     *         = prod_{i=1,...,k} p_i**e_i. <b>Note:</b> K(alpha) not yet
     *         minimal.
     */
    // @Override
    public FactorsMap<C> baseFactorsAbsolute(GenPolynomial<C> P) {
        if (P == null) {
            throw new IllegalArgumentException(this.getClass().getName() + " P == null");
        }
        SortedMap<GenPolynomial<C>, Long> factors = new TreeMap<GenPolynomial<C>, Long>();
        if (P.isZERO()) {
            return new FactorsMap<C>(P, factors);
        }
        //System.out.println("\nP_base = " + P);
        GenPolynomialRing<C> pfac = P.ring; // K[x]
        if (pfac.nvar > 1) {
            //System.out.println("\nfacs_base: univ");
            throw new IllegalArgumentException("only for univariate polynomials");
        }
        if (!pfac.coFac.isField()) {
            //System.out.println("\nfacs_base: field");
            throw new IllegalArgumentException("only for field coefficients");
        }
        if (P.degree(0) <= 1) {
            factors.put(P, 1L);
            return new FactorsMap<C>(P, factors);
        }
        // factor over K (=C)
        SortedMap<GenPolynomial<C>, Long> facs = baseFactors(P);
        if (debug && !isFactorization(P, facs)) {
            System.out.println("facs   = " + facs);
            throw new ArithmeticException("isFactorization = false");
        }
        logger.info("all K factors = {}", facs); // Q[X]
        // factor over some K(alpha)
        SortedMap<Factors<C>, Long> afactors = new TreeMap<Factors<C>, Long>();
        for (Map.Entry<GenPolynomial<C>, Long> me : facs.entrySet()) {
            GenPolynomial<C> p = me.getKey();
            Long e = me.getValue(); //facs.get(p);
            if (p.degree(0) <= 1) {
                factors.put(p, e);
            } else {
                Factors<C> afacs = baseFactorsAbsoluteIrreducible(p);
                //System.out.println("afacs   = " + afacs);
                afactors.put(afacs, e);
            }
        }
        //System.out.println("K(alpha) factors = " + factors);
        return new FactorsMap<C>(P, factors, afactors);
    }


    /**
     * GenPolynomial absolute base factorization of a squarefree polynomial.
     * @param P squarefree and primitive univariate GenPolynomial.
     * @return factors list container: [p_1,...,p_k] with P = prod_{i=1, ..., k}
     *         p_i. <b>Note:</b> K(alpha) not yet minimal.
     */
    // @Override
    public FactorsList<C> baseFactorsAbsoluteSquarefree(GenPolynomial<C> P) {
        if (P == null) {
            throw new IllegalArgumentException(this.getClass().getName() + " P == null");
        }
        List<GenPolynomial<C>> factors = new ArrayList<GenPolynomial<C>>();
        if (P.isZERO()) {
            return new FactorsList<C>(P, factors);
        }
        //System.out.println("\nP_base_sqf = " + P);
        GenPolynomialRing<C> pfac = P.ring; // K[x]
        if (pfac.nvar > 1) {
            //System.out.println("facs_base_sqf: univ");
            throw new IllegalArgumentException("only for univariate polynomials");
        }
        if (!pfac.coFac.isField()) {
            //System.out.println("facs_base_sqf: field");
            throw new IllegalArgumentException("only for field coefficients");
        }
        if (P.degree(0) <= 1) {
            factors.add(P);
            return new FactorsList<C>(P, factors);
        }
        // factor over K (=C)
        List<GenPolynomial<C>> facs = baseFactorsSquarefree(P);
        //System.out.println("facs_base_irred = " + facs);
        if (debug && !isFactorization(P, facs)) {
            throw new ArithmeticException("isFactorization = false");
        }
        logger.info("all K factors = {}", facs); // Q[X]
        // factor over K(alpha)
        List<Factors<C>> afactors = new ArrayList<Factors<C>>();
        for (GenPolynomial<C> p : facs) {
            //System.out.println("facs_base_sqf_p = " + p);
            if (p.degree(0) <= 1) {
                factors.add(p);
            } else {
                Factors<C> afacs = baseFactorsAbsoluteIrreducible(p);
                //System.out.println("afacs_base_sqf = " + afacs);
                logger.info("K(alpha) factors = {}", afacs); // K(alpha)[X]
                afactors.add(afacs);
            }
        }
        //System.out.println("K(alpha) factors = " + factors);
        return new FactorsList<C>(P, factors, afactors);
    }


    /**
     * GenPolynomial base absolute factorization of a irreducible polynomial.
     * @param P irreducible! univariate GenPolynomial.
     * @return factors container: [p_1,...,p_k] with P = prod_{i=1, ..., k} p_i
     *         in K(alpha)[x] for suitable alpha and p_i irreducible over L[x],
     *         where K \subset K(alpha) \subset L is an algebraically closed
     *         field over K. <b>Note:</b> K(alpha) not yet minimal.
     */
    public Factors<C> baseFactorsAbsoluteIrreducible(GenPolynomial<C> P) {
        if (P == null) {
            throw new IllegalArgumentException(this.getClass().getName() + " P == null");
        }
        if (P.isZERO()) {
            return new Factors<C>(P);
        }
        //System.out.println("\nP_base_irred = " + P);
        GenPolynomialRing<C> pfac = P.ring; // K[x]
        if (pfac.nvar > 1) {
            //System.out.println("facs_base_irred: univ");
            throw new IllegalArgumentException("only for univariate polynomials");
        }
        if (!pfac.coFac.isField()) {
            //System.out.println("facs_base_irred: field");
            throw new IllegalArgumentException("only for field coefficients");
        }
        if (P.degree(0) <= 1) {
            return new Factors<C>(P);
        }
        // setup field extension K(alpha) where alpha = z_xx
        //String[] vars = new String[] { "z_" + Math.abs(P.hashCode() % 1000) };
        String[] vars = pfac.newVars("z_");
        pfac = pfac.copy();
        vars = pfac.setVars(vars);
        GenPolynomial<C> aP = pfac.copy(P); // hack to exchange the variables
        AlgebraicNumberRing<C> afac = new AlgebraicNumberRing<C>(aP, true); // since irreducible
        if (logger.isInfoEnabled()) {
            logger.info("K(alpha) = {}", afac);
            logger.info("K(alpha) = {}", afac.toScript());
        }
        GenPolynomialRing<AlgebraicNumber<C>> pafac = new GenPolynomialRing<AlgebraicNumber<C>>(afac,
                        aP.ring.nvar, aP.ring.tord, /*old*/vars);
        // convert to K(alpha)
        GenPolynomial<AlgebraicNumber<C>> Pa = PolyUtil.<C> convertToAlgebraicCoefficients(pafac, P);
        logger.info("P over K(alpha) = {}", Pa);
        // factor over K(alpha)
        FactorAbstract<AlgebraicNumber<C>> engine = FactorFactory.<C> getImplementation(afac);
        //System.out.println("K(alpha) engine = " + engine);
        List<GenPolynomial<AlgebraicNumber<C>>> factors = engine.baseFactorsSquarefree(Pa);
        //System.out.println("factors = " + factors);
        logger.info("factors over K(alpha) = {}", factors);
        List<GenPolynomial<AlgebraicNumber<C>>> faca = new ArrayList<GenPolynomial<AlgebraicNumber<C>>>(
                        factors.size());
        List<Factors<AlgebraicNumber<C>>> facar = new ArrayList<Factors<AlgebraicNumber<C>>>();
        for (GenPolynomial<AlgebraicNumber<C>> fi : factors) {
            if (fi.degree(0) <= 1) {
                faca.add(fi);
            } else {
                //System.out.println("fi.deg > 1 = " + fi);
                FactorAbsolute<AlgebraicNumber<C>> aengine = (FactorAbsolute<AlgebraicNumber<C>>) FactorFactory
                                .<C> getImplementation(afac);
                Factors<AlgebraicNumber<C>> fif = aengine.baseFactorsAbsoluteIrreducible(fi);
                //System.out.println("fif = " + fif);
                facar.add(fif);
            }
        }
        if (facar.size() == 0) {
            facar = null;
        }
        // find minimal field extension K(beta) \subset K(alpha)
        return new Factors<C>(P, afac, Pa, faca, facar);
    }


    /**
     * Univariate GenPolynomial algebraic partial fraction decomposition,
     * Absolute factorization for elementary integration algorithm to linear
     * factors.
     * @param A univariate GenPolynomial, deg(A) &le; deg(P).
     * @param P univariate squarefree GenPolynomial, gcd(A,P) == 1.
     * @return partial fraction container.
     */
    public PartialFraction<C> baseAlgebraicPartialFraction(GenPolynomial<C> A, GenPolynomial<C> P) {
        if (P == null || P.isZERO()) {
            throw new IllegalArgumentException(" P == null or P == 0");
        }
        if (A == null || A.isZERO()) {
            throw new IllegalArgumentException(" A == null or A == 0");
            // PartialFraction(A,P,al,pl,empty,empty)
        }
        //System.out.println("\nP_base_algeb_part = " + P);
        GenPolynomialRing<C> pfac = P.ring; // K[x]
        if (pfac.nvar > 1) {
            //System.out.println("facs_base_irred: univ");
            throw new IllegalArgumentException("only for univariate polynomials");
        }
        if (!pfac.coFac.isField()) {
            //System.out.println("facs_base_irred: field");
            throw new IllegalArgumentException("only for field coefficients");
        }
        List<C> cfactors = new ArrayList<C>();
        List<GenPolynomial<C>> cdenom = new ArrayList<GenPolynomial<C>>();
        List<AlgebraicNumber<C>> afactors = new ArrayList<AlgebraicNumber<C>>();
        List<GenPolynomial<AlgebraicNumber<C>>> adenom = new ArrayList<GenPolynomial<AlgebraicNumber<C>>>();

        // P linear
        if (P.degree(0) <= 1) {
            cfactors.add(A.leadingBaseCoefficient());
            cdenom.add(P);
            return new PartialFraction<C>(A, P, cfactors, cdenom, afactors, adenom);
        }
        List<GenPolynomial<C>> Pfac = baseFactorsSquarefree(P);
        //System.out.println("\nPfac = " + Pfac);

        List<GenPolynomial<C>> Afac = engine.basePartialFraction(A, Pfac);

        GenPolynomial<C> A0 = Afac.remove(0);
        if (!A0.isZERO()) {
            throw new ArithmeticException(" A0 != 0: deg(A)>= deg(P)");
        }

        // algebraic and linear factors
        int i = 0;
        for (GenPolynomial<C> pi : Pfac) {
            GenPolynomial<C> ai = Afac.get(i++);
            if (pi.degree(0) <= 1) {
                cfactors.add(ai.leadingBaseCoefficient());
                cdenom.add(pi);
                continue;
            }
            PartialFraction<C> pf = baseAlgebraicPartialFractionIrreducibleAbsolute(ai, pi);
            //PartialFraction<C> pf = baseAlgebraicPartialFractionIrreducible(ai,pi);
            cfactors.addAll(pf.cfactors);
            cdenom.addAll(pf.cdenom);
            afactors.addAll(pf.afactors);
            adenom.addAll(pf.adenom);
        }
        return new PartialFraction<C>(A, P, cfactors, cdenom, afactors, adenom);
    }


    /**
     * Univariate GenPolynomial algebraic partial fraction decomposition, via
     * absolute factorization to linear factors.
     * @param A univariate GenPolynomial, deg(A) &lt; deg(P).
     * @param P univariate irreducible GenPolynomial, gcd(A,P) == 1.
     * @return partial fraction container.
     */
    @SuppressWarnings("unchecked")
    public PartialFraction<C> baseAlgebraicPartialFractionIrreducibleAbsolute(GenPolynomial<C> A,
                    GenPolynomial<C> P) {
        if (P == null || P.isZERO()) {
            throw new IllegalArgumentException(" P == null or P == 0");
        }
        //System.out.println("\nP_base_algeb_part = " + P);
        GenPolynomialRing<C> pfac = P.ring; // K[x]
        if (pfac.nvar > 1) {
            //System.out.println("facs_base_irred: univ");
            throw new IllegalArgumentException("only for univariate polynomials");
        }
        if (!pfac.coFac.isField()) {
            //System.out.println("facs_base_irred: field");
            throw new IllegalArgumentException("only for field coefficients");
        }
        List<C> cfactors = new ArrayList<C>();
        List<GenPolynomial<C>> cdenom = new ArrayList<GenPolynomial<C>>();
        List<AlgebraicNumber<C>> afactors = new ArrayList<AlgebraicNumber<C>>();
        List<GenPolynomial<AlgebraicNumber<C>>> adenom = new ArrayList<GenPolynomial<AlgebraicNumber<C>>>();

        // P linear
        if (P.degree(0) <= 1) {
            cfactors.add(A.leadingBaseCoefficient());
            cdenom.add(P);
            return new PartialFraction<C>(A, P, cfactors, cdenom, afactors, adenom);
        }

        // non linear case
        Factors<C> afacs = factorsAbsoluteIrreducible(P);
        //System.out.println("linear algebraic factors = " + afacs);
        //System.out.println("afactors      = " + afacs.afactors);
        //System.out.println("arfactors     = " + afacs.arfactors);
        //System.out.println("arfactors pol = " + afacs.arfactors.get(0).poly);
        //System.out.println("arfactors2    = " + afacs.arfactors.get(0).afactors);

        List<GenPolynomial<AlgebraicNumber<C>>> fact = afacs.getFactors();
        //System.out.println("factors       = " + fact);
        GenPolynomial<AlgebraicNumber<C>> Pa = afacs.apoly;
        GenPolynomial<AlgebraicNumber<C>> Aa = PolyUtil.<C> convertToRecAlgebraicCoefficients(1, Pa.ring, A);

        GreatestCommonDivisorAbstract<AlgebraicNumber<C>> aengine = GCDFactory.getProxy(afacs.afac);
        //System.out.println("denom         = " + Pa);
        //System.out.println("number         = " + Aa);
        List<GenPolynomial<AlgebraicNumber<C>>> numbers = aengine.basePartialFraction(Aa, fact);
        //System.out.println("part frac     = " + numbers);
        GenPolynomial<AlgebraicNumber<C>> A0 = numbers.remove(0);
        if (!A0.isZERO()) {
            throw new ArithmeticException(" A0 != 0: deg(A)>= deg(P)");
        }
        int i = 0;
        for (GenPolynomial<AlgebraicNumber<C>> fa : fact) {
            GenPolynomial<AlgebraicNumber<C>> an = numbers.get(i++);
            if (fa.degree(0) <= 1) {
                afactors.add(an.leadingBaseCoefficient());
                adenom.add(fa);
                continue;
            }
            System.out.println("fa = " + fa);
            Factors<AlgebraicNumber<C>> faf = afacs.getFactor(fa);
            System.out.println("faf = " + faf);
            List<GenPolynomial<AlgebraicNumber<AlgebraicNumber<C>>>> fafact = faf.getFactors();
            GenPolynomial<AlgebraicNumber<AlgebraicNumber<C>>> Aaa = PolyUtil
                            .<AlgebraicNumber<C>> convertToRecAlgebraicCoefficients(1, faf.apoly.ring, an);

            GreatestCommonDivisorAbstract<AlgebraicNumber<AlgebraicNumber<C>>> aaengine = GCDFactory
                            .getImplementation(faf.afac);

            List<GenPolynomial<AlgebraicNumber<AlgebraicNumber<C>>>> anumers = aaengine
                            .basePartialFraction(Aaa, fafact);
            System.out.println("algeb part frac = " + anumers);
            GenPolynomial<AlgebraicNumber<AlgebraicNumber<C>>> A0a = anumers.remove(0);
            if (!A0a.isZERO()) {
                throw new ArithmeticException(" A0 != 0: deg(A)>= deg(P)");
            }
            int k = 0;
            for (GenPolynomial<AlgebraicNumber<AlgebraicNumber<C>>> faa : fafact) {
                GenPolynomial<AlgebraicNumber<AlgebraicNumber<C>>> ana = anumers.get(k++);
                System.out.println("faa = " + faa);
                System.out.println("ana = " + ana);
                if (faa.degree(0) > 1) {
                    throw new ArithmeticException(" faa not linear");
                }
                GenPolynomial<AlgebraicNumber<C>> ana1 = (GenPolynomial<AlgebraicNumber<C>>) (GenPolynomial) ana;
                GenPolynomial<AlgebraicNumber<C>> faa1 = (GenPolynomial<AlgebraicNumber<C>>) (GenPolynomial) faa;

                afactors.add(ana1.leadingBaseCoefficient());
                adenom.add(faa1);
            }
        }
        return new PartialFraction<C>(A, P, cfactors, cdenom, afactors, adenom);
    }


    /**
     * GenPolynomial absolute factorization of a polynomial.
     * @param P GenPolynomial.
     * @return factors map container: [p_1 -&gt; e_1, ..., p_k -&gt; e_k] with P
     *         = prod_{i=1,...,k} p_i**e_i. <b>Note:</b> K(alpha) not yet
     *         minimal.
     */
    public FactorsMap<C> factorsAbsolute(GenPolynomial<C> P) {
        if (P == null) {
            throw new IllegalArgumentException(this.getClass().getName() + " P == null");
        }
        SortedMap<GenPolynomial<C>, Long> factors = new TreeMap<GenPolynomial<C>, Long>();
        if (P.isZERO()) {
            return new FactorsMap<C>(P, factors);
        }
        //System.out.println("\nP_mult = " + P);
        GenPolynomialRing<C> pfac = P.ring; // K[x]
        if (pfac.nvar <= 1) {
            return baseFactorsAbsolute(P);
        }
        if (!pfac.coFac.isField()) {
            throw new IllegalArgumentException("only for field coefficients");
        }
        if (P.degree() <= 1) {
            factors.put(P, 1L);
            return new FactorsMap<C>(P, factors);
        }
        // factor over K (=C)
        SortedMap<GenPolynomial<C>, Long> facs = factors(P);
        if (debug && !isFactorization(P, facs)) {
            throw new ArithmeticException("isFactorization = false");
        }
        logger.info("all K factors = {}", facs); // Q[X]
        SortedMap<Factors<C>, Long> afactors = new TreeMap<Factors<C>, Long>();
        // factor over K(alpha)
        for (Map.Entry<GenPolynomial<C>, Long> me : facs.entrySet()) {
            GenPolynomial<C> p = me.getKey();
            Long e = me.getValue(); //facs.get(p);
            if (p.degree() <= 1) {
                factors.put(p, e);
            } else {
                Factors<C> afacs = factorsAbsoluteIrreducible(p);
                if (afacs.afac == null) { // absolute irreducible
                    factors.put(p, e);
                } else {
                    afactors.put(afacs, e);
                }
            }
        }
        //System.out.println("K(alpha) factors multi = " + factors);
        return new FactorsMap<C>(P, factors, afactors);
    }


    /**
     * GenPolynomial absolute factorization of a squarefree polynomial.
     * @param P squarefree and primitive GenPolynomial.
     * @return factors list container: [p_1,...,p_k] with P = prod_{i=1, ..., k}
     *         p_i. <b>Note:</b> K(alpha) not yet minimal.
     */
    // @Override
    public FactorsList<C> factorsAbsoluteSquarefree(GenPolynomial<C> P) {
        if (P == null) {
            throw new IllegalArgumentException(this.getClass().getName() + " P == null");
        }
        List<GenPolynomial<C>> factors = new ArrayList<GenPolynomial<C>>();
        if (P.isZERO()) {
            return new FactorsList<C>(P, factors);
        }
        //System.out.println("\nP = " + P);
        GenPolynomialRing<C> pfac = P.ring; // K[x]
        if (pfac.nvar <= 1) {
            return baseFactorsAbsoluteSquarefree(P);
        }
        if (!pfac.coFac.isField()) {
            throw new IllegalArgumentException("only for field coefficients");
        }
        if (P.degree() <= 1) {
            factors.add(P);
            return new FactorsList<C>(P, factors);
        }
        // factor over K (=C)
        List<GenPolynomial<C>> facs = factorsSquarefree(P);
        if (debug && !isFactorization(P, facs)) {
            throw new ArithmeticException("isFactorization = false");
        }
        logger.info("all K factors = {}", facs); // Q[X]
        List<Factors<C>> afactors = new ArrayList<Factors<C>>();
        // factor over K(alpha)
        for (GenPolynomial<C> p : facs) {
            if (p.degree() <= 1) {
                factors.add(p);
            } else {
                Factors<C> afacs = factorsAbsoluteIrreducible(p);
                if (debug) {
                    logger.info("K(alpha) factors = {}", afacs); // K(alpha)[X]
                }
                if (afacs.afac == null) { // absolute irreducible
                    factors.add(p);
                } else {
                    afactors.add(afacs);
                }
            }
        }
        //System.out.println("K(alpha) factors = " + factors);
        return new FactorsList<C>(P, factors, afactors);
    }


    /**
     * GenPolynomial absolute factorization of a irreducible polynomial.
     * @param P irreducible! GenPolynomial.
     * @return factors container: [p_1,...,p_k] with P = prod_{i=1, ..., k} p_i
     *         in K(alpha)[x] for suitable alpha and p_i irreducible over L[x],
     *         where K \subset K(alpha) \subset L is an algebraically closed
     *         field over K. <b>Note:</b> K(alpha) not yet minimal.
     */
    public Factors<C> factorsAbsoluteIrreducible(GenPolynomial<C> P) {
        if (P == null) {
            throw new IllegalArgumentException(this.getClass().getName() + " P == null");
        }
        if (P.isZERO()) {
            return new Factors<C>(P);
        }
        GenPolynomialRing<C> pfac = P.ring; // K[x]
        if (pfac.nvar <= 1) {
            return baseFactorsAbsoluteIrreducible(P);
        }
        if (!pfac.coFac.isField()) {
            throw new IllegalArgumentException("only for field coefficients");
        }
        //List<GenPolynomial<C>> factors = new ArrayList<GenPolynomial<C>>();
        if (P.degree() <= 1) {
            return new Factors<C>(P);
        }
        // find field extension K(alpha)
        GenPolynomial<C> up = P;
        RingFactory<C> cf = pfac.coFac;
        long cr = cf.characteristic().longValueExact(); // char might be larger
        if (cr == 0L) {
            cr = Long.MAX_VALUE;
        }
        long rp = 0L;
        for (int i = 0; i < (pfac.nvar - 1); i++) {
            rp = 0L;
            GenPolynomialRing<C> nfac = pfac.contract(1);
            String[] vn = new String[] { pfac.getVars()[pfac.nvar - 1] };
            GenPolynomialRing<GenPolynomial<C>> rfac = new GenPolynomialRing<GenPolynomial<C>>(nfac, 1,
                            pfac.tord, vn);
            GenPolynomial<GenPolynomial<C>> upr = PolyUtil.<C> recursive(rfac, up);
            //System.out.println("upr = " + upr);
            GenPolynomial<C> ep;
            do {
                if (rp >= cr) {
                    throw new ArithmeticException("elements of prime field exhausted: " + cr);
                }
                C r = cf.fromInteger(rp); //cf.random(rp);
                //System.out.println("r   = " + r);
                ep = PolyUtil.<C> evaluateMainRecursive(nfac, upr, r);
                //System.out.println("ep  = " + ep);
                rp++;
            } while (!isSquarefree(ep) /*todo: || ep.degree() <= 1*/); // max deg
            up = ep;
            pfac = nfac;
        }
        up = up.monic();
        if (debug) {
            logger.info("P({}) = {}", rp, up);
            //System.out.println("up  = " + up);
        }
        if (debug && !isSquarefree(up)) {
            throw new ArithmeticException("not irreducible up = " + up);
        }
        if (up.degree(0) <= 1) {
            return new Factors<C>(P);
        }
        // find irreducible factor of up
        List<GenPolynomial<C>> UF = baseFactorsSquarefree(up);
        //System.out.println("UF  = " + UF);
        FactorsList<C> aUF = baseFactorsAbsoluteSquarefree(up);
        //System.out.println("aUF  = " + aUF);
        AlgebraicNumberRing<C> arfac = aUF.findExtensionField();
        //System.out.println("arfac  = " + arfac);

        long e = up.degree(0);
        // search factor polynomial with smallest degree 
        for (int i = 0; i < UF.size(); i++) {
            GenPolynomial<C> upi = UF.get(i);
            long d = upi.degree(0);
            if (1 <= d && d <= e) {
                up = upi;
                e = up.degree(0);
            }
        }
        if (up.degree(0) <= 1) {
            return new Factors<C>(P);
        }
        if (debug) {
            logger.info("field extension by {}", up);
        }

        List<GenPolynomial<AlgebraicNumber<C>>> afactors = new ArrayList<GenPolynomial<AlgebraicNumber<C>>>();

        // setup field extension K(alpha)
        //String[] vars = new String[] { "z_" + Math.abs(up.hashCode() % 1000) };
        String[] vars = pfac.newVars("z_");
        pfac = pfac.copy();
        //String[] ovars = 
        pfac.setVars(vars); // side effects! 
        //GenPolynomial<C> aup = pfac.copy(up); // hack to exchange the variables
        //AlgebraicNumberRing<C> afac = new AlgebraicNumberRing<C>(aup,true); // since irreducible
        AlgebraicNumberRing<C> afac = arfac;
        int depth = afac.depth();
        //System.out.println("afac = " + afac);
        GenPolynomialRing<AlgebraicNumber<C>> pafac = new GenPolynomialRing<AlgebraicNumber<C>>(afac,
                        P.ring.nvar, P.ring.tord, P.ring.getVars());
        //System.out.println("pafac = " + pafac);
        // convert to K(alpha)
        GenPolynomial<AlgebraicNumber<C>> Pa = PolyUtil.<C> convertToRecAlgebraicCoefficients(depth, pafac,
                        P);
        //System.out.println("Pa = " + Pa);
        // factor over K(alpha)
        FactorAbstract<AlgebraicNumber<C>> engine = FactorFactory.<C> getImplementation(afac);
        afactors = engine.factorsSquarefree(Pa);
        if (debug) {
            logger.info("K(alpha) factors multi = {}", afactors);
        }
        if (afactors.size() <= 1) {
            return new Factors<C>(P);
        }
        // normalize first factor to monic
        GenPolynomial<AlgebraicNumber<C>> p1 = afactors.get(0);
        AlgebraicNumber<C> p1c = p1.leadingBaseCoefficient();
        if (!p1c.isONE()) {
            GenPolynomial<AlgebraicNumber<C>> p2 = afactors.get(1);
            afactors.remove(p1);
            afactors.remove(p2);
            p1 = p1.divide(p1c);
            p2 = p2.multiply(p1c);
            afactors.add(p1);
            afactors.add(p2);
        }
        // recursion for splitting field
        // find minimal field extension K(beta) \subset K(alpha)
        return new Factors<C>(P, afac, Pa, afactors);
    }


    /**
     * GenPolynomial is absolute factorization.
     * @param facs factors container.
     * @return true if P = prod_{i=1,...,r} p_i, else false.
     */
    public boolean isAbsoluteFactorization(Factors<C> facs) {
        if (facs == null) {
            throw new IllegalArgumentException("facs may not be null");
        }
        if (facs.afac == null) {
            return true;
        }
        GenPolynomial<AlgebraicNumber<C>> fa = facs.apoly;
        GenPolynomialRing<AlgebraicNumber<C>> pafac = fa.ring;
        GenPolynomial<AlgebraicNumber<C>> t = pafac.getONE();
        for (GenPolynomial<AlgebraicNumber<C>> f : facs.afactors) {
            t = t.multiply(f);
        }
        //return fa.equals(t) || fa.equals(t.negate());
        boolean b = fa.equals(t) || fa.equals(t.negate());
        if (b) {
            return b;
        }
        if (facs.arfactors == null) {
            return false;
        }
        for (Factors<AlgebraicNumber<C>> arp : facs.arfactors) {
            t = t.multiply(arp.poly);
        }
        b = fa.equals(t) || fa.equals(t.negate());
        if (!b) {
            System.out.println("\nFactors: " + facs);
            System.out.println("fa = " + fa);
            System.out.println("t = " + t);
        }
        return b;
    }


    /**
     * GenPolynomial is absolute factorization.
     * @param facs factors list container.
     * @return true if P = prod_{i=1,...,r} p_i, else false.
     */
    public boolean isAbsoluteFactorization(FactorsList<C> facs) {
        if (facs == null) {
            throw new IllegalArgumentException("facs may not be null");
        }
        GenPolynomial<C> P = facs.poly;
        GenPolynomial<C> t = P.ring.getONE();
        for (GenPolynomial<C> f : facs.factors) {
            t = t.multiply(f);
        }
        if (P.equals(t) || P.equals(t.negate())) {
            return true;
        }
        if (facs.afactors == null) {
            return false;
        }
        for (Factors<C> fs : facs.afactors) {
            if (!isAbsoluteFactorization(fs)) {
                return false;
            }
            t = t.multiply(facs.poly);
        }
        //return P.equals(t) || P.equals(t.negate());
        boolean b = P.equals(t) || P.equals(t.negate());
        if (!b) {
            System.out.println("\nFactorsList: " + facs);
            System.out.println("P = " + P);
            System.out.println("t = " + t);
        }
        return b;
    }


    /**
     * GenPolynomial is absolute factorization.
     * @param facs factors map container.
     * @return true if P = prod_{i=1,...,k} p_i**e_i , else false.
     */
    public boolean isAbsoluteFactorization(FactorsMap<C> facs) {
        if (facs == null) {
            throw new IllegalArgumentException("facs may not be null");
        }
        GenPolynomial<C> P = facs.poly;
        GenPolynomial<C> t = P.ring.getONE();
        for (Map.Entry<GenPolynomial<C>, Long> me : facs.factors.entrySet()) {
            GenPolynomial<C> f = me.getKey();
            long e = me.getValue();
            GenPolynomial<C> g = f.power(e);
            t = t.multiply(g);
        }
        if (P.equals(t) || P.equals(t.negate())) {
            return true;
        }
        if (facs.afactors == null) {
            return false;
        }
        for (Map.Entry<Factors<C>, Long> me : facs.afactors.entrySet()) {
            Factors<C> fs = me.getKey();
            if (!isAbsoluteFactorization(fs)) {
                return false;
            }
            long e = me.getValue();
            GenPolynomial<C> g = fs.poly.power(e);
            t = t.multiply(g);
        }
        boolean b = P.equals(t) || P.equals(t.negate());
        if (!b) {
            System.out.println("\nFactorsMap: " + facs);
            System.out.println("P = " + P);
            System.out.println("t = " + t);
        }
        return b;
    }

}
