/*
 * $Id$
 */

package edu.jas.gbufd;


import org.apache.log4j.Logger;

import edu.jas.arith.BigInteger;
import edu.jas.arith.BigRational;
import edu.jas.arith.ModInteger;
import edu.jas.arith.ModIntegerRing;
import edu.jas.arith.ModLong;
import edu.jas.arith.ModLongRing;
import edu.jas.arith.Product;
import edu.jas.arith.ProductRing;
import edu.jas.gb.DGroebnerBaseSeq;
import edu.jas.gb.EGroebnerBaseSeq;
import edu.jas.gb.GBProxy;
import edu.jas.gb.GroebnerBaseAbstract;
import edu.jas.gb.GroebnerBaseParallel;
import edu.jas.gb.GroebnerBaseSeq;
import edu.jas.gb.OrderedPairlist;
import edu.jas.gb.PairList;
import edu.jas.gb.ReductionSeq;
import edu.jas.kern.ComputerThreads;
import edu.jas.poly.GenPolynomial;
import edu.jas.poly.GenPolynomialRing;
import edu.jas.structure.GcdRingElem;
import edu.jas.structure.RingElem;
import edu.jas.structure.RingFactory;
import edu.jas.ufd.Quotient;
import edu.jas.ufd.QuotientRing;


/**
 * Groebner bases algorithms factory. Select appropriate Groebner bases engine
 * based on the coefficient types.
 * @author Heinz Kredel
 * @usage To create objects that implement the GroebnerBase
 *        interface use the GBFactory. It will select an
 *        appropriate implementation based on the types of polynomial
 *        coefficients C. The method to obtain an implementation is
 *        getImplementation(). getImplementation()
 *        returns an object of a class which implements the
 *        GroebnerBase interface, more precisely an object of
 *        abstract class GroebnerBaseAbstract.
 * 
 *        
 * 
 * GroebnerBase<CT> engine;
 * engine = GBFactory.<CT> getImplementation(cofac);
 * c = engine.GB(A);
 * 
 * 
 *        For example, if the coefficient type is BigInteger, the usage looks
 *        like
 * 
 *        
 * 
 * BigInteger cofac = new BigInteger();
 * GroebnerBase<BigInteger> engine;
 * engine = GBFactory.getImplementation(cofac);
 * c = engine.GB(A);
 * 
 * 
 * @see edu.jas.gb.GroebnerBase
 * @see edu.jas.application.GBAlgorithmBuilder
 */

public class GBFactory {


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


    /**
     * Algorithm indicators: igb = integerGB, egb = e-GB, dgb = d-GB, qgb =
     * fraction coefficients GB, ffgb = fraction free GB.
     */
    public static enum Algo {
        igb, egb, dgb, qgb, ffgb
    };


    /**
     * Protected factory constructor.
     */
    protected GBFactory() {
    }


    /**
     * Determine suitable implementation of GB algorithms, no factory case.
     * @return GB algorithm implementation for field coefficients.
     */
    public static > GroebnerBaseAbstract getImplementation() {
        logger.warn("no coefficent factory given, assuming field coeffcients");
        GroebnerBaseAbstract bba = new GroebnerBaseSeq();
        return bba;
    }


    /**
     * Determine suitable implementation of GB algorithms, case ModLong.
     * @param fac ModLongRing.
     * @return GB algorithm implementation.
     */
    public static GroebnerBaseAbstract getImplementation(ModLongRing fac) {
        return getImplementation(fac, new OrderedPairlist());
    }


    /**
     * Determine suitable implementation of GB algorithms, case ModLong.
     * @param fac ModLongRing.
     * @param pl pair selection strategy
     * @return GB algorithm implementation.
     */
    public static GroebnerBaseAbstract getImplementation(ModLongRing fac, PairList pl) {
        GroebnerBaseAbstract bba;
        if (fac.isField()) {
            bba = new GroebnerBaseSeq(pl);
        } else {
            bba = new GroebnerBasePseudoSeq(fac, pl);
        }
        return bba;
    }


    /**
     * Determine suitable implementation of GB algorithms, case ModInteger.
     * @param fac ModIntegerRing.
     * @return GB algorithm implementation.
     */
    public static GroebnerBaseAbstract getImplementation(ModIntegerRing fac) {
        return getImplementation(fac, new OrderedPairlist());
    }


    /**
     * Determine suitable implementation of GB algorithms, case ModInteger.
     * @param fac ModIntegerRing.
     * @param pl pair selection strategy
     * @return GB algorithm implementation.
     */
    public static GroebnerBaseAbstract getImplementation(ModIntegerRing fac,
                    PairList pl) {
        GroebnerBaseAbstract bba;
        if (fac.isField()) {
            bba = new GroebnerBaseSeq(pl);
        } else {
            bba = new GroebnerBasePseudoSeq(fac, pl);
        }
        return bba;
    }


    /**
     * Determine suitable implementation of GB algorithms, case BigInteger.
     * @param fac BigInteger.
     * @return GB algorithm implementation.
     */
    public static GroebnerBaseAbstract getImplementation(BigInteger fac) {
        return getImplementation(fac, Algo.igb);
    }


    /**
     * Determine suitable implementation of GB algorithms, case BigInteger.
     * @param fac BigInteger.
     * @param a algorithm, a = igb, egb, dgb.
     * @return GB algorithm implementation.
     */
    public static GroebnerBaseAbstract getImplementation(BigInteger fac, Algo a) {
        return getImplementation(fac, a, new OrderedPairlist());
    }


    /**
     * Determine suitable implementation of GB algorithms, case BigInteger.
     * @param fac BigInteger.
     * @param pl pair selection strategy
     * @return GB algorithm implementation.
     */
    public static GroebnerBaseAbstract getImplementation(BigInteger fac, PairList pl) {
        return getImplementation(fac, Algo.igb, pl);
    }


    /**
     * Determine suitable implementation of GB algorithms, case BigInteger.
     * @param fac BigInteger.
     * @param a algorithm, a = igb, egb, dgb.
     * @param pl pair selection strategy
     * @return GB algorithm implementation.
     */
    public static GroebnerBaseAbstract getImplementation(BigInteger fac, Algo a,
                    PairList pl) {
        GroebnerBaseAbstract bba;
        switch (a) {
        case igb:
            bba = new GroebnerBasePseudoSeq(fac, pl);
            break;
        case egb:
            bba = new EGroebnerBaseSeq(); // pl not suitable
            break;
        case dgb:
            bba = new DGroebnerBaseSeq(); // pl not suitable
            break;
        default:
            throw new IllegalArgumentException("algorithm not available for BigInteger " + a);
        }
        return bba;
    }


    /**
     * Determine suitable implementation of GB algorithms, case BigRational.
     * @param fac BigRational.
     * @return GB algorithm implementation.
     */
    public static GroebnerBaseAbstract getImplementation(BigRational fac) {
        return getImplementation(fac, Algo.qgb);
    }


    /**
     * Determine suitable implementation of GB algorithms, case BigRational.
     * @param fac BigRational.
     * @param a algorithm, a = qgb, ffgb.
     * @return GB algorithm implementation.
     */
    public static GroebnerBaseAbstract getImplementation(BigRational fac, Algo a) {
        return getImplementation(fac, a, new OrderedPairlist());
    }


    /**
     * Determine suitable implementation of GB algorithms, case BigRational.
     * @param fac BigRational.
     * @param pl pair selection strategy
     * @return GB algorithm implementation.
     */
    public static GroebnerBaseAbstract getImplementation(BigRational fac,
                    PairList pl) {
        return getImplementation(fac, Algo.qgb, pl);
    }


    /**
     * Determine suitable implementation of GB algorithms, case BigRational.
     * @param fac BigRational.
     * @param a algorithm, a = qgb, ffgb.
     * @param pl pair selection strategy
     * @return GB algorithm implementation.
     */
    public static GroebnerBaseAbstract getImplementation(BigRational fac, Algo a,
                    PairList pl) {
        GroebnerBaseAbstract bba;
        switch (a) {
        case qgb:
            bba = new GroebnerBaseSeq(pl);
            break;
        case ffgb:
            bba = new GroebnerBaseRational(); // pl not possible
            break;
        default:
            throw new IllegalArgumentException("algorithm not available for BigRational " + a);
        }
        return bba;
    }


    /**
     * Determine suitable implementation of GB algorithms, case Quotient
     * coefficients.
     * @param fac QuotientRing.
     * @return GB algorithm implementation.
     */
    public static > GroebnerBaseAbstract> getImplementation(
                    QuotientRing fac) {
        return getImplementation(fac, Algo.qgb);
    }


    /**
     * Determine suitable implementation of GB algorithms, case Quotient
     * coefficients.
     * @param fac QuotientRing.
     * @param a algorithm, a = qgb, ffgb.
     * @return GB algorithm implementation.
     */
    public static > GroebnerBaseAbstract> getImplementation(
                    QuotientRing fac, Algo a) {
        return getImplementation(fac, a, new OrderedPairlist>());
    }


    /**
     * Determine suitable implementation of GB algorithms, case Quotient
     * coefficients.
     * @param fac QuotientRing.
     * @param pl pair selection strategy
     * @return GB algorithm implementation.
     */
    public static > GroebnerBaseAbstract> getImplementation(
                    QuotientRing fac, PairList> pl) {
        return getImplementation(fac, Algo.qgb, pl);
    }


    /**
     * Determine suitable implementation of GB algorithms, case Quotient
     * coefficients.
     * @param fac QuotientRing.
     * @param a algorithm, a = qgb, ffgb.
     * @param pl pair selection strategy
     * @return GB algorithm implementation.
     */
    public static > GroebnerBaseAbstract> getImplementation(
                    QuotientRing fac, Algo a, PairList> pl) {
        GroebnerBaseAbstract> bba;
        switch (a) {
        case qgb:
            bba = new GroebnerBaseSeq>(new ReductionSeq>(), pl);
            break;
        case ffgb:
            bba = new GroebnerBaseSeqQuotient(fac); // pl not possible
            break;
        default:
            throw new IllegalArgumentException("algorithm not available for Quotient " + a);
        }
        return bba;
    }


    /**
     * Determine suitable implementation of GB algorithms, case (recursive)
     * polynomial.
     * @param fac GenPolynomialRing<C>.
     * @return GB algorithm implementation.
     */
    public static > GroebnerBaseAbstract> getImplementation(
                    GenPolynomialRing fac) {
        GroebnerBaseAbstract> bba;
        bba = new GroebnerBasePseudoRecSeq(fac);
        return bba;
    }


    /**
     * Determine suitable implementation of GB algorithms, case regular rings.
     * @param fac RegularRing.
     * @return GB algorithm implementation.
     */
    public static > GroebnerBaseAbstract> getImplementation(
                    ProductRing fac) {
        GroebnerBaseAbstract> bba;
        if (fac.onlyFields()) {
            bba = new RGroebnerBaseSeq>();
        } else {
            bba = new RGroebnerBasePseudoSeq>(fac);
        }
        return bba;
    }


    /**
     * Determine suitable implementation of GB algorithms, other cases.
     * @param fac RingFactory<C>.
     * @return GB algorithm implementation.
     */
    public static > // interface RingElem not sufficient 
    GroebnerBaseAbstract getImplementation(RingFactory fac) {
        return getImplementation(fac, new OrderedPairlist());
    }


    /**
     * Determine suitable implementation of GB algorithms, other cases.
     * @param fac RingFactory<C>.
     * @param pl pair selection strategy
     * @return GB algorithm implementation.
     */
    @SuppressWarnings("unchecked")
    public static > // interface RingElem not sufficient 
    GroebnerBaseAbstract getImplementation(RingFactory fac, PairList pl) {
        logger.debug("fac = " + fac.getClass().getName());
        if (fac.isField()) {
            return new GroebnerBaseSeq(pl);
        }
        GroebnerBaseAbstract bba = null;
        Object ofac = fac;
        if (ofac instanceof GenPolynomialRing) {
            GenPolynomialRing rofac = (GenPolynomialRing) ofac;
            GroebnerBaseAbstract> bbr = new GroebnerBasePseudoRecSeq(rofac); // no pl
            bba = (GroebnerBaseAbstract) bbr;
        } else if (ofac instanceof ProductRing) {
            ProductRing pfac = (ProductRing) ofac;
            if (pfac.onlyFields()) {
                bba = new RGroebnerBaseSeq>();
            } else {
                bba = new RGroebnerBasePseudoSeq>(pfac);
            }
        } else {
            bba = new GroebnerBasePseudoSeq(fac, pl);
        }
        logger.debug("bba = " + bba.getClass().getName());
        return bba;
    }


    /**
     * Determine suitable concurrent implementation of GB algorithms if
     * possible.
     * @param fac RingFactory<C>.
     * @return GB proxy algorithm implementation.
     */
    public static > // interface RingElem not sufficient 
    GroebnerBaseAbstract getProxy(RingFactory fac) {
        return getProxy(fac, new OrderedPairlist());
    }


    /**
     * Determine suitable concurrent implementation of GB algorithms if
     * possible.
     * @param fac RingFactory<C>.
     * @param pl pair selection strategy
     * @return GB proxy algorithm implementation.
     */
    public static > // interface RingElem not sufficient 
    GroebnerBaseAbstract getProxy(RingFactory fac, PairList pl) {
        if (ComputerThreads.NO_THREADS) {
            return GBFactory. getImplementation(fac, pl);
        }
        logger.debug("fac = " + fac.getClass().getName());
        int th = (ComputerThreads.N_CPUS > 2 ? ComputerThreads.N_CPUS - 1 : 2);
        if (fac.isField()) {
            GroebnerBaseAbstract e1 = new GroebnerBaseSeq(pl);
            GroebnerBaseAbstract e2 = new GroebnerBaseParallel(th, pl);
            return new GBProxy(e1, e2);
        } else if (fac.characteristic().signum() == 0) {
            GroebnerBaseAbstract e1 = new GroebnerBasePseudoSeq(fac, pl);
            GroebnerBaseAbstract e2 = new GroebnerBasePseudoParallel(th, fac, pl);
            return new GBProxy(e1, e2);
        }
        return getImplementation(fac);
    }

}