/*
 * Redberry: symbolic tensor computations.
 *
 * Copyright (c) 2010-2015:
 *   Stanislav Poslavsky   
 *   Bolotin Dmitriy       
 *
 * This file is part of Redberry.
 *
 * Redberry is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Redberry 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 Redberry. If not, see .
 */
package cc.redberry.core.transformations.fractions;

import cc.redberry.core.number.Complex;
import cc.redberry.core.number.NumberUtils;
import cc.redberry.core.tensor.*;
import cc.redberry.core.utils.Indicator;
import cc.redberry.core.utils.TensorUtils;

import java.util.ArrayList;
import java.util.List;

/**
 * Gives the numerator and denominator of expression.
 *
 * @author Dmitry Bolotin
 * @author Stanislav Poslavsky
 */
public final class NumeratorDenominator {
    public final Tensor numerator, denominator;

    private NumeratorDenominator(Tensor numerator, Tensor denominator) {
        this.numerator = numerator;
        this.denominator = denominator;
    }

    public Tensor getNumerator() {
        return numerator;
    }

    public Tensor getDenominator() {
        return denominator;
    }

    public static NumeratorDenominator getNumeratorAndDenominator(Tensor tensor) {
        return getNumeratorAndDenominator(tensor, defaultDenominatorIndicator);
    }

    public static NumeratorDenominator getNumeratorAndDenominator(Tensor tensor, Indicator denominatorIndicator) {
        if (denominatorIndicator.is(tensor))
            return new NumeratorDenominator(Complex.ONE, Tensors.reciprocal(tensor));

        if (tensor instanceof Power && tensor.get(1) instanceof Sum) {
            List powers = expandPower(tensor);
            TensorBuilder denominator = new ProductBuilder(),
                    numerator = new ProductBuilder();
            for (Tensor power : powers)
                if (denominatorIndicator.is(power))
                    denominator.put(Tensors.reciprocal(power));
                else
                    numerator.put(power);
            return new NumeratorDenominator(numerator.build(), denominator.build());
        }

        if (!(tensor instanceof Product))
            return new NumeratorDenominator(tensor, Complex.ONE);

        ProductBuilder denominators = new ProductBuilder();
        Tensor temp = tensor;
        Tensor t;
        Tensor exponent;
        for (int i = tensor.size() - 1; i >= 0; --i) {
            t = tensor.get(i);
            if (denominatorIndicator.is(t)) {
                exponent = Tensors.negate(t.get(1));
                denominators.put(Tensors.pow(t.get(0), exponent));
                if (temp instanceof Product)
                    temp = ((Product) temp).remove(i);
                else
                    temp = Complex.ONE;
            }
        }
        return new NumeratorDenominator(temp, denominators.build());
    }

    private static List expandPower(Tensor power) {
        List powers = new ArrayList<>(power.get(1).size());
        for (Tensor exponent : power.get(1))
            powers.add(Tensors.pow(power.get(0), exponent));
        return powers;
    }

    public static Indicator defaultDenominatorIndicator = new Indicator() {
        @Override
        public boolean is(Tensor tensor) {
            if (tensor instanceof Power) {
                Tensor exponent = tensor.get(1);
                if (exponent instanceof Complex)
                    return NumberUtils.isRealNegative((Complex) exponent);
                if (exponent instanceof Product)
                    return ((Product) exponent).getFactor().isMinusOne();
            }
            return false;
        }
    };

    public static Indicator integerDenominatorIndicator = new Indicator() {
        @Override
        public boolean is(Tensor tensor) {
            return TensorUtils.isNegativeIntegerPower(tensor);
        }
    };
}