/*
 * Units of Measurement Reference Implementation
 * Copyright (c) 2005-2021, Jean-Marie Dautelle, Werner Keil, Otavio Santana.
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions
 *    and the following disclaimer in the documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of JSR-385, Indriya nor the names of their contributors may be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package tech.units.indriya.function;

import java.math.BigInteger;
import java.util.Objects;

import javax.measure.Prefix;
import javax.measure.UnitConverter;

import tech.units.indriya.internal.function.Calculator;
import tech.uom.lib.common.function.IntBaseSupplier;
import tech.uom.lib.common.function.IntExponentSupplier;

/**
 * UnitConverter for numbers in base^exponent representation.
 * @author Andi Huber
 * @author Werner Keil
 * @version 2.0, Oct 8, 2020
 * @since 2.0
 */
// As it's used in the "format" package, we may not be able to make it package-private here
public final class PowerOfIntConverter extends AbstractConverter 
 implements MultiplyConverter, IntBaseSupplier, IntExponentSupplier {
        private static final long serialVersionUID = 3546932001671571300L;

        private final int base;
        private final int exponent;
        private final int hashCode;
        private final RationalNumber rationalFactor;

        /**
         * Creates a converter with the specified Prefix.
         * 
         * @param prefix
         *            the prefix for the factor.
         */
        static PowerOfIntConverter of(Prefix prefix) {
                return of(prefix.getValue(), prefix.getExponent());
        }

        /**
         * Creates a converter with a factor represented by specified base^exponent.
         * 
         * @param base
         * @param exponent
         * @return
         */
        static PowerOfIntConverter of(int base, int exponent) {
                return new PowerOfIntConverter(base, exponent);
        }
        
        /**
         * Creates a converter with a factor represented by specified base^exponent.
         * 
         * @param base
         * @param exponent
         * @return
         */
        static PowerOfIntConverter of(Number base, int exponent) {
                return new PowerOfIntConverter(base.intValue(), exponent);
        }

        protected PowerOfIntConverter(int base, int exponent) {
                if(base == 0) {
                        throw new IllegalArgumentException("base cannot be zero (because 0^0 is undefined)");
                }
                this.base = base;
                this.exponent = exponent;
                this.hashCode = Objects.hash(base, exponent);
                this.rationalFactor = calculateRationalNumberFactor();
        }

        public int getBase() {
                return base;
        }

        public int getExponent() {
                return exponent;
        }

        @Override
        public boolean isIdentity() {
                if( base == 1 ) {
                        return true; // 1^x = 1
                }
                return exponent == 0; // x^0 = 1, for any x!=0
                // [ahuber] 0^0 is undefined, but we guard against base==0 in the constructor,
                // and there is no composition, that changes the base
        }

        @Override
        protected boolean canReduceWith(AbstractConverter that) {
                if (that instanceof PowerOfIntConverter) {
                        return ((PowerOfIntConverter) that).base == this.base;
                }
                return that instanceof RationalConverter;
        }

        @Override
        protected AbstractConverter reduce(AbstractConverter that) {
                if (that instanceof PowerOfIntConverter) {
                        PowerOfIntConverter other = (PowerOfIntConverter) that;
                        if(this.base == other.base) { // always true due to guard above
                                return composeSameBaseNonIdentity(other);
                        } 
                }
                if (that instanceof RationalConverter) {
                        return (AbstractConverter) toRationalConverter().concatenate(that);
                }
                throw new IllegalStateException(String.format(
                                "%s.simpleCompose() not handled for converter %s", 
                                this, that));
        }

        @Override
        public AbstractConverter inverseWhenNotIdentity() {
                return new PowerOfIntConverter(base, -exponent);
        }

    @Override
    protected Number convertWhenNotIdentity(Number value) {
        return Calculator.of(rationalFactor)
                .multiply(value)
                .peek();
    }
    
        @Override
        public boolean equals(Object obj) {
                if (this == obj) {
                        return true;
                }
                if (obj instanceof UnitConverter) {
                        UnitConverter other = (UnitConverter) obj;
                        if(this.isIdentity() && other.isIdentity()) {
                                return true;
                        }
                }
                if (obj instanceof PowerOfIntConverter) {
                        PowerOfIntConverter other = (PowerOfIntConverter) obj;
                        return this.base == other.base && this.exponent == other.exponent;
                }
                return false;
        }

        @Override
        public final String transformationLiteral() {
                if(base<0) {
                        return String.format("x -> x * (%s)^%s", base, exponent);
                }
                return String.format("x -> x * %s^%s", base, exponent);
        }
        
    @Override
    public Number getValue() {
        return rationalFactor;
    }
    
        @Override
        public double getAsDouble() {
                return rationalFactor.doubleValue();
        }

        @Override
        public int compareTo(UnitConverter o) {
                if (this == o) {
                        return 0;
                }
                if(this.isIdentity() && o.isIdentity()) {
                        return 0;
                }
                if (o instanceof PowerOfIntConverter) {
                        PowerOfIntConverter other = (PowerOfIntConverter) o;
                        int c = Integer.compare(base, other.base);
                        if(c!=0) {
                                return c;
                        }
                        return Integer.compare(exponent, other.exponent);
                }
                return this.getClass().getName().compareTo(o.getClass().getName());
        }

        @Override
        public int hashCode() {
                return hashCode;
        }

        // -- HELPER
        
        private RationalNumber calculateRationalNumberFactor() {
        if(exponent==0) {
            return RationalNumber.ONE;
        }
        BigInteger bintFactor = BigInteger.valueOf(base).pow(Math.abs(exponent));
        if(exponent>0) {
            return RationalNumber.ofInteger(bintFactor);
        }
        return RationalNumber.of(BigInteger.ONE, bintFactor);
    }

        private PowerOfIntConverter composeSameBaseNonIdentity(PowerOfIntConverter other) {
                // no check for identity required
                return new PowerOfIntConverter(this.base, this.exponent + other.exponent);
        }

        public RationalConverter toRationalConverter() {
                return new RationalConverter(rationalFactor);
        }
}