/*
 * Units of Measurement Reference Implementation
 * Copyright (c) 2005-2018, 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.BigDecimal;
import java.math.MathContext;
import java.util.Objects;

import javax.measure.UnitConverter;

import tech.units.indriya.AbstractConverter;
import tech.uom.lib.common.function.IntExponentSupplier;

/**
 * This class represents a converter multiplying numeric values by a factor of
 * Pi to the power of an integer exponent (π^exponent).
 * @author Andi Huber
 * @author Werner Keil
 * @version 1.1, May 10, 2018
 * @since 2.0
 */
public final class PowerOfPiConverter extends AbstractConverter 
 implements IntExponentSupplier {
        private static final long serialVersionUID = 5000593326722785126L;
        
        private final int exponent;
        private final int hashCode;
        private final double doubleFactor; // for double calculus only

        /**
         * Creates a converter with the specified exponent.
         * 
         * @param exponent
         *            the exponent for the factor π^exponent.
         */
        public static PowerOfPiConverter of(int exponent) {
                return new PowerOfPiConverter(exponent);
        }

        protected PowerOfPiConverter(int exponent) {
                this.exponent = exponent;
                this.doubleFactor =  Math.pow(Math.PI, exponent);
                this.hashCode = Objects.hash(exponent);
        }

        public int getExponent() {
                return exponent;
        }

        @Override
        public boolean isIdentity() {
                return exponent == 0; // x^0 = 1, for any x!=0
        }

        @Override
        public boolean isLinear() {
                return true;
        }

        @Override
        public AbstractConverter inverseWhenNotIdentity() {
                return new PowerOfPiConverter(-exponent);
        }

        @Override
        public BigDecimal convertWhenNotIdentity(BigDecimal value, MathContext ctx) throws ArithmeticException {
                int nbrDigits = ctx.getPrecision();
                if (nbrDigits == 0) {
                        throw new ArithmeticException("Pi multiplication with unlimited precision");
                }
                BigDecimal pi = Constants.Pi.ofNumDigits(nbrDigits);
                return pi.pow(exponent, ctx).multiply(value);
        }

        @Override
        public double convertWhenNotIdentity(double value) {
                //[ahuber] multiplication is probably non-critical regarding preservation of precision
                return value * doubleFactor;
        }

        @Override
        protected boolean isSimpleCompositionWith(AbstractConverter that) {
                return that instanceof PowerOfPiConverter;
        }

        @Override
        protected AbstractConverter simpleCompose(AbstractConverter that) {
                return new PowerOfPiConverter(this.exponent + ((PowerOfPiConverter)that).exponent);
        }

        @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 PowerOfPiConverter) {
                        PowerOfPiConverter other = (PowerOfPiConverter) obj;
                        return this.exponent == other.exponent;
                }
                return false;
        }

        @Override
        public final String transformationLiteral() {
                return String.format("x -> x * π^%s", exponent);
        }

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

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

}