/*
 * 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.ValueSupplier;

/**
 * <p>
 * This class represents a logarithmic converter of limited precision. Such converter is typically used to create logarithmic unit. For example:<code>
 * Unit<Dimensionless> BEL = Unit.ONE.transform(new LogConverter(10).inverse()); </code>
 *
 * @author <a href="mailto:jean-marie@dautelle.com">Jean-Marie Dautelle</a>
 * @author <a href="mailto:units@catmedia.us">Werner Keil</a>
 * @version 1.0.1, December 28, 2017
 * @since 1.0
 */
public final class LogConverter extends AbstractConverter implements ValueSupplier<String> { // implements
        // Immutable<String>
        // {

        /**
         * 
         */
        private static final long serialVersionUID = -7584688290961460870L;

        /**
         * Holds the logarithmic base.
         */
        private final double base;
        /**
         * Holds the natural logarithm of the base.
         */
        private final double logOfBase;

        /**
         * Returns a logarithmic converter having the specified base.
         *
         * @param base
         *          the logarithmic base (e.g. <code>Math.E</code> for the Natural Logarithm).
         */
        public LogConverter(double base) {
                this.base = base;
                this.logOfBase = Math.log(base);
        }

        /**
         * Returns the logarithmic base of this converter.
         *
         * @return the logarithmic base (e.g. <code>Math.E</code> for the Natural Logarithm).
         */
        public double getBase() {
                return base;
        }

        @Override
        public boolean isIdentity() {
                return false;
        }

        @Override
        protected boolean isSimpleCompositionWith(AbstractConverter that) {
                if(that instanceof ExpConverter) {
                        return ((ExpConverter)that).getBase() == base; // can compose with exp to identity, provided it has same base
                }
                return false;
        }

        @Override
        protected AbstractConverter simpleCompose(AbstractConverter that) {
                return AbstractConverter.IDENTITY;
        }

        @Override
        public AbstractConverter inverseWhenNotIdentity() {
                return new ExpConverter(base);
        }

        @Override
        public final String transformationLiteral() {
                if (base == Math.E) {
                        return "x -> ln(x)";
                } else {
                        return String.format("x -> log(base=%s, x)", base);
                }
        }
        
        @Override
        public boolean equals(Object obj) {
                if (this == obj) {
                        return true;
                }
                if (obj instanceof LogConverter) {
                        LogConverter that = (LogConverter) obj;
                        return Objects.equals(base, that.base);
                }
                return false;
        }

        @Override
        public int hashCode() {
                return Objects.hash(base);
        }

        @Override
        public double convertWhenNotIdentity(double amount) {
                return Math.log(amount) / logOfBase;
        }

        @Override
        public BigDecimal convertWhenNotIdentity(BigDecimal value, MathContext ctx) throws ArithmeticException {
                return BigDecimal.valueOf(convert(value.doubleValue())); // Reverts to
                // double
                // conversion.
        }

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

        @Override
        public String getValue() {
                return toString();
        }

        @Override
        public int compareTo(UnitConverter o) {
                if (this == o) {
                        return 0;
                }
                if (o instanceof ValueSupplier) {
                        return getValue().compareTo(String.valueOf(((ValueSupplier<?>) o).getValue()));
                }
                return -1;
        }
}