/*
 * Java Genetic Algorithm Library (jenetics-8.1.0).
 * Copyright (c) 2007-2024 Franz Wilhelmstötter
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Author:
 *    Franz Wilhelmstötter (franz.wilhelmstoetter@gmail.com)
 */
package io.jenetics;

import static io.jenetics.internal.util.Hashes.hash;
import static io.jenetics.util.RandomRegistry.random;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.Serial;
import java.io.Serializable;

import io.jenetics.util.DoubleRange;
import io.jenetics.util.ISeq;
import io.jenetics.util.IntRange;
import io.jenetics.util.MSeq;
import io.jenetics.util.Mean;

/**
 * Implementation of the NumericGene which holds a 64-bit floating point number.
 *
 * <p>This is a <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/doc-files/ValueBased.html">
 * value-based</a> class; use of identity-sensitive operations (including
 * reference equality ({@code ==}), identity hash code, or synchronization) on
 * instances of {@code DoubleGene} may have unpredictable results and should
 * be avoided.
 *
 * @see DoubleChromosome
 *
 * @implNote
 * This class is immutable and thread-safe.
 *
 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
 * @since 1.6
 * @version 6.0
 */
public final class DoubleGene
        implements
                NumericGene<Double, DoubleGene>,
                Mean<DoubleGene>,
                Comparable<DoubleGene>,
                Serializable
{

        @Serial
        private static final long serialVersionUID = 2L;

        private final double _allele;
        private final double _min;
        private final double _max;

        /**
         * Create a new random {@code DoubleGene} with the given value and the
         * given range. If the {@code value} isn't within the interval [min, max),
         * no exception is thrown. In this case the method
         * {@link DoubleGene#isValid()} returns {@code false}.
         *
         * @param allele the value of the gene.
         * @param min the minimal valid value of this gene (inclusively).
         * @param max the maximal valid value of this gene (exclusively).
         */
        private DoubleGene(final double allele, final double min, final double max) {
                _allele = allele;
                _min = min;
                _max = max;
        }

        @Override
        public Double allele() {
                return _allele;
        }

        @Override
        public Double min() {
                return _min;
        }

        @Override
        public Double max() {
                return _max;
        }

        /**
         * Return the range of {@code this} gene.
         *
         * @since 4.4
         *
         * @return the range of {@code this} gene
         */
        public DoubleRange range() {
                return DoubleRange.of(_min, _max);
        }

        @Override
        public byte byteValue() {
                return (byte)_allele;
        }

        @Override
        public short shortValue() {
                return (short)_allele;
        }

        @Override
        public int intValue() {
                return (int)_allele;
        }

        @Override
        public long longValue() {
                return (long)_allele;
        }

        @Override
        public float floatValue() {
                return (float)_allele;
        }

        @Override
        public double doubleValue() {
                 return _allele;
        }

        @Override
        public boolean isValid() {
                return
                        Double.isFinite(_allele) &&
                        Double.isFinite(_min) &&
                        Double.isFinite(_max) &&
                        Double.compare(_allele, _min) >= 0 &&
                        Double.compare(_allele, _max) < 0;
        }

        @Override
        public int compareTo(final DoubleGene other) {
                return Double.compare(_allele, other._allele);
        }

        @Override
        public DoubleGene mean(final DoubleGene that) {
                // (a - a/2) + b/2
                // https://hal.archives-ouvertes.fr/hal-00576641v1/document
                return of((_allele - _allele/2.0) + that._allele/2.0, _min, _max);
        }

        /**
         * Create a new gene from the given {@code value} and the gene context.
         *
         * @since 5.0
         * @param allele the value of the new gene.
         * @return a new gene with the given value.
         */
        public DoubleGene newInstance(final double allele) {
                return DoubleGene.of(allele, _min, _max);
        }

        @Override
        public DoubleGene newInstance(final Double allele) {
                return of(allele, _min, _max);
        }

        @Override
        public DoubleGene newInstance(final Number allele) {
                return of(allele.doubleValue(), _min, _max);
        }

        @Override
        public DoubleGene newInstance() {
                return of(random().nextDouble(_min, _max), _min, _max);
        }

        @Override
        public int hashCode() {
                return hash(_allele, hash(_min, hash(_max)));
        }

        @Override
        public boolean equals(final Object obj) {
                return obj == this ||
                        obj instanceof DoubleGene other &&
                        Double.compare(other._allele, _allele) == 0 &&
                        Double.compare(other._min, _min) == 0 &&
                        Double.compare(other._max, _max) == 0;
        }

        @Override
        public String toString() {
                return String.format("[%s]", _allele);
        }


        /* *************************************************************************
         * Static factory methods.
         * ************************************************************************/

        /**
         * Create a new random {@code DoubleGene} with the given value and the
         * given range. If the {@code value} isn't within the interval [min, max),
         * no exception is thrown. In this case the method
         * {@link DoubleGene#isValid()} returns {@code false}.
         *
         * @param allele the value of the gene.
         * @param min the minimal valid value of this gene (inclusively).
         * @param max the maximal valid value of this gene (exclusively).
         * @return a new {@code DoubleGene} with the given parameter
         */
        public static DoubleGene of(
                final double allele,
                final double min,
                final double max
        ) {
                return new DoubleGene(allele, min, max);
        }

        /**
         * Create a new random {@code DoubleGene} with the given value and the
         * given range. If the {@code value} isn't within the interval
         * {@code [min, max)}, no exception is thrown. In this case the method
         * {@link DoubleGene#isValid()} returns {@code false}.
         *
         * @since 3.2
         *
         * @param allele the value of the gene
         * @param range the double range to use
         * @return a new random {@code DoubleGene}
         * @throws NullPointerException if the given {@code range} is {@code null}
         */
        public static DoubleGene of(final double allele, final DoubleRange range) {
                return of(allele, range.min(), range.max());
        }

        /**
         * Create a new random {@code DoubleGene}. It is guaranteed that the value
         * of the {@code DoubleGene} lies in the interval {@code [min, max)}.
         *
         * @param min the minimal valid value of this gene (inclusively)
         * @param max the maximal valid value of this gene (exclusively)
         * @return a new {@code DoubleGene} with the given parameter
         * @throws IllegalArgumentException if {@code min} is not finite,
         *         or {@code max} is not finite, or {@code min}
         *         is greater than or equal to {@code max}
         */
        public static DoubleGene of(final double min, final double max) {
                return of(random().nextDouble(min, max), min, max);
        }

        /**
         * Create a new random {@code DoubleGene}. It is guaranteed that the value
         * of the {@code DoubleGene} lies in the interval {@code [min, max)}.
         *
         * @since 3.2
         *
         * @param range the double range to use
         * @return a new {@code DoubleGene} with the given parameter
         * @throws NullPointerException if the given {@code range} is {@code null}
         * @throws IllegalArgumentException if {@code min} is not finite,
         *         or {@code max} is not finite, or {@code min}
         *         is greater than or equal to {@code max}
         */
        public static DoubleGene of(final DoubleRange range) {
                return of(range.min(), range.max());
        }

        static ISeq<DoubleGene> seq(
                final double min,
                final double max,
                final IntRange lengthRange
        ) {
                final var random = random();
                final var length = random.nextInt(lengthRange.min(), lengthRange.max());

                return MSeq.<DoubleGene>ofLength(length)
                        .fill(() -> new DoubleGene(random.nextDouble(min, max), min, max))
                        .toISeq();
        }


        /* *************************************************************************
         *  Java object serialization
         * ************************************************************************/

        @Serial
        private Object writeReplace() {
                return new SerialProxy(SerialProxy.DOUBLE_GENE, this);
        }

        @Serial
        private void readObject(final ObjectInputStream stream)
                throws InvalidObjectException
        {
                throw new InvalidObjectException("Serialization proxy required.");
        }

        void write(final DataOutput out) throws IOException {
                out.writeDouble(_allele);
                out.writeDouble(_min);
                out.writeDouble(_max);
        }

        static DoubleGene read(final DataInput in) throws IOException {
                return of(in.readDouble(), in.readDouble(), in.readDouble());
        }

}