/*
 * Java Genetic Algorithm Library (jenetics-8.2.0).
 * Copyright (c) 2007-2025 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.internal.util.SerialIO.readInt;
import static io.jenetics.internal.util.SerialIO.writeInt;
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.ISeq;
import io.jenetics.util.IntRange;
import io.jenetics.util.MSeq;
import io.jenetics.util.Mean;

/**
 * NumericGene implementation which holds a 32-bit integer 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 IntegerGene} may have unpredictable results and should
 * be avoided.
 *
 * @see IntegerChromosome
 *
 * @implNote
 * This class is immutable and thread-safe.
 *
 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
 * @since 2.0
 * @version 7.0
 */
public final class IntegerGene
        implements
                NumericGene<Integer, IntegerGene>,
                Mean<IntegerGene>,
                Comparable<IntegerGene>,
                Serializable
{

        @Serial
        private static final long serialVersionUID = 2L;

        private final int _allele;
        private final int _min;
        private final int _max;

        /**
         * Create a new random {@code IntegerGene} 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 IntegerGene#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 IntegerGene(final int allele, final int min, final int max) {
                _allele = allele;
                _min = min;
                _max = max;
        }

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

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

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

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

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

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

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

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

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

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

        @Override
        public boolean isValid() {
                return _allele >= _min && _allele < _max;
        }

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

        @Override
        public IntegerGene mean(final IntegerGene that) {
                final int x = that._allele;
                final int y = _allele;

                // http://aggregate.org/MAGIC/#Average%20of%20Integers
                return IntegerGene.of((x&y) + ((x^y) >> 1), _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 IntegerGene newInstance(final int allele) {
                return IntegerGene.of(allele, _min, _max);
        }

        @Override
        public IntegerGene newInstance(final Integer allele) {
                return IntegerGene.of(allele, _min, _max);
        }

        @Override
        public IntegerGene newInstance(final Number allele) {
                final int value = allele instanceof Double || allele instanceof Float
                        ? (int)Math.round(allele.doubleValue())
                        : allele.intValue();

                return IntegerGene.of(value, _min, _max);
        }

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

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

        @Override
        public boolean equals(final Object obj) {
                return obj instanceof IntegerGene other &&
                        other._allele == _allele &&
                        other._min == _min &&
                        other._max == _max;
        }

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

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

        /**
         * Create a new random {@code IntegerGene} 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 IntegerGene#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 IntegerGene} with the given {@code value}
         */
        public static IntegerGene of(final int allele, final int min, final int max) {
                return new IntegerGene(allele, min, max);
        }

        /**
         * Create a new random {@code IntegerGene} 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 IntegerGene#isValid()} returns {@code false}.
         *
         * @since 3.2
         *
         * @param allele the value of the gene.
         * @param range the integer range to use
         * @return a new {@code IntegerGene} with the give {@code value}
         * @throws NullPointerException if the given {@code range} is {@code null}.
         */
        public static IntegerGene of(final int allele, final IntRange range) {
                return IntegerGene.of(allele, range.min(), range.max());
        }

        /**
         * Create a new random {@code IntegerGene}. It is guaranteed that the value of
         * the {@code IntegerGene} 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 random {@code IntegerGene}
         * @throws IllegalArgumentException if {@code max} is greater than
         *         or equal to {@code min}
         */
        public static IntegerGene of(final int min, final int max) {
                return of(random().nextInt(min, max), min, max);
        }

        /**
         * Create a new random {@code IntegerGene}. It is guaranteed that the value of
         * the {@code IntegerGene} lies in the interval {@code [min, max)}.
         *
         * @since 3.2
         *
         * @param range the integer range to use
         * @return a new random {@code IntegerGene}
         * @throws NullPointerException if the given {@code range} is {@code null}.
         * @throws IllegalArgumentException if {@code max} is greater than
         *         or equal to {@code min}
         */
        public static IntegerGene of(final IntRange range) {
                return of(random().nextInt(range.min(), range.max()), range);
        }

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

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


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

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

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

        void write(final DataOutput out) throws IOException {
                writeInt(_allele, out);
                writeInt(_min, out);
                writeInt(_max, out);
        }

        static IntegerGene read(final DataInput in) throws IOException {
                return of(readInt(in), readInt(in), readInt(in));
        }

}