/*
 * Java Genetic Algorithm Library (jenetics-7.2.0).
 * Copyright (c) 2007-2023 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.engine;

import static java.lang.String.format;
import static java.util.Objects.requireNonNull;
import static io.jenetics.internal.util.Requires.probability;
import static io.jenetics.internal.util.SerialIO.readInt;
import static io.jenetics.internal.util.SerialIO.readLong;
import static io.jenetics.internal.util.SerialIO.writeInt;
import static io.jenetics.internal.util.SerialIO.writeLong;

import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInput;
import java.io.ObjectInputStream;
import java.io.ObjectOutput;
import java.io.Serial;
import java.io.Serializable;
import java.util.Objects;
import java.util.stream.Stream;

import io.jenetics.Alterer;
import io.jenetics.Gene;
import io.jenetics.Mutator;
import io.jenetics.Selector;
import io.jenetics.SinglePointCrossover;
import io.jenetics.TournamentSelector;
import io.jenetics.internal.util.Requires;

/**
 * This class collects the parameters which control the behavior of the
 * evolution process. This doesn't include the parameters for the
 * <em>technical</em> execution like the used execution service.
 *
 * @see Engine
 * @see Engine.Builder
 *
 * @param <G> the gene type
 * @param <C> the fitness function result type
 *
 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
 * @version 5.2
 * @since 5.2
 */
public final class EvolutionParams<
        G extends Gene<?, G>,
        C extends Comparable<? super C>
>
        implements Serializable
{

        @Serial
        private static final long serialVersionUID = 1L;

        private final Selector<G, C> _survivorsSelector;
        private final Selector<G, C> _offspringSelector;
        private final Alterer<G, C> _alterer;
        private final int _populationSize;
        private final double _offspringFraction;
        private final long _maximalPhenotypeAge;

        private EvolutionParams(
                final Selector<G, C> survivorsSelector,
                final Selector<G, C> offspringSelector,
                final Alterer<G, C> alterer,
                final int populationSize,
                final double offspringFraction,
                final long maximalPhenotypeAge
        ) {
                _survivorsSelector = requireNonNull(survivorsSelector);
                _offspringSelector = requireNonNull(offspringSelector);
                _alterer = requireNonNull(alterer);
                _populationSize = Requires.positive(populationSize);
                _offspringFraction = Requires.probability(offspringFraction);
                _maximalPhenotypeAge = Requires.positive(maximalPhenotypeAge);
        }


        /**
         * Return the used survivor {@link Selector} of the GA.
         *
         * @return the used survivor {@link Selector} of the GA.
         */
        public Selector<G, C> survivorsSelector() {
                return _survivorsSelector;
        }

        /**
         * Return the used offspring {@link Selector} of the GA.
         *
         * @return the used offspring {@link Selector} of the GA.
         */
        public Selector<G, C> offspringSelector() {
                return _offspringSelector;
        }

        /**
         * Return the used {@link Alterer} of the GA.
         *
         * @return the used {@link Alterer} of the GA.
         */
        public Alterer<G, C> alterer() {
                return _alterer;
        }


        /**
         * Return the population size.
         *
         * @return the population size
         */
        public int populationSize() {
                return _populationSize;
        }

        /**
         * Return the offspring fraction.
         *
         * @return the offspring fraction.
         */
        public double offspringFraction() {
                return _offspringFraction;
        }

        /**
         * Return the maximal allowed phenotype age.
         *
         * @return the maximal allowed phenotype age
         */
        public long maximalPhenotypeAge() {
                return _maximalPhenotypeAge;
        }


        /* *************************************************************************
         * Derived properties.
         **************************************************************************/

        /**
         * Return the number of offspring. <em>This is a derived property.</em>
         *
         * @return the offspring count.
         */
        public int offspringSize() {
                return (int)Math.rint(_populationSize*_offspringFraction);
        }

        /**
         * Return the number of survivors. <em>This is a derived property.</em>
         *
         * @return the number of survivors
         */
        public int survivorsSize() {
                return _populationSize - offspringSize();
        }

        /**
         * Return a new builder object, initialized with {@code this} parameters.
         *
         * @return a new pre-filled builder object
         */
        public EvolutionParams.Builder<G, C> toBuilder() {
                return EvolutionParams.<G, C>builder()
                        .survivorsSelector(survivorsSelector())
                        .offspringSelector(offspringSelector())
                        .alterers(alterer())
                        .populationSize(populationSize())
                        .offspringFraction(offspringFraction())
                        .maximalPhenotypeAge(maximalPhenotypeAge());
        }

        /**
         * Create a new evolution parameter builder.
         *
         * @param <G> the gene type
         * @param <C> the fitness function result type
         * @return a new parameter builder
         */
        public static  <G extends Gene<?, G>, C extends Comparable<? super C>>
        Builder<G, C> builder() {
                return new Builder<>();
        }


        /* *************************************************************************
         * Params builder
         **************************************************************************/

        /**
         * Builder class for the evolution parameter.
         *
         * @param <G> the gene type
         * @param <C> the fitness function result type
         */
        public static final class Builder<
                G extends Gene<?, G>,
                C extends Comparable<? super C>
        > {

                private Selector<G, C> _survivorsSelector = new TournamentSelector<>(3);
                private Selector<G, C> _offspringSelector = new TournamentSelector<>(3);
                private Alterer<G, C> _alterer = Alterer.of(
                        new SinglePointCrossover<G, C>(0.2),
                        new Mutator<>(0.15)
                );
                private int _populationSize = 50;
                private double _offspringFraction = 0.6;
                private long _maximalPhenotypeAge = 70;


                private Builder() {
                }

                public Builder<G, C> evolutionParams(final EvolutionParams<G, C> params) {
                        survivorsSelector(params.survivorsSelector());
                        offspringSelector(params.offspringSelector());
                        alterers(params.alterer());
                        populationSize(params.populationSize());
                        offspringFraction(params.offspringFraction());
                        maximalPhenotypeAge(params.maximalPhenotypeAge());
                        return this;
                }

                /**
                 * The selector used for selecting the offspring population. <i>Default
                 * values is set to {@code TournamentSelector<>(3)}.</i>
                 *
                 * @param selector used for selecting the offspring population
                 * @return {@code this} builder, for command chaining
                 */
                public Builder<G, C> offspringSelector(
                        final Selector<G, C> selector
                ) {
                        _offspringSelector = requireNonNull(selector);
                        return this;
                }

                /**
                 * The selector used for selecting the survivor population. <i>Default
                 * values is set to {@code TournamentSelector<>(3)}.</i>
                 *
                 * @param selector used for selecting survivor population
                 * @return {@code this} builder, for command chaining
                 */
                public Builder<G, C> survivorsSelector(
                        final Selector<G, C> selector
                ) {
                        _survivorsSelector = requireNonNull(selector);
                        return this;
                }

                /**
                 * The selector used for selecting the survivors and offspring
                 * population. <i>Default values is set to
                 * {@code TournamentSelector<>(3)}.</i>
                 *
                 * @param selector used for selecting survivors and offspring population
                 * @return {@code this} builder, for command chaining
                 */
                public Builder<G, C> selector(final Selector<G, C> selector) {
                        _offspringSelector = requireNonNull(selector);
                        _survivorsSelector = requireNonNull(selector);
                        return this;
                }

                /**
                 * The alterers used for alter the offspring population. <i>Default
                 * values is set to {@code new SinglePointCrossover<>(0.2)} followed by
                 * {@code new Mutator<>(0.15)}.</i>
                 *
                 * @param first the first alterer used for alter the offspring
                 *        population
                 * @param rest the rest of the alterers used for alter the offspring
                 *        population
                 * @return {@code this} builder, for command chaining
                 * @throws java.lang.NullPointerException if one of the alterers is
                 *         {@code null}.
                 */
                @SafeVarargs
                public final Builder<G, C> alterers(
                        final Alterer<G, C> first,
                        final Alterer<G, C>... rest
                ) {
                        requireNonNull(first);
                        Stream.of(rest).forEach(Objects::requireNonNull);

                        _alterer = rest.length == 0
                                ? first
                                : Alterer.of(rest).compose(first);

                        return this;
                }

                /**
                 * The number of individuals which form the population. <i>Default
                 * values is set to {@code 50}.</i>
                 *
                 * @param size the number of individuals of a population
                 * @return {@code this} builder, for command chaining
                 * @throws IllegalArgumentException if {@code size < 1}
                 */
                public Builder<G, C> populationSize(final int size) {
                        if (size < 1) {
                                throw new IllegalArgumentException(format(
                                        "Population size must be greater than zero, but was %s.",
                                        size
                                ));
                        }

                        _populationSize = size;
                        return this;
                }


                /**
                 * The offspring fraction.
                 *
                 * @param fraction the offspring fraction
                 * @return {@code this} builder, for command chaining
                 * @throws IllegalArgumentException if the fraction is not within the
                 *         range [0, 1].
                 */
                public Builder<G, C> offspringFraction(final double fraction) {
                        _offspringFraction = probability(fraction);
                        return this;
                }

                /**
                 * The maximal allowed age of a phenotype. <i>Default values is set to
                 * {@code 70}.</i>
                 *
                 * @param age the maximal phenotype age
                 * @return {@code this} builder, for command chaining
                 * @throws IllegalArgumentException if {@code age < 1}
                 */
                public Builder<G, C> maximalPhenotypeAge(final long age) {
                        if (age < 1) {
                                throw new IllegalArgumentException(format(
                                        "Phenotype age must be greater than one, but was %s.", age
                                ));
                        }
                        _maximalPhenotypeAge = age;
                        return this;
                }

                /**
                 * Builds a new {@code EvolutionParams} instance from the set properties.
                 *
                 * @return a new {@code EvolutionParams} instance from the set properties
                 */
                public EvolutionParams<G, C> build() {
                        return new EvolutionParams<>(
                                _survivorsSelector,
                                _offspringSelector,
                                _alterer,
                                _populationSize,
                                _offspringFraction,
                                _maximalPhenotypeAge
                        );
                }


                /* *********************************************************************
                 * Current properties
                 ***********************************************************************/

                /**
                 * Return the used {@link Alterer} of the GA.
                 *
                 * @return the used {@link Alterer} of the GA.
                 */
                public Alterer<G, C> alterer() {
                        return _alterer;
                }


                /**
                 * Return the maximal allowed phenotype age.
                 *
                 * @return the maximal allowed phenotype age
                 */
                public long maximalPhenotypeAge() {
                        return _maximalPhenotypeAge;
                }

                /**
                 * Return the used offspring {@link Selector} of the GA.
                 *
                 * @return the used offspring {@link Selector} of the GA.
                 */
                public Selector<G, C> offspringSelector() {
                        return _offspringSelector;
                }

                /**
                 * Return the used survivor {@link Selector} of the GA.
                 *
                 * @return the used survivor {@link Selector} of the GA.
                 */
                public Selector<G, C> survivorsSelector() {
                        return _survivorsSelector;
                }

                /**
                 * Return the number of individuals of a population.
                 *
                 * @return the number of individuals of a population
                 */
                public int populationSize() {
                        return _populationSize;
                }

                /**
                 * Return the offspring fraction.
                 *
                 * @return the offspring fraction.
                 */
                public double offspringFraction() {
                        return _offspringFraction;
                }

                /* *************************************************************************
                 * Derived properties.
                 **************************************************************************/

                /**
                 * Return the number of offspring. <em>This is a derived property.</em>
                 *
                 * @return the offspring count.
                 */
                public int offspringSize() {
                        return (int)Math.round(_populationSize*_offspringFraction);
                }

                /**
                 * Return the number of survivors. <em>This is a derived property.</em>
                 *
                 * @return the number of survivors
                 */
                public int survivorsSize() {
                        return _populationSize - offspringSize();
                }

        }

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

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

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

        void write(final ObjectOutput out) throws IOException {
                out.writeObject(survivorsSelector());
                out.writeObject(offspringSelector());
                out.writeObject(alterer());
                writeInt(populationSize(), out);
                out.writeDouble(offspringFraction());
                writeLong(maximalPhenotypeAge(), out);
        }

        @SuppressWarnings({"unchecked", "rawtypes"})
        static EvolutionParams read(final ObjectInput in)
                throws IOException, ClassNotFoundException
        {
                return new EvolutionParams(
                        (Selector)in.readObject(),
                        (Selector)in.readObject(),
                        (Alterer)in.readObject(),
                        readInt(in),
                        in.readDouble(),
                        readLong(in)
                );
        }

}