/*
 * 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.prog;

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

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.function.Function;
import java.util.function.Predicate;

import io.jenetics.util.ISeq;
import io.jenetics.util.MSeq;

import io.jenetics.ext.AbstractTreeChromosome;
import io.jenetics.ext.util.FlatTreeNode;
import io.jenetics.ext.util.Tree;
import io.jenetics.ext.util.TreeNode;

import io.jenetics.prog.op.Op;
import io.jenetics.prog.op.Program;

/**
 * Holds the nodes of the operation tree.
 *
 * {@snippet lang="java":
 * final int depth = 6;
 * final ISeq<Op<Double>> operations = ISeq.of(null); // @replace substring='null' replacement="..."
 * final ISeq<Op<Double>> terminals = ISeq.of(null); // @replace substring='null' replacement="..."
 * final ProgramChromosome<Double> ch = ProgramChromosome.of(
 *     depth,
 *     // If the program has more than 200 nodes, it is marked as "invalid".
 *     ch -> ch.length() <= 200,
 *     operations,
 *     terminals
 * );
 * }
 *
 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
 * @version 4.1
 * @since 3.9
 */
public class ProgramChromosome<A>
        extends AbstractTreeChromosome<Op<A>, ProgramGene<A>>
        implements Function<A[], A>, Serializable
{

        @Serial
        private static final long serialVersionUID = 2L;

        private final Predicate<? super ProgramChromosome<A>> _validator;
        private final ISeq<Op<A>> _operations;
        private final ISeq<Op<A>> _terminals;

        /**
         * Create a new program chromosome from the given program genes. This
         * constructor assumes that the given {@code program} is valid. Since the
         * program validation is quite expensive, the validity check is skipped in
         * this constructor.
         *
         * @param program the program. During the program evolution, newly created
         *        program trees have the same <em>depth</em> than this tree.
         * @param validator the chromosome validator. A typical validator would
         *        check the size of the tree and if the tree is too large, mark it
         *        at <em>invalid</em>. The <em>validator</em> may be {@code null}.
         * @param operations the allowed non-terminal operations
         * @param terminals the allowed terminal operations
         * @throws NullPointerException if one of the given arguments is {@code null}
         * @throws IllegalArgumentException if either the {@code operations} or
         *         {@code terminals} sequence is empty
         */
        protected ProgramChromosome(
                final ISeq<ProgramGene<A>> program,
                final Predicate<? super ProgramChromosome<A>> validator,
                final ISeq<? extends Op<A>> operations,
                final ISeq<? extends Op<A>> terminals
        ) {
                super(program);
                _validator = requireNonNull(validator);
                _operations = requireNonNull(ISeq.upcast(operations));
                _terminals = requireNonNull(ISeq.upcast(terminals));

                if (operations.isEmpty()) {
                        throw new IllegalArgumentException("No operations given.");
                }
                if (terminals.isEmpty()) {
                        throw new IllegalArgumentException("No terminals given");
                }
        }

        /**
         * Return the allowed operations.
         *
         * @since 5.0
         *
         * @return the allowed operations
         */
        public ISeq<Op<A>> operations() {
                return _operations;
        }

        /**
         * Return the allowed terminal operations.
         *
         * @since 5.0
         *
         * @return the allowed terminal operations
         */
        public ISeq<Op<A>> terminals() {
                return _terminals;
        }

        @Override
        public boolean isValid() {
                if (_valid == null) {
                        _valid = _validator.test(this);
                }

                return _valid;
        }

        private boolean isSuperValid() {
                return super.isValid();
        }

        /**
         * Evaluates the root node of this chromosome.
         *
         * @see ProgramGene#apply(Object[])
         * @see ProgramChromosome#eval(Object[])
         *
         * @param args the input variables
         * @return the evaluated value
         * @throws NullPointerException if the given variable array is {@code null}
         */
        @Override
        public A apply(final A[] args) {
                return root().apply(args);
        }

        /**
         * Evaluates the root node of this chromosome.
         *
         * @see ProgramGene#eval(Object[])
         * @see ProgramChromosome#apply(Object[])
         *
         * @param args the function arguments
         * @return the evaluated value
         * @throws NullPointerException if the given variable array is {@code null}
         */
        @SafeVarargs
        public final A eval(final A... args) {
                return root().eval(args);
        }

        @Override
        public ProgramChromosome<A> newInstance(final ISeq<ProgramGene<A>> genes) {
                return create(genes, _validator, _operations, _terminals);
        }

        @Override
        public ProgramChromosome<A> newInstance() {
                return create(root().depth(), _validator, _operations, _terminals);
        }

        /**
         * Create a new chromosome from the given operation tree (program).
         *
         * @param program the operation tree
         * @param validator the chromosome validator. A typical validator would
         *        check the size of the tree and if the tree is too large, mark it
         *        at <em>invalid</em>. The <em>validator</em> may be {@code null}.
         * @param operations the allowed non-terminal operations
         * @param terminals the allowed terminal operations
         * @param <A> the operation type
         * @return a new chromosome from the given operation tree
         * @throws NullPointerException if one of the given arguments is {@code null}
         * @throws IllegalArgumentException if the given operation tree is invalid,
         *         which means there is at least one node where the operation arity
         *         and the node child count differ.
         */
        public static <A> ProgramChromosome<A> of(
                final Tree<? extends Op<A>, ?> program,
                final Predicate<? super ProgramChromosome<A>> validator,
                final ISeq<? extends Op<A>> operations,
                final ISeq<? extends Op<A>> terminals
        ) {
                Program.check(program);
                checkOperations(operations);
                checkTerminals(terminals);

                return create(program, validator, operations, terminals);
        }

        // Create the chromosomes without checks.
        private static <A> ProgramChromosome<A> create(
                final Tree<? extends Op<A>, ?> program,
                final Predicate<? super ProgramChromosome<A>> validator,
                final ISeq<? extends Op<A>> operations,
                final ISeq<? extends Op<A>> terminals
        ) {
                final ISeq<ProgramGene<A>> genes = FlatTreeNode.ofTree(program).stream()
                        .map(n -> new ProgramGene<>(
                                n.value(), n.childOffset(), operations, terminals))
                        .collect(ISeq.toISeq());

                return new ProgramChromosome<>(genes, validator, operations, terminals);
        }

        private static void checkOperations(final ISeq<? extends Op<?>> operations) {
                final ISeq<?> terminals = operations.stream()
                        .filter(Op::isTerminal)
                        .collect(ISeq.toISeq());

                if (!terminals.isEmpty()) {
                        throw new IllegalArgumentException(format(
                                "Operations must not contain terminals: %s",
                                terminals.toString(",")
                        ));
                }
        }

        private static void checkTerminals(final ISeq<? extends Op<?>> terminals) {
                final ISeq<?> operations = terminals.stream()
                        .filter(op -> !op.isTerminal())
                        .collect(ISeq.toISeq());

                if (!operations.isEmpty()) {
                        throw new IllegalArgumentException(format(
                                "Terminals must not contain operations: %s",
                                operations.toString(",")
                        ));
                }
        }

        /**
         * Create a new chromosome from the given operation tree (program).
         *
         * @param program the operation tree
         * @param operations the allowed non-terminal operations
         * @param terminals the allowed terminal operations
         * @param <A> the operation type
         * @return a new chromosome from the given operation tree
         * @throws NullPointerException if one of the given arguments is {@code null}
         * @throws IllegalArgumentException if the given operation tree is invalid,
         *         which means there is at least one node where the operation arity
         *         and the node child count differ.
         */
        public static <A> ProgramChromosome<A> of(
                final Tree<? extends Op<A>, ?> program,
                final ISeq<? extends Op<A>> operations,
                final ISeq<? extends Op<A>> terminals
        ) {
                return of(
                        program,
                        (Predicate<? super ProgramChromosome<A>> & Serializable)ProgramChromosome::isSuperValid,
                        operations,
                        terminals
                );
        }

        /**
         * Create a new program chromosome with the defined depth. This method will
         * create a <em>full</em> program tree.
         *
         * @param depth the depth of the created program tree
         * @param validator the chromosome validator. A typical validator would
         *        check the size of the tree and if the tree is too large, mark it
         *        at <em>invalid</em>. The <em>validator</em> may be {@code null}.
         * @param operations the allowed non-terminal operations
         * @param terminals the allowed terminal operations
         * @param <A> the operation type
         * @return a new program chromosome from the given (flattened) program tree
         * @throws NullPointerException if one of the parameters is {@code null}
         * @throws IllegalArgumentException if the {@code depth} is smaller than zero
         */
        public static <A> ProgramChromosome<A> of(
                final int depth,
                final Predicate<? super ProgramChromosome<A>> validator,
                final ISeq<? extends Op<A>> operations,
                final ISeq<? extends Op<A>> terminals
        ) {
                checkOperations(operations);
                checkTerminals(terminals);

                return create(depth, validator, operations, terminals);
        }

        private static <A> ProgramChromosome<A> create(
                final int depth,
                final Predicate<? super ProgramChromosome<A>> validator,
                final ISeq<? extends Op<A>> operations,
                final ISeq<? extends Op<A>> terminals
        ) {
                return create(
                        Program.of(depth, operations, terminals),
                        validator,
                        operations,
                        terminals
                );
        }

        /**
         * Create a new program chromosome with the defined depth. This method will
         * create a <em>full</em> program tree.
         *
         * @param depth the depth of the created (full) program tree
         * @param operations the allowed non-terminal operations
         * @param terminals the allowed terminal operations
         * @param <A> the operation type
         * @return a new program chromosome from the given (flattened) program tree
         * @throws NullPointerException if one of the parameters is {@code null}
         * @throws IllegalArgumentException if the {@code depth} is smaller than zero
         */
        public static <A> ProgramChromosome<A> of(
                final int depth,
                final ISeq<? extends Op<A>> operations,
                final ISeq<? extends Op<A>> terminals
        ) {
                return of(
                        depth,
                        (Predicate<? super ProgramChromosome<A>> & Serializable)
                                ProgramChromosome::isSuperValid,
                        operations,
                        terminals
                );
        }

        /**
         * Create a new program chromosome from the given (flattened) program tree.
         * This method doesn't make any assumption about the validity of the given
         * operation tree. If the tree is not valid, it will repair it. This
         * behaviour allows the <em>safe</em> usage of all existing alterers.
         *
         * {@snippet lang="java":
         * final ProgramChromosome<Double> ch = ProgramChromosome.of(
         *     genes,
         *     // If the program has more that 200 nodes, it is marked as "invalid".
         *     ch -> ch.length() <= 200,
         *     operations,
         *     terminals
         * );
         * }
         *
         * @param genes the program genes
         * @param validator the chromosome validator to use
         * @param operations the allowed non-terminal operations
         * @param terminals the allowed terminal operations
         * @param <A> the operation type
         * @return a new program chromosome from the given (flattened) program tree
         * @throws NullPointerException if one of the parameters is {@code null}
         */
        public static <A> ProgramChromosome<A> of(
                final ISeq<ProgramGene<A>> genes,
                final Predicate<? super ProgramChromosome<A>> validator,
                final ISeq<? extends Op<A>> operations,
                final ISeq<? extends Op<A>> terminals
        ) {
                final TreeNode<Op<A>> program = Program.toTree(genes, terminals);
                return of(program, validator, operations, terminals);
        }

        private static <A> ProgramChromosome<A> create(
                final ISeq<ProgramGene<A>> genes,
                final Predicate<? super ProgramChromosome<A>> validator,
                final ISeq<? extends Op<A>> operations,
                final ISeq<? extends Op<A>> terminals
        ) {
                final TreeNode<Op<A>> program = Program.toTree(genes, terminals);
                return create(program, validator, operations, terminals);
        }

        public static <A> ProgramChromosome<A> of(
                final ISeq<ProgramGene<A>> genes,
                final ISeq<? extends Op<A>> operations,
                final ISeq<? extends Op<A>> terminals
        ) {
                return of(genes, ProgramChromosome::isSuperValid, operations, terminals);
        }


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

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

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

        void write(final ObjectOutput out) throws IOException {
                writeInt(length(), out);
                out.writeObject(_operations);
                out.writeObject(_terminals);

                for (ProgramGene<A> gene : _genes) {
                        out.writeObject(gene.allele());
                        writeInt(gene.childOffset(), out);
                }
        }

        @SuppressWarnings({"unchecked", "rawtypes"})
        static ProgramChromosome read(final ObjectInput in)
                throws IOException, ClassNotFoundException
        {
                final var length = readInt(in);
                final var operations = (ISeq)in.readObject();
                final var terminals = (ISeq)in.readObject();

                final MSeq genes = MSeq.ofLength(length);
                for (int i = 0; i < genes.length(); ++i) {
                        final Op op = (Op)in.readObject();
                        final int childOffset = readInt(in);
                        genes.set(i, new ProgramGene(op, childOffset, operations, terminals));
                }

                return ProgramChromosome.of(genes.toISeq(), operations, terminals);
        }

}