/*
 * 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.ext.rewriting;

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.Objects;
import java.util.function.Function;
import java.util.stream.Collectors;

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

import io.jenetics.ext.util.TreeNode;

/**
 * This class represents a Tree Rewrite System, which consists of a set of
 * Tree Rewrite Rules.
 * <pre>{@code
 * final TRS<String> trs = TRS.parse(
 *     "add(0,$x) -> $x",
 *     "add(S($x),$y) -> S(add($x,$y))",
 *     "mul(0,$x) -> 0",
 *     "mul(S($x),$y) -> add(mul($x,$y),$y)"
 * );
 *
 * // Converting the input tree into its normal form.
 * final TreeNode<String> tree = TreeNode.parse("add(S(0),S(mul(S(0),S(S(0)))))");
 * trs.rewrite(tree);
 * assert tree.equals(TreeNode.parse("S(S(S(S(0))))"));
 * }</pre>
 *
 * @see TreeRewriteRule
 * @see <a href="https://en.wikipedia.org/wiki/Rewriting">TRS</a>
 *
 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
 * @version 5.0
 * @since 5.0
 */
public final class TRS<V> implements TreeRewriter<V>, Serializable {

        @Serial
        private static final long serialVersionUID = 1L;

        private final ISeq<TreeRewriteRule<V>> _rules;

        /**
         * Create a new TRS from the given rewrite rules.
         *
         * @param rules the rewrite rules the TRS consists of
         * @throws NullPointerException if the given {@code rules} are {@code null}
         * @throws IllegalArgumentException if the given {@code rules} sequence is
         *         empty
         */
        public TRS(final ISeq<TreeRewriteRule<V>> rules) {
                if (rules.isEmpty()) {
                        throw new IllegalArgumentException("Rewrite rules must not be empty.");
                }
                _rules = rules;
        }

        @Override
        public int rewrite(final TreeNode<V> tree, final int limit) {
                return TreeRewriter.rewrite(tree, limit, _rules);
        }

        /**
         * Maps {@code this} TRS from type {@code V} to type {@code B}.
         *
         * @param mapper the type mapper
         * @param <B> the target type
         * @return a new TRS for the mapped type
         * @throws NullPointerException if the {@code mapper} is {@code null}
         */
        public <B> TRS<B> map(final Function<? super V, ? extends B> mapper) {
                return new TRS<>(_rules.map(rule -> rule.map(mapper)));
        }

        @Override
        public int hashCode() {
                return _rules.hashCode();
        }

        @Override
        public boolean equals(final Object obj) {
                return obj == this ||
                        obj instanceof TRS<?> other &&
                        _rules.equals(other._rules);
        }

        @Override
        public String toString() {
                return _rules.stream()
                        .map(Objects::toString)
                        .collect(Collectors.joining("; "));
        }

        /**
         * Create a new TRS from the given rewrite rules and type mapper.
         *
         * @param mapper the tree value type mapper
         * @param rules the rewrite rules
         * @param <V> the tree value type the rewriter is working on
         * @return a new TRS
         * @throws NullPointerException if one of the arguments is {@code null}
         * @throws IllegalArgumentException if the given {@code rules} sequence is
         *         empty
         */
        public static <V> TRS<V> parse(
                final Function<? super String, ? extends V> mapper,
                final String... rules
        ) {
                return new TRS<>(
                        ISeq.of(rules)
                                .map(rule -> TreeRewriteRule.parse(rule, mapper))
                );
        }

        /**
         * Create a new TRS from the given rewrite rules.
         *
         * @param rules the rewrite rules
         * @return a new TRS
         * @throws NullPointerException if one of the arguments is {@code null}
         * @throws IllegalArgumentException if the given {@code rules} sequence is
         *         empty
         */
        public static TRS<String> parse(final String... rules) {
                return parse(Function.identity(), rules);
        }

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

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

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

        void write(final ObjectOutput out) throws IOException {
                writeInt(_rules.length(), out);
                for (int i = 0; i < _rules.length(); ++i) {
                        out.writeObject(_rules.get(i));
                }
        }

        @SuppressWarnings({"unchecked", "rawtypes"})
        static Object read(final ObjectInput in)
                throws IOException, ClassNotFoundException
        {
                final var length = readInt(in);
                final var rules = MSeq.ofLength(length);
                for (int i = 0; i < length; ++i) {
                        rules.set(i, in.readObject());
                }

                return new TRS(rules.toISeq());
        }

}