/*
 * Java Genetic Algorithm Library (jenetics-7.1.0).
 * Copyright (c) 2007-2022 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.op;

import static java.util.Objects.requireNonNull;

import java.util.Objects;
import java.util.Optional;
import java.util.function.Function;
import java.util.stream.Stream;

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

/**
 * This class contains basic and secondary boolean operations.
 *
 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
 * @version 5.0
 * @since 5.0
 */
public enum BoolOp implements Op<Boolean> {

        /**
         * Conjunction. <em>This operation has arity 2.</em>
         */
        AND("and", 2, v -> v[0] && v[1]),

        /**
         * Disjunction. <em>This operation has arity 2.</em>
         */
        OR("or", 2, v -> v[0] || v[1]),

        /**
         * Negation. <em>This operation has arity 1.</em>
         */
        NOT("not", 1, v -> !v[0]),

        /**
         * Implication. <em>This operation has arity 2.</em>
         */
        IMP("imp", 2, v -> !v[0] || v[1]),

        /**
         * Exclusive or. <em>This operation has arity 2.</em>
         */
        XOR("xor", 2, v -> (v[0] || v[1]) && !(v[0] && v[1])),

        /**
         * Equivalence. <em>This operation has arity 2.</em>
         */
        EQU("equ", 2, v -> (v[0] && v[1]) || (!v[0] && !v[1]));

        /**
         * Represents the constant {@code true}.
         */
        public static final Const<Boolean> TRUE = Const.of("true", true);

        /**
         * Represents the constant {@code true}.
         */
        public static final Const<Boolean> FALSE = Const.of("false", false);


        private final String _name;
        private final int _arity;
        private final Function<Boolean[], Boolean> _function;

        BoolOp(
                final String name,
                final int arity,
                final Function<Boolean[], Boolean> function
        ) {
                assert name != null;
                assert arity >= 0;
                assert function != null;

                _name = name;
                _function = function;
                _arity = arity;
        }

        @Override
        public int arity() {
                return _arity;
        }

        @Override
        public Boolean apply(final Boolean[] args) {
                return _function.apply(args);
        }

        /**
         * Evaluates the operation with the given arguments.
         *
         * @see #apply(Boolean[])
         *
         * @param args the operation arguments
         * @return the evaluated operation
         */
        public boolean eval(final boolean... args) {
                final Boolean[] v = new Boolean[args.length];
                for (int i = 0; i < args.length; ++i) {
                        v[i] = args[i];
                }

                return apply(v);
        }

        @Override
        public String toString() {
                return _name;
        }


        /**
         * Converts the string representation of an operation to the operation
         * object. It is used for converting the string representation of a tree to
         * an operation tree. If you use it that way, you should not forget to
         * re-index the tree variables.
         *
         * <pre>{@code
         * final TreeNode<Op<Boolean>> tree = TreeNode.parse(
         *     "and(or(x,y),not(y))",
         *     BoolOp::toBoolOp
         * );
         *
         * assert Program.eval(tree, false, false) == false;
         * Var.reindex(tree);
         * assert Program.eval(tree, false, false) == true;
         * }</pre>
         *
         * @since 5.0
         *
         * @see Var#reindex(TreeNode)
         * @see Program#eval(Tree, Object[])
         *
         * @param string the string representation of an operation which should be
         *        converted
         * @return the operation, converted from the given string
         * @throws IllegalArgumentException if the given {@code value} doesn't
         *         represent a mathematical expression
         * @throws NullPointerException if the given string {@code value} is
         *         {@code null}
         */
        public static Op<Boolean> toBoolOp(final String string) {
                requireNonNull(string);

                final Op<Boolean> result;
                final Optional<Const<Boolean>> cop = toConst(string);
                if (cop.isPresent()) {
                        result = cop.orElseThrow(AssertionError::new);
                } else {
                        final Optional<Op<Boolean>> mop = toOp(string);
                        result = mop.isPresent()
                                ? mop.orElseThrow(AssertionError::new)
                                : Var.parse(string);
                }

                return result;
        }

        static Optional<Const<Boolean>> toConst(final String string) {
                return tryParseBoolean(string)
                        .map(Const::of);
        }

        private static Optional<Boolean> tryParseBoolean(final String value) {
                switch (value) {
                        case "true":
                        case "1": return Optional.of(true);
                        case "false":
                        case "0": return Optional.of(false);
                        default: return Optional.empty();
                }
        }

        private static Optional<Op<Boolean>> toOp(final String string) {
                return Stream.of(values())
                        .filter(op -> Objects.equals(op._name, string))
                        .map(op -> (Op<Boolean>)op)
                        .findFirst();
        }

}