001/*
002 * Java Genetic Algorithm Library (jenetics-7.2.0).
003 * Copyright (c) 2007-2023 Franz Wilhelmstötter
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 *
017 * Author:
018 *    Franz Wilhelmstötter (franz.wilhelmstoetter@gmail.com)
019 */
020package io.jenetics.ext.internal.parser;
021
022import static java.lang.String.format;
023
024import io.jenetics.ext.internal.parser.Token.Type;
025
026/**
027 * Parser implementation for parsing explicit {@link Token} sequences.
028 *
029 * @param <V> the token value type
030 *
031 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
032 * @since 7.1
033 * @version 7.1
034 */
035public class TokenParser<V> extends Parser<Token<V>> {
036
037        /**
038         * Create a new parser object with the given {@code tokenizer} and lookahead
039         * count {@code k}.
040         *
041         * @param tokenizer the token source {@code this} parser uses
042         * @param k the lookahead count
043         */
044        public TokenParser(final Tokenizer<Token<V>> tokenizer, final int k) {
045                super(tokenizer, k);
046        }
047
048        /**
049         * Return the token type code for the given lookahead index.
050         *
051         * @param index lookahead index
052         * @return the token type code for the given lookahead index
053         */
054        public int LA(final int index) {
055                final var token = LT(index);
056                return token != null ? token.type().code() : Type.EOF.code();
057        }
058
059        /**
060         * Try to <em>match</em> and consume the next token of the given
061         * {@code type}. If the current token is not from the given type, a
062         * {@link ParsingException} is thrown.
063         *
064         * @param type the token type to match
065         * @return the matched token
066         * @throws NullPointerException if the given token {@code type} is
067         *        {@code null}
068         * @throws ParsingException if the current token doesn't match the desired
069         *        token {@code type}
070         */
071        public Token<V> match(final Type type) {
072                if (LA(1) == type.code()) {
073                        final var token = LT(1);
074                        consume();
075                        return token;
076                } else {
077                        throw new ParsingException(format(
078                                "Expecting %s but found %s.",
079                                type, LT(1)
080                        ));
081                }
082        }
083
084}