001/*
002 * Copyright 2020  nils.hoffmann.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016package de.isas.lipidomics.palinom;
017
018import java.util.Optional;
019import java.util.function.Function;
020import org.antlr.v4.runtime.tree.RuleNode;
021
022/**
023 * Common functions for ANTLRv4's RuleNode handling.
024 *
025 * @author nils.hoffmann
026 */
027public class HandlerUtils {
028
029    /**
030     * Parse the provided context's text value as an Integer or use default
031     * value.
032     *
033     * @param <T> the type of the context.
034     * @param context the context.
035     * @param defaultValue the default value.
036     * @return the context's text value as an integer, or the default value.
037     */
038    public static <T extends RuleNode> Integer asInt(T context, Integer defaultValue) {
039        return maybeMapOr(context, (t) -> {
040            return Integer.parseInt(t.getText());
041        }, defaultValue);
042    }
043
044    /**
045     * Wrap t as an optional of nullable.
046     *
047     * @param <T> the type of t.
048     * @param t the argument.
049     * @return an optional.
050     */
051    public static <T> Optional<T> maybe(T t) {
052        return Optional.ofNullable(t);
053    }
054
055    /**
056     * Wrap t as an optional and return r if t is null or empty.
057     *
058     * @param <T> the type of t.
059     * @param <R> the type of the return value r.
060     * @param t the argument to wrap.
061     * @param mapper the mapping function to get from t to r, if t is not null.
062     * @param r the default return value.
063     * @return the mapped value for t of type R, or the default value r.
064     */
065    public static <T, R> R maybeMapOr(T t, Function<? super T, R> mapper, R r) {
066        return maybe(t).map(mapper).orElse(r);
067    }
068
069}