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.util;
021
022import java.util.ArrayList;
023import java.util.List;
024import java.util.Objects;
025import java.util.Spliterator;
026import java.util.function.Consumer;
027import java.util.function.Supplier;
028
029/**
030 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
031 * @version 4.1
032 * @since 4.1
033 */
034public class CyclicSpliterator<T> implements Spliterator<T> {
035
036        private final List<Supplier<Spliterator<T>>> _spliterators;
037
038        private ConcatSpliterator<T> _concat = null;
039
040        public CyclicSpliterator(final List<Supplier<Spliterator<T>>> spliterators) {
041                spliterators.forEach(Objects::requireNonNull);
042                _spliterators = new ArrayList<>(spliterators);
043        }
044
045        @Override
046        public boolean tryAdvance(final Consumer<? super T> action) {
047                boolean advance = true;
048                if (_spliterators.isEmpty()) {
049                        advance = false;
050                } else {
051                        if (!spliterator().tryAdvance(action)) {
052                                _concat = null;
053                        }
054                }
055
056                return advance;
057        }
058
059        @Override
060        public Spliterator<T> trySplit() {
061                return new CyclicSpliterator<>(_spliterators);
062        }
063
064        @Override
065        public long estimateSize() {
066                return Long.MAX_VALUE;
067        }
068
069        @Override
070        public int characteristics() {
071                return Spliterator.ORDERED;
072        }
073
074        private ConcatSpliterator<T> spliterator() {
075                if (_concat == null) {
076                        _concat = new ConcatSpliterator<>(
077                                _spliterators.stream()
078                                        .map(Supplier::get)
079                                        .toList()
080                        );
081                }
082
083                return _concat;
084        }
085
086}