content: /*
   * Copyright 2015, 2024 StreamEx contributors
   *
   * 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.
   */
  package one.util.streamex;
  
  import one.util.streamex.Internals.TailSpliterator;
  
  import java.util.Spliterator;
  import java.util.function.Consumer;
  
  /**
   * @author Tagir Valeev
   *
   * @param <T> type of the elements
   */
  /* package */class PrependSpliterator<T> implements TailSpliterator<T> {
      private Spliterator<T> source;
      private T element;
      private int mode;
  
      public PrependSpliterator(Spliterator<T> source, T element) {
          this.source = source;
          this.element = element;
          this.mode = source.estimateSize() < Long.MAX_VALUE - 1 ? 1 : 2;
      }
  
      @Override
      public boolean tryAdvance(Consumer<? super T> action) {
          if (mode == 0)
              return source.tryAdvance(action);
          action.accept(element);
          element = null;
          mode = 0;
          return true;
      }
  
      @Override
      public Spliterator<T> tryAdvanceOrTail(Consumer<? super T> action) {
          if (mode == 0) {
              Spliterator<T> s = source;
              source = null;
              return s;
          }
          action.accept(element);
          element = null;
          mode = 0;
          return this;
      }
  
      @Override
      public void forEachRemaining(Consumer<? super T> action) {
          if (mode != 0)
              action.accept(element);
          element = null;
          mode = 0;
          source.forEachRemaining(action);
      }
  
      @Override
      public Spliterator<T> forEachOrTail(Consumer<? super T> action) {
          if (mode != 0) {
              action.accept(element);
          }
          Spliterator<T> s = source;
          element = null;
          mode = 0;
          source = null;
          return s;
      }
  
      @Override
      public Spliterator<T> trySplit() {
          if (mode == 0)
              return source.trySplit();
          mode = 0;
          return new ConstSpliterator.OfRef<>(element, 1, true);
      }
  
      @Override
      public long estimateSize() {
          long size = source.estimateSize();
          return mode == 0 || size == Long.MAX_VALUE ? size : size + 1;
      }
  
      @Override
      public int characteristics() {
          switch (mode) {
          case 1:
              return source.characteristics() & (ORDERED | SIZED | SUBSIZED);
          case 2:
              return source.characteristics() & ORDERED;
          default:
              return source.characteristics();
          }
      }
  }
  