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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you 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 org.apache.baremaps.openstreetmap.stream;



import java.util.ArrayList;
import java.util.List;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.Consumer;

/**
 * A {@code BatchedSpliterator} wraps another spliterator and partition its elements according to a
 * given batch size when trySplit is invoked.
 *
 * @param 
 */
public class BatchedSpliterator implements Spliterator {

  private final Spliterator spliterator;
  private final int batchSize;

  /**
   * Creates a spliterator that partitions the underlying spliterator according to a given batch
   * size.
   *
   * @param spliterator the underlying spliterator.
   * @param batchSize the batch size.
   */
  public BatchedSpliterator(Spliterator spliterator, int batchSize) {
    this.spliterator = spliterator;
    this.batchSize = batchSize;
  }

  @Override
  public boolean tryAdvance(Consumer action) {
    return this.spliterator.tryAdvance(action);
  }

  /**
   * Returns a spliterator covering the elements of a batch.
   *
   * @return a spliterator covering the elements of a batch.
   */
  @Override
  public Spliterator trySplit() {
    List batch = new ArrayList<>();
    while (batch.size() < batchSize && tryAdvance(batch::add)) {
      // Do nothing
    }
    if (!batch.isEmpty()) {
      return Spliterators.spliterator(batch, characteristics());
    } else {
      return null;
    }
  }

  /**
   * Returns the size of the underlying spliterator.
   *
   * @return the size of the underlying spliterator.
   */
  @Override
  public long estimateSize() {
    return spliterator.estimateSize();
  }

  /**
   * Returns the characteristics of the underlying spliterator with its ability to be subsized.
   *
   * @return a representation of characteristics.
   */
  @Override
  public int characteristics() {
    return spliterator.characteristics() | SIZED | SUBSIZED;
  }
}