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 java.util.Comparator;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Spliterator;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.atomic.AtomicLong;
  import java.util.function.Consumer;
  
  import static one.util.streamex.Internals.Box;
  
  /* package */final class DistinctSpliterator<T> extends Box<T> implements Spliterator<T> {
      private final Spliterator<T> source;
      private AtomicLong nullCounter;
      private Map<T, Long> counts;
      private final long atLeast;
  
      DistinctSpliterator(Spliterator<T> source, long atLeast, AtomicLong nullCounter, Map<T, Long> counts) {
          this.source = source;
          this.atLeast = atLeast;
          this.nullCounter = nullCounter;
          this.counts = counts;
      }
  
      DistinctSpliterator(Spliterator<T> source, long atLeast) {
          this(source, atLeast, null, new HashMap<>());
      }
  
      @Override
      public boolean tryAdvance(Consumer<? super T> action) {
          if (nullCounter == null) {
              while (source.tryAdvance(this)) {
                  if (counts.merge(a, 1L, Long::sum) == atLeast) {
                      action.accept(a);
                      return true;
                  }
              }
          } else {
              while (source.tryAdvance(this)) {
                  long count = a == null ? nullCounter.incrementAndGet() : counts.merge(a, 1L, Long::sum);
                  if (count == atLeast) {
                      action.accept(a);
                      return true;
                  }
              }
          }
          return false;
      }
  
      @Override
      public void forEachRemaining(Consumer<? super T> action) {
          if (nullCounter == null) {
              source.forEachRemaining(e -> {
                  if (counts.merge(e, 1L, Long::sum) == atLeast) {
                      action.accept(e);
                  }
              });
          } else {
              source.forEachRemaining(e -> {
                  long count = e == null ? nullCounter.incrementAndGet() : counts.merge(e, 1L, Long::sum);
                  if (count == atLeast) {
                      action.accept(e);
                  }
              });
          }
      }
  
      @Override
      public Spliterator<T> trySplit() {
          Spliterator<T> split = source.trySplit();
          if (split == null)
              return null;
          if (counts.getClass() == HashMap.class) {
              if (!source.hasCharacteristics(NONNULL)) {
                  Long current = counts.remove(null);
                  nullCounter = new AtomicLong(current == null ? 0 : current);
              }
              counts = new ConcurrentHashMap<>(counts);
          }
          return new DistinctSpliterator<>(split, atLeast, nullCounter, counts);
      }
  
      @Override
      public long estimateSize() {
          return source.estimateSize();
      }
  
      @Override
      public int characteristics() {
          return DISTINCT | (source.characteristics() & (NONNULL | CONCURRENT | IMMUTABLE | ORDERED | SORTED));
      }
  
      @Override
      public Comparator<? super T> getComparator() {
          return source.getComparator();
      }
  }
  