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.ArrayDeque;
  import java.util.Spliterator;
  import java.util.function.*;
  
  import static one.util.streamex.Internals.CancelException;
  import static one.util.streamex.Internals.CloneableSpliterator;
  
  /**
   * @author Tagir Valeev
   */
  /* package */final class OrderedCancellableSpliterator<T, A> extends CloneableSpliterator<A, OrderedCancellableSpliterator<T, A>> {
      private Spliterator<T> source;
      private final Object lock = new Object();
      private final BiConsumer<A, ? super T> accumulator;
      private final Predicate<A> cancelPredicate;
      private final BinaryOperator<A> combiner;
      private final Supplier<A> supplier;
      private volatile boolean localCancelled;
      private volatile OrderedCancellableSpliterator<T, A> prefix;
      private volatile OrderedCancellableSpliterator<T, A> suffix;
      private A payload;
  
      OrderedCancellableSpliterator(Spliterator<T> source, Supplier<A> supplier, BiConsumer<A, ? super T> accumulator,
              BinaryOperator<A> combiner, Predicate<A> cancelPredicate) {
          this.source = source;
          this.supplier = supplier;
          this.accumulator = accumulator;
          this.combiner = combiner;
          this.cancelPredicate = cancelPredicate;
      }
  
      @Override
      public boolean tryAdvance(Consumer<? super A> action) {
          Spliterator<T> source = this.source;
          if (source == null || localCancelled) {
              this.source = null;
              return false;
          }
          A acc = supplier.get();
          try {
              source.forEachRemaining(t -> {
                  accumulator.accept(acc, t);
                  if (cancelPredicate.test(acc)) {
                      cancelSuffix();
                      throw new CancelException();
                  }
                  if (localCancelled) {
                      throw new CancelException();
                  }
              });
          } catch (CancelException ex) {
              if (localCancelled) {
                  return false;
              }
          }
          this.source = null;
          A result = acc;
          while (true) {
              if (prefix == null && suffix == null) {
                  action.accept(result);
                  return true;
              }
              ArrayDeque<A> res = new ArrayDeque<>();
              res.offer(result);
              synchronized (lock) {
                  if (localCancelled)
                      return false;
                  OrderedCancellableSpliterator<T, A> s = prefix;
                  while (s != null) {
                      if (s.payload == null)
                          break;
                      res.offerFirst(s.payload);
                      s = s.prefix;
                  }
                  prefix = s;
                  if (s != null) {
                      s.suffix = this;
                  }
                  s = suffix;
                  while (s != null) {
                      if (s.payload == null)
                          break;
                      res.offerLast(s.payload);
                      s = s.suffix;
                  }
                  suffix = s;
                  if (s != null) {
                      s.prefix = this;
                  }
                  if (res.size() == 1) {
                      if (prefix == null && suffix == null) {
                          action.accept(result);
                          return true;
                      }
                      this.payload = result;
                      break;
                  }
              }
              result = res.pollFirst();
              while (!res.isEmpty()) {
                  result = combiner.apply(result, res.pollFirst());
                  if (cancelPredicate.test(result)) {
                      cancelSuffix();
                  }
              }
          }
          return false;
      }
  
      private void cancelSuffix() {
          if (this.suffix == null)
              return;
          synchronized (lock) {
              OrderedCancellableSpliterator<T, A> suffix = this.suffix;
              while (suffix != null && !suffix.localCancelled) {
                  suffix.prefix = null;
                  suffix.localCancelled = true;
                  suffix = suffix.suffix;
              }
              this.suffix = null;
          }
      }
  
      @Override
      public void forEachRemaining(Consumer<? super A> action) {
          tryAdvance(action);
      }
  
      @Override
      public Spliterator<A> trySplit() {
          if (source == null || localCancelled) {
              source = null;
              return null;
          }
          Spliterator<T> prefix = source.trySplit();
          if (prefix == null) {
              return null;
          }
          synchronized (lock) {
              OrderedCancellableSpliterator<T, A> result = doClone();
              result.source = prefix;
              this.prefix = result;
              result.suffix = this;
              OrderedCancellableSpliterator<T, A> prefixPrefix = result.prefix;
              if (prefixPrefix != null)
                  prefixPrefix.suffix = result;
              return result;
          }
      }
  
      @Override
      public long estimateSize() {
          return source == null ? 0 : source.estimateSize();
      }
  
      @Override
      public int characteristics() {
          return source == null ? SIZED : ORDERED;
      }
  }
  