code: /*
   * Copyright (c) 2016-present, RxJava 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 io.reactivex.rxjava3.internal.jdk8;
  
  import java.util.NoSuchElementException;
  import java.util.concurrent.CompletableFuture;
  import java.util.concurrent.atomic.AtomicReference;
  
  import io.reactivex.rxjava3.annotations.NonNull;
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  /**
   * Class that extends CompletableFuture and converts multiple types of reactive consumers
   * and their signals into completion signals.
   * @param <T> the element type
   * @since 3.0.0
   */
  public final class CompletionStageConsumer<T> extends CompletableFuture<T>
  implements MaybeObserver<T>, SingleObserver<T>, CompletableObserver {
  
      final AtomicReference<Disposable> upstream;
  
      final boolean hasDefault;
  
      final T defaultItem;
  
      public CompletionStageConsumer(boolean hasDefault, T defaultItem) {
          this.hasDefault = hasDefault;
          this.defaultItem = defaultItem;
          this.upstream = new AtomicReference<>();
      }
  
      @Override
      public void onSubscribe(@NonNull Disposable d) {
          DisposableHelper.setOnce(upstream, d);
      }
  
      @Override
      public void onSuccess(@NonNull T t) {
          clear();
          complete(t);
      }
  
      @Override
      public void onError(Throwable t) {
          clear();
          if (!completeExceptionally(t)) {
              RxJavaPlugins.onError(t);
          }
      }
  
      @Override
      public void onComplete() {
          if (hasDefault) {
              complete(defaultItem);
          } else {
              completeExceptionally(new NoSuchElementException("The source was empty"));
          }
      }
  
      void cancelUpstream() {
          DisposableHelper.dispose(upstream);
      }
  
      void clear() {
          upstream.lazySet(DisposableHelper.DISPOSED);
      }
  
      @Override
      public boolean cancel(boolean mayInterruptIfRunning) {
          cancelUpstream();
          return super.cancel(mayInterruptIfRunning);
      }
  
      @Override
      public boolean complete(T value) {
          cancelUpstream();
          return super.complete(value);
      }
  
      @Override
      public boolean completeExceptionally(Throwable ex) {
          cancelUpstream();
          return super.completeExceptionally(ex);
      }
  }
  