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.observers;
  
  import java.util.concurrent.atomic.AtomicReference;
  
  import io.reactivex.rxjava3.core.Observer;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
  import io.reactivex.rxjava3.internal.util.QueueDrainHelper;
  import io.reactivex.rxjava3.operators.QueueDisposable;
  import io.reactivex.rxjava3.operators.QueueSubscription;
  import io.reactivex.rxjava3.operators.SimpleQueue;
  
  /**
   * Subscriber that can fuse with the upstream and calls a support interface
   * whenever an event is available.
   *
   * @param <T> the value type
   */
  public final class InnerQueuedObserver<T>
  extends AtomicReference<Disposable>
  implements Observer<T>, Disposable {
  
      private static final long serialVersionUID = -5417183359794346637L;
  
      final InnerQueuedObserverSupport<T> parent;
  
      final int prefetch;
  
      SimpleQueue<T> queue;
  
      volatile boolean done;
  
      int fusionMode;
  
      public InnerQueuedObserver(InnerQueuedObserverSupport<T> parent, int prefetch) {
          this.parent = parent;
          this.prefetch = prefetch;
      }
  
      @Override
      public void onSubscribe(Disposable d) {
          if (DisposableHelper.setOnce(this, d)) {
              if (d instanceof QueueDisposable) {
                  @SuppressWarnings("unchecked")
                  QueueDisposable<T> qd = (QueueDisposable<T>) d;
  
                  int m = qd.requestFusion(QueueDisposable.ANY);
                  if (m == QueueSubscription.SYNC) {
                      fusionMode = m;
                      queue = qd;
                      done = true;
                      parent.innerComplete(this);
                      return;
                  }
                  if (m == QueueDisposable.ASYNC) {
                      fusionMode = m;
                      queue = qd;
                      return;
                  }
              }
  
              queue = QueueDrainHelper.createQueue(-prefetch);
          }
      }
  
      @Override
      public void onNext(T t) {
          if (fusionMode == QueueDisposable.NONE) {
              parent.innerNext(this, t);
          } else {
              parent.drain();
          }
      }
  
      @Override
      public void onError(Throwable t) {
          parent.innerError(this, t);
      }
  
      @Override
      public void onComplete() {
          parent.innerComplete(this);
      }
  
      @Override
      public void dispose() {
          DisposableHelper.dispose(this);
      }
  
      @Override
      public boolean isDisposed() {
          return DisposableHelper.isDisposed(get());
      }
  
      public boolean isDone() {
          return done;
      }
  
      public void setDone() {
          this.done = true;
      }
  
      public SimpleQueue<T> queue() {
          return queue;
      }
  }
  