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.operators.observable;
  
  import java.util.concurrent.atomic.AtomicReference;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
  
  /**
   * Subscribe to a main Observable first, then when it completes normally, subscribe to a Maybe,
   * signal its success value followed by a completion or signal its error or completion signal as is.
   * <p>History: 2.1.10 - experimental
   * @param <T> the element type of the main source and output type
   * @since 2.2
   */
  public final class ObservableConcatWithMaybe<T> extends AbstractObservableWithUpstream<T, T> {
  
      final MaybeSource<? extends T> other;
  
      public ObservableConcatWithMaybe(Observable<T> source, MaybeSource<? extends T> other) {
          super(source);
          this.other = other;
      }
  
      @Override
      protected void subscribeActual(Observer<? super T> observer) {
          source.subscribe(new ConcatWithObserver<>(observer, other));
      }
  
      static final class ConcatWithObserver<T>
      extends AtomicReference<Disposable>
      implements Observer<T>, MaybeObserver<T>, Disposable {
  
          private static final long serialVersionUID = -1953724749712440952L;
  
          final Observer<? super T> downstream;
  
          MaybeSource<? extends T> other;
  
          boolean inMaybe;
  
          ConcatWithObserver(Observer<? super T> actual, MaybeSource<? extends T> other) {
              this.downstream = actual;
              this.other = other;
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              if (DisposableHelper.setOnce(this, d) && !inMaybe) {
                  downstream.onSubscribe(this);
              }
          }
  
          @Override
          public void onNext(T t) {
              downstream.onNext(t);
          }
  
          @Override
          public void onSuccess(T t) {
              downstream.onNext(t);
              downstream.onComplete();
          }
  
          @Override
          public void onError(Throwable e) {
              downstream.onError(e);
          }
  
          @Override
          public void onComplete() {
              if (inMaybe) {
                  downstream.onComplete();
              } else {
                  inMaybe = true;
                  DisposableHelper.replace(this, null);
                  MaybeSource<? extends T> ms = other;
                  other = null;
                  ms.subscribe(this);
              }
          }
  
          @Override
          public void dispose() {
              DisposableHelper.dispose(this);
          }
  
          @Override
          public boolean isDisposed() {
              return DisposableHelper.isDisposed(get());
          }
      }
  }
  