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.maybe;
  
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.exceptions.CompositeException;
  import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
  import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
  
  /**
   * Delay the emission of the main signal until the other signals an item or completes.
   * 
   * @param <T> the main value type
   * @param <U> the other value type
   */
  public final class MaybeDelayOtherPublisher<T, U> extends AbstractMaybeWithUpstream<T, T> {
  
      final Publisher<U> other;
  
      public MaybeDelayOtherPublisher(MaybeSource<T> source, Publisher<U> other) {
          super(source);
          this.other = other;
      }
  
      @Override
      protected void subscribeActual(MaybeObserver<? super T> observer) {
          source.subscribe(new DelayMaybeObserver<>(observer, other));
      }
  
      static final class DelayMaybeObserver<T, U>
      implements MaybeObserver<T>, Disposable {
          final OtherSubscriber<T> other;
  
          final Publisher<U> otherSource;
  
          Disposable upstream;
  
          DelayMaybeObserver(MaybeObserver<? super T> actual, Publisher<U> otherSource) {
              this.other = new OtherSubscriber<>(actual);
              this.otherSource = otherSource;
          }
  
          @Override
          public void dispose() {
              upstream.dispose();
              upstream = DisposableHelper.DISPOSED;
              SubscriptionHelper.cancel(other);
          }
  
          @Override
          public boolean isDisposed() {
              return other.get() == SubscriptionHelper.CANCELLED;
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              if (DisposableHelper.validate(this.upstream, d)) {
                  this.upstream = d;
  
                  other.downstream.onSubscribe(this);
              }
          }
  
          @Override
          public void onSuccess(T value) {
              upstream = DisposableHelper.DISPOSED;
              other.value = value;
              subscribeNext();
          }
  
          @Override
          public void onError(Throwable e) {
              upstream = DisposableHelper.DISPOSED;
              other.error = e;
              subscribeNext();
          }
  
          @Override
          public void onComplete() {
              upstream = DisposableHelper.DISPOSED;
              subscribeNext();
          }
  
          void subscribeNext() {
              otherSource.subscribe(other);
          }
      }
  
      static final class OtherSubscriber<T> extends
      AtomicReference<Subscription>
      implements FlowableSubscriber<Object> {
  
          private static final long serialVersionUID = -1215060610805418006L;
  
          final MaybeObserver<? super T> downstream;
  
          T value;
  
          Throwable error;
  
          OtherSubscriber(MaybeObserver<? super T> downstream) {
              this.downstream = downstream;
          }
  
          @Override
          public void onSubscribe(Subscription s) {
              SubscriptionHelper.setOnce(this, s, Long.MAX_VALUE);
          }
  
          @Override
          public void onNext(Object t) {
              Subscription s = get();
              if (s != SubscriptionHelper.CANCELLED) {
                  lazySet(SubscriptionHelper.CANCELLED);
                  s.cancel();
                  onComplete();
              }
          }
  
          @Override
          public void onError(Throwable t) {
              Throwable e = error;
              if (e == null) {
                  downstream.onError(t);
              } else {
                  downstream.onError(new CompositeException(e, t));
              }
          }
  
          @Override
          public void onComplete() {
              Throwable e = error;
              if (e != null) {
                  downstream.onError(e);
              } else {
                  T v = value;
                  if (v != null) {
                      downstream.onSuccess(v);
                  } else {
                      downstream.onComplete();
                  }
              }
          }
      }
  }
  