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.flowable;
  
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.internal.subscriptions.SubscriptionArbiter;
  
  public final class FlowableSwitchIfEmpty<T> extends AbstractFlowableWithUpstream<T, T> {
      final Publisher<? extends T> other;
      public FlowableSwitchIfEmpty(Flowable<T> source, Publisher<? extends T> other) {
          super(source);
          this.other = other;
      }
  
      @Override
      protected void subscribeActual(Subscriber<? super T> s) {
          SwitchIfEmptySubscriber<T> parent = new SwitchIfEmptySubscriber<>(s, other);
          s.onSubscribe(parent.arbiter);
          source.subscribe(parent);
      }
  
      static final class SwitchIfEmptySubscriber<T> implements FlowableSubscriber<T> {
          final Subscriber<? super T> downstream;
          final Publisher<? extends T> other;
          final SubscriptionArbiter arbiter;
  
          boolean empty;
  
          SwitchIfEmptySubscriber(Subscriber<? super T> actual, Publisher<? extends T> other) {
              this.downstream = actual;
              this.other = other;
              this.empty = true;
              this.arbiter = new SubscriptionArbiter(false);
          }
  
          @Override
          public void onSubscribe(Subscription s) {
              arbiter.setSubscription(s);
          }
  
          @Override
          public void onNext(T t) {
              if (empty) {
                  empty = false;
              }
              downstream.onNext(t);
          }
  
          @Override
          public void onError(Throwable t) {
              downstream.onError(t);
          }
  
          @Override
          public void onComplete() {
              if (empty) {
                  empty = false;
                  other.subscribe(this);
              } else {
                  downstream.onComplete();
              }
          }
      }
  }
  