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 io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.internal.disposables.SequentialDisposable;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  /**
   * Delays the subscription to the main source until the other
   * observable fires an event or completes.
   * @param <T> the main type
   * @param <U> the other value type, ignored
   */
  public final class ObservableDelaySubscriptionOther<T, U> extends Observable<T> {
      final ObservableSource<? extends T> main;
      final ObservableSource<U> other;
  
      public ObservableDelaySubscriptionOther(ObservableSource<? extends T> main, ObservableSource<U> other) {
          this.main = main;
          this.other = other;
      }
  
      @Override
      public void subscribeActual(final Observer<? super T> child) {
          final SequentialDisposable serial = new SequentialDisposable();
          child.onSubscribe(serial);
  
          Observer<U> otherObserver = new DelayObserver(serial, child);
  
          other.subscribe(otherObserver);
      }
  
      final class DelayObserver implements Observer<U> {
          final SequentialDisposable serial;
          final Observer<? super T> child;
          boolean done;
  
          DelayObserver(SequentialDisposable serial, Observer<? super T> child) {
              this.serial = serial;
              this.child = child;
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              serial.update(d);
          }
  
          @Override
          public void onNext(U t) {
              onComplete();
          }
  
          @Override
          public void onError(Throwable e) {
              if (done) {
                  RxJavaPlugins.onError(e);
                  return;
              }
              done = true;
              child.onError(e);
          }
  
          @Override
          public void onComplete() {
              if (done) {
                  return;
              }
              done = true;
  
              main.subscribe(new OnComplete());
          }
  
          final class OnComplete implements Observer<T> {
              @Override
              public void onSubscribe(Disposable d) {
                  serial.update(d);
              }
  
              @Override
              public void onNext(T value) {
                  child.onNext(value);
              }
  
              @Override
              public void onError(Throwable e) {
                  child.onError(e);
              }
  
              @Override
              public void onComplete() {
                  child.onComplete();
              }
          }
      }
  }
  