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.single;
  
  import static io.reactivex.rxjava3.internal.util.ExceptionHelper.timeoutMessage;
  
  import java.util.concurrent.*;
  import java.util.concurrent.atomic.AtomicReference;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  public final class SingleTimeout<T> extends Single<T> {
  
      final SingleSource<T> source;
  
      final long timeout;
  
      final TimeUnit unit;
  
      final Scheduler scheduler;
  
      final SingleSource<? extends T> other;
  
      public SingleTimeout(SingleSource<T> source, long timeout, TimeUnit unit, Scheduler scheduler,
                           SingleSource<? extends T> other) {
          this.source = source;
          this.timeout = timeout;
          this.unit = unit;
          this.scheduler = scheduler;
          this.other = other;
      }
  
      @Override
      protected void subscribeActual(final SingleObserver<? super T> observer) {
  
          TimeoutMainObserver<T> parent = new TimeoutMainObserver<>(observer, other, timeout, unit);
          observer.onSubscribe(parent);
  
          DisposableHelper.replace(parent.task, scheduler.scheduleDirect(parent, timeout, unit));
  
          source.subscribe(parent);
      }
  
      static final class TimeoutMainObserver<T> extends AtomicReference<Disposable>
      implements SingleObserver<T>, Runnable, Disposable {
  
          private static final long serialVersionUID = 37497744973048446L;
  
          final SingleObserver<? super T> downstream;
  
          final AtomicReference<Disposable> task;
  
          final TimeoutFallbackObserver<T> fallback;
  
          SingleSource<? extends T> other;
  
          final long timeout;
  
          final TimeUnit unit;
  
          static final class TimeoutFallbackObserver<T> extends AtomicReference<Disposable>
          implements SingleObserver<T> {
  
              private static final long serialVersionUID = 2071387740092105509L;
              final SingleObserver<? super T> downstream;
  
              TimeoutFallbackObserver(SingleObserver<? super T> downstream) {
                  this.downstream = downstream;
              }
  
              @Override
              public void onSubscribe(Disposable d) {
                  DisposableHelper.setOnce(this, d);
              }
  
              @Override
              public void onSuccess(T t) {
                  downstream.onSuccess(t);
              }
  
              @Override
              public void onError(Throwable e) {
                  downstream.onError(e);
              }
          }
  
          TimeoutMainObserver(SingleObserver<? super T> actual, SingleSource<? extends T> other, long timeout, TimeUnit unit) {
              this.downstream = actual;
              this.other = other;
              this.timeout = timeout;
              this.unit = unit;
              this.task = new AtomicReference<>();
              if (other != null) {
                  this.fallback = new TimeoutFallbackObserver<>(actual);
              } else {
                  this.fallback = null;
              }
          }
  
          @Override
          public void run() {
              if (DisposableHelper.dispose(this)) {
                  SingleSource<? extends T> other = this.other;
                  if (other == null) {
                      downstream.onError(new TimeoutException(timeoutMessage(timeout, unit)));
                  } else {
                      this.other = null;
                      other.subscribe(fallback);
                  }
              }
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              DisposableHelper.setOnce(this, d);
          }
  
          @Override
          public void onSuccess(T t) {
              Disposable d = get();
              if (d != DisposableHelper.DISPOSED && compareAndSet(d, DisposableHelper.DISPOSED)) {
                  DisposableHelper.dispose(task);
                  downstream.onSuccess(t);
              }
          }
  
          @Override
          public void onError(Throwable e) {
              Disposable d = get();
              if (d != DisposableHelper.DISPOSED && compareAndSet(d, DisposableHelper.DISPOSED)) {
                  DisposableHelper.dispose(task);
                  downstream.onError(e);
              } else {
                  RxJavaPlugins.onError(e);
              }
          }
  
          @Override
          public void dispose() {
              DisposableHelper.dispose(this);
              DisposableHelper.dispose(task);
              if (fallback != null) {
                  DisposableHelper.dispose(fallback);
              }
          }
  
          @Override
          public boolean isDisposed() {
              return DisposableHelper.isDisposed(get());
          }
      }
  }
  