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 io.reactivex.rxjava3.annotations.NonNull;
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.functions.*;
  import io.reactivex.rxjava3.internal.disposables.*;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  /**
   * Invokes callbacks upon {@code onSubscribe} from upstream and
   * {@code dispose} from downstream.
   *
   * @param <T> the element type of the flow
   * @since 3.0.0
   */
  public final class SingleDoOnLifecycle<T> extends Single<T> {
  
      final Single<T> source;
  
      final Consumer<? super Disposable> onSubscribe;
  
      final Action onDispose;
  
      public SingleDoOnLifecycle(Single<T> upstream, Consumer<? super Disposable> onSubscribe,
              Action onDispose) {
          this.source = upstream;
          this.onSubscribe = onSubscribe;
          this.onDispose = onDispose;
      }
  
      @Override
      protected void subscribeActual(SingleObserver<? super T> observer) {
          source.subscribe(new SingleLifecycleObserver<>(observer, onSubscribe, onDispose));
      }
  
      static final class SingleLifecycleObserver<T> implements SingleObserver<T>, Disposable {
  
          final SingleObserver<? super T> downstream;
  
          final Consumer<? super Disposable> onSubscribe;
  
          final Action onDispose;
  
          Disposable upstream;
  
          SingleLifecycleObserver(SingleObserver<? super T> downstream, Consumer<? super Disposable> onSubscribe, Action onDispose) {
              this.downstream = downstream;
              this.onSubscribe = onSubscribe;
              this.onDispose = onDispose;
          }
  
          @Override
          public void onSubscribe(@NonNull Disposable d) {
              // this way, multiple calls to onSubscribe can show up in tests that use doOnSubscribe to validate behavior
              try {
                  onSubscribe.accept(d);
              } catch (Throwable e) {
                  Exceptions.throwIfFatal(e);
                  d.dispose();
                  this.upstream = DisposableHelper.DISPOSED;
                  EmptyDisposable.error(e, downstream);
                  return;
              }
              if (DisposableHelper.validate(this.upstream, d)) {
                  this.upstream = d;
                  downstream.onSubscribe(this);
              }
          }
  
          @Override
          public void onSuccess(@NonNull T t) {
              if (upstream != DisposableHelper.DISPOSED) {
                  upstream = DisposableHelper.DISPOSED;
                  downstream.onSuccess(t);
              }
          }
  
          @Override
          public void onError(@NonNull Throwable e) {
              if (upstream != DisposableHelper.DISPOSED) {
                  upstream = DisposableHelper.DISPOSED;
                  downstream.onError(e);
              } else {
                  RxJavaPlugins.onError(e);
              }
          }
  
          @Override
          public void dispose() {
              try {
                  onDispose.run();
              } catch (Throwable e) {
                  Exceptions.throwIfFatal(e);
                  RxJavaPlugins.onError(e);
              }
              upstream.dispose();
              upstream = DisposableHelper.DISPOSED;
          }
  
          @Override
          public boolean isDisposed() {
              return upstream.isDisposed();
          }
      }
  }
  