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.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.functions.Consumer;
  import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  /**
   * Calls a consumer after pushing the current item to the downstream.
   * <p>History: 2.0.1 - experimental
   * @param <T> the value type
   * @since 2.1
   */
  public final class SingleDoAfterSuccess<T> extends Single<T> {
  
      final SingleSource<T> source;
  
      final Consumer<? super T> onAfterSuccess;
  
      public SingleDoAfterSuccess(SingleSource<T> source, Consumer<? super T> onAfterSuccess) {
          this.source = source;
          this.onAfterSuccess = onAfterSuccess;
      }
  
      @Override
      protected void subscribeActual(SingleObserver<? super T> observer) {
          source.subscribe(new DoAfterObserver<>(observer, onAfterSuccess));
      }
  
      static final class DoAfterObserver<T> implements SingleObserver<T>, Disposable {
  
          final SingleObserver<? super T> downstream;
  
          final Consumer<? super T> onAfterSuccess;
  
          Disposable upstream;
  
          DoAfterObserver(SingleObserver<? super T> actual, Consumer<? super T> onAfterSuccess) {
              this.downstream = actual;
              this.onAfterSuccess = onAfterSuccess;
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              if (DisposableHelper.validate(this.upstream, d)) {
                  this.upstream = d;
  
                  downstream.onSubscribe(this);
              }
          }
  
          @Override
          public void onSuccess(T t) {
              downstream.onSuccess(t);
  
              try {
                  onAfterSuccess.accept(t);
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
               // remember, onSuccess is a terminal event and we can't call onError
                  RxJavaPlugins.onError(ex);
              }
          }
  
          @Override
          public void onError(Throwable e) {
              downstream.onError(e);
          }
  
          @Override
          public void dispose() {
              upstream.dispose();
          }
  
          @Override
          public boolean isDisposed() {
              return upstream.isDisposed();
          }
      }
  }
  