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 java.util.Objects;
  import java.util.concurrent.atomic.AtomicReference;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.functions.Function;
  import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
  
  /**
   * Maps the success value of the source SingleSource into a Completable.
   * @param <T> the value type of the source SingleSource
   */
  public final class SingleFlatMapCompletable<T> extends Completable {
  
      final SingleSource<T> source;
  
      final Function<? super T, ? extends CompletableSource> mapper;
  
      public SingleFlatMapCompletable(SingleSource<T> source, Function<? super T, ? extends CompletableSource> mapper) {
          this.source = source;
          this.mapper = mapper;
      }
  
      @Override
      protected void subscribeActual(CompletableObserver observer) {
          FlatMapCompletableObserver<T> parent = new FlatMapCompletableObserver<>(observer, mapper);
          observer.onSubscribe(parent);
          source.subscribe(parent);
      }
  
      static final class FlatMapCompletableObserver<T>
      extends AtomicReference<Disposable>
      implements SingleObserver<T>, CompletableObserver, Disposable {
  
          private static final long serialVersionUID = -2177128922851101253L;
  
          final CompletableObserver downstream;
  
          final Function<? super T, ? extends CompletableSource> mapper;
  
          FlatMapCompletableObserver(CompletableObserver actual,
                  Function<? super T, ? extends CompletableSource> mapper) {
              this.downstream = actual;
              this.mapper = mapper;
          }
  
          @Override
          public void dispose() {
              DisposableHelper.dispose(this);
          }
  
          @Override
          public boolean isDisposed() {
              return DisposableHelper.isDisposed(get());
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              DisposableHelper.replace(this, d);
          }
  
          @Override
          public void onSuccess(T value) {
              CompletableSource cs;
  
              try {
                  cs = Objects.requireNonNull(mapper.apply(value), "The mapper returned a null CompletableSource");
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  onError(ex);
                  return;
              }
  
              if (!isDisposed()) {
                  cs.subscribe(this);
              }
          }
  
          @Override
          public void onError(Throwable e) {
              downstream.onError(e);
          }
  
          @Override
          public void onComplete() {
              downstream.onComplete();
          }
      }
  }
  