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.*;
  import io.reactivex.rxjava3.functions.Function;
  import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
  import io.reactivex.rxjava3.internal.observers.ResumeSingleObserver;
  
  public final class SingleResumeNext<T> extends Single<T> {
      final SingleSource<? extends T> source;
  
      final Function<? super Throwable, ? extends SingleSource<? extends T>> nextFunction;
  
      public SingleResumeNext(SingleSource<? extends T> source,
              Function<? super Throwable, ? extends SingleSource<? extends T>> nextFunction) {
          this.source = source;
          this.nextFunction = nextFunction;
      }
  
      @Override
      protected void subscribeActual(final SingleObserver<? super T> observer) {
          source.subscribe(new ResumeMainSingleObserver<>(observer, nextFunction));
      }
  
      static final class ResumeMainSingleObserver<T> extends AtomicReference<Disposable>
      implements SingleObserver<T>, Disposable {
          private static final long serialVersionUID = -5314538511045349925L;
  
          final SingleObserver<? super T> downstream;
  
          final Function<? super Throwable, ? extends SingleSource<? extends T>> nextFunction;
  
          ResumeMainSingleObserver(SingleObserver<? super T> actual,
                  Function<? super Throwable, ? extends SingleSource<? extends T>> nextFunction) {
              this.downstream = actual;
              this.nextFunction = nextFunction;
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              if (DisposableHelper.setOnce(this, d)) {
                  downstream.onSubscribe(this);
              }
          }
  
          @Override
          public void onSuccess(T value) {
              downstream.onSuccess(value);
          }
  
          @Override
          public void onError(Throwable e) {
              SingleSource<? extends T> source;
  
              try {
                  source = Objects.requireNonNull(nextFunction.apply(e), "The nextFunction returned a null SingleSource.");
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  downstream.onError(new CompositeException(e, ex));
                  return;
              }
  
              source.subscribe(new ResumeSingleObserver<T>(this, downstream));
          }
  
          @Override
          public void dispose() {
              DisposableHelper.dispose(this);
          }
  
          @Override
          public boolean isDisposed() {
              return DisposableHelper.isDisposed(get());
          }
      }
  }
  