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.flowable;
  
  import java.util.Objects;
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.annotations.Nullable;
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.*;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.functions.Function;
  import io.reactivex.rxjava3.internal.disposables.DisposableHelper;
  import io.reactivex.rxjava3.internal.subscriptions.*;
  import io.reactivex.rxjava3.internal.util.AtomicThrowable;
  
  /**
   * Maps a sequence of values into CompletableSources and awaits their termination.
   * @param <T> the value type
   */
  public final class FlowableFlatMapCompletable<T> extends AbstractFlowableWithUpstream<T, T> {
  
      final Function<? super T, ? extends CompletableSource> mapper;
  
      final int maxConcurrency;
  
      final boolean delayErrors;
  
      public FlowableFlatMapCompletable(Flowable<T> source,
              Function<? super T, ? extends CompletableSource> mapper, boolean delayErrors,
              int maxConcurrency) {
          super(source);
          this.mapper = mapper;
          this.delayErrors = delayErrors;
          this.maxConcurrency = maxConcurrency;
      }
  
      @Override
      protected void subscribeActual(Subscriber<? super T> subscriber) {
          source.subscribe(new FlatMapCompletableMainSubscriber<>(subscriber, mapper, delayErrors, maxConcurrency));
      }
  
      static final class FlatMapCompletableMainSubscriber<T> extends BasicIntQueueSubscription<T>
      implements FlowableSubscriber<T> {
          private static final long serialVersionUID = 8443155186132538303L;
  
          final Subscriber<? super T> downstream;
  
          final AtomicThrowable errors;
  
          final Function<? super T, ? extends CompletableSource> mapper;
  
          final boolean delayErrors;
  
          final CompositeDisposable set;
  
          final int maxConcurrency;
  
          Subscription upstream;
  
          volatile boolean cancelled;
  
          FlatMapCompletableMainSubscriber(Subscriber<? super T> subscriber,
                  Function<? super T, ? extends CompletableSource> mapper, boolean delayErrors,
                  int maxConcurrency) {
              this.downstream = subscriber;
              this.mapper = mapper;
              this.delayErrors = delayErrors;
              this.errors = new AtomicThrowable();
              this.set = new CompositeDisposable();
              this.maxConcurrency = maxConcurrency;
              this.lazySet(1);
          }
  
          @Override
          public void onSubscribe(Subscription s) {
              if (SubscriptionHelper.validate(this.upstream, s)) {
                  this.upstream = s;
  
                  downstream.onSubscribe(this);
  
                  int m = maxConcurrency;
                  if (m == Integer.MAX_VALUE) {
                      s.request(Long.MAX_VALUE);
                  } else {
                      s.request(m);
                  }
              }
          }
  
          @Override
          public void onNext(T value) {
              CompletableSource cs;
  
              try {
                  cs = Objects.requireNonNull(mapper.apply(value), "The mapper returned a null CompletableSource");
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  upstream.cancel();
                  onError(ex);
                  return;
              }
  
              getAndIncrement();
  
              InnerConsumer inner = new InnerConsumer();
  
              if (!cancelled && set.add(inner)) {
                  cs.subscribe(inner);
              }
          }
  
          @Override
          public void onError(Throwable e) {
              if (errors.tryAddThrowableOrReport(e)) {
                  if (delayErrors) {
                      if (decrementAndGet() == 0) {
                          errors.tryTerminateConsumer(downstream);
                      } else {
                          if (maxConcurrency != Integer.MAX_VALUE) {
                              upstream.request(1);
                          }
                      }
                  } else {
                      cancelled = true;
                      upstream.cancel();
                      set.dispose();
                      errors.tryTerminateConsumer(downstream);
                  }
              }
          }
  
          @Override
          public void onComplete() {
              if (decrementAndGet() == 0) {
                  errors.tryTerminateConsumer(downstream);
              } else {
                  if (maxConcurrency != Integer.MAX_VALUE) {
                      upstream.request(1);
                  }
              }
          }
  
          @Override
          public void cancel() {
              cancelled = true;
              upstream.cancel();
              set.dispose();
              errors.tryTerminateAndReport();
          }
  
          @Override
          public void request(long n) {
              // ignored, no values emitted
          }
  
          @Nullable
          @Override
          public T poll() {
              return null; // always empty
          }
  
          @Override
          public boolean isEmpty() {
              return true; // always empty
          }
  
          @Override
          public void clear() {
              // nothing to clear
          }
  
          @Override
          public int requestFusion(int mode) {
              return mode & ASYNC;
          }
  
          void innerComplete(InnerConsumer inner) {
              set.delete(inner);
              onComplete();
          }
  
          void innerError(InnerConsumer inner, Throwable e) {
              set.delete(inner);
              onError(e);
          }
  
          final class InnerConsumer extends AtomicReference<Disposable> implements CompletableObserver, Disposable {
              private static final long serialVersionUID = 8606673141535671828L;
  
              @Override
              public void onSubscribe(Disposable d) {
                  DisposableHelper.setOnce(this, d);
              }
  
              @Override
              public void onComplete() {
                  innerComplete(this);
              }
  
              @Override
              public void onError(Throwable e) {
                  innerError(this, e);
              }
  
              @Override
              public void dispose() {
                  DisposableHelper.dispose(this);
              }
  
              @Override
              public boolean isDisposed() {
                  return DisposableHelper.isDisposed(get());
              }
          }
      }
  }
  