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.*;
  
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.exceptions.*;
  import io.reactivex.rxjava3.functions.Function;
  import io.reactivex.rxjava3.internal.subscribers.*;
  import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
  import io.reactivex.rxjava3.internal.util.*;
  import io.reactivex.rxjava3.operators.SimpleQueue;
  import io.reactivex.rxjava3.operators.SpscLinkedArrayQueue;
  
  public final class FlowableConcatMapEager<T, R> extends AbstractFlowableWithUpstream<T, R> {
  
      final Function<? super T, ? extends Publisher<? extends R>> mapper;
  
      final int maxConcurrency;
  
      final int prefetch;
  
      final ErrorMode errorMode;
  
      public FlowableConcatMapEager(Flowable<T> source,
              Function<? super T, ? extends Publisher<? extends R>> mapper,
              int maxConcurrency,
              int prefetch,
              ErrorMode errorMode) {
          super(source);
          this.mapper = mapper;
          this.maxConcurrency = maxConcurrency;
          this.prefetch = prefetch;
          this.errorMode = errorMode;
      }
  
      @Override
      protected void subscribeActual(Subscriber<? super R> s) {
          source.subscribe(new ConcatMapEagerDelayErrorSubscriber<>(
                  s, mapper, maxConcurrency, prefetch, errorMode));
      }
  
      static final class ConcatMapEagerDelayErrorSubscriber<T, R>
      extends AtomicInteger
      implements FlowableSubscriber<T>, Subscription, InnerQueuedSubscriberSupport<R> {
  
          private static final long serialVersionUID = -4255299542215038287L;
  
          final Subscriber<? super R> downstream;
  
          final Function<? super T, ? extends Publisher<? extends R>> mapper;
  
          final int maxConcurrency;
  
          final int prefetch;
  
          final ErrorMode errorMode;
  
          final AtomicThrowable errors;
  
          final AtomicLong requested;
  
          final SpscLinkedArrayQueue<InnerQueuedSubscriber<R>> subscribers;
  
          Subscription upstream;
  
          volatile boolean cancelled;
  
          volatile boolean done;
  
          volatile InnerQueuedSubscriber<R> current;
  
          ConcatMapEagerDelayErrorSubscriber(Subscriber<? super R> actual,
                  Function<? super T, ? extends Publisher<? extends R>> mapper, int maxConcurrency, int prefetch,
                  ErrorMode errorMode) {
              this.downstream = actual;
              this.mapper = mapper;
              this.maxConcurrency = maxConcurrency;
              this.prefetch = prefetch;
              this.errorMode = errorMode;
              this.subscribers = new SpscLinkedArrayQueue<>(Math.min(prefetch, maxConcurrency));
              this.errors = new AtomicThrowable();
              this.requested = new AtomicLong();
          }
  
          @Override
          public void onSubscribe(Subscription s) {
              if (SubscriptionHelper.validate(this.upstream, s)) {
                  this.upstream = s;
  
                  downstream.onSubscribe(this);
  
                  s.request(maxConcurrency == Integer.MAX_VALUE ? Long.MAX_VALUE : maxConcurrency);
              }
  
          }
  
          @Override
          public void onNext(T t) {
              Publisher<? extends R> p;
  
              try {
                  p = Objects.requireNonNull(mapper.apply(t), "The mapper returned a null Publisher");
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  upstream.cancel();
                  onError(ex);
                  return;
              }
  
              InnerQueuedSubscriber<R> inner = new InnerQueuedSubscriber<>(this, prefetch);
  
              if (cancelled) {
                  return;
              }
  
              subscribers.offer(inner);
  
              p.subscribe(inner);
  
              if (cancelled) {
                  inner.cancel();
                  drainAndCancel();
              }
          }
  
          @Override
          public void onError(Throwable t) {
              if (errors.tryAddThrowableOrReport(t)) {
                  done = true;
                  drain();
              }
          }
  
          @Override
          public void onComplete() {
              done = true;
              drain();
          }
  
          @Override
          public void cancel() {
              if (cancelled) {
                  return;
              }
              cancelled = true;
              upstream.cancel();
              errors.tryTerminateAndReport();
  
              drainAndCancel();
          }
  
          void drainAndCancel() {
              if (getAndIncrement() == 0) {
                  do {
                      cancelAll();
                  } while (decrementAndGet() != 0);
              }
          }
  
          void cancelAll() {
              InnerQueuedSubscriber<R> inner = current;
              current = null;
  
              if (inner != null) {
                  inner.cancel();
              }
  
              while ((inner = subscribers.poll()) != null) {
                  inner.cancel();
              }
          }
  
          @Override
          public void request(long n) {
              if (SubscriptionHelper.validate(n)) {
                  BackpressureHelper.add(requested, n);
                  drain();
              }
          }
  
          @Override
          public void innerNext(InnerQueuedSubscriber<R> inner, R value) {
              if (inner.queue().offer(value)) {
                  drain();
              } else {
                  inner.cancel();
                  innerError(inner, MissingBackpressureException.createDefault());
              }
          }
  
          @Override
          public void innerError(InnerQueuedSubscriber<R> inner, Throwable e) {
              if (errors.tryAddThrowableOrReport(e)) {
                  inner.setDone();
                  if (errorMode != ErrorMode.END) {
                      upstream.cancel();
                  }
                  drain();
              }
          }
  
          @Override
          public void innerComplete(InnerQueuedSubscriber<R> inner) {
              inner.setDone();
              drain();
          }
  
          @Override
          public void drain() {
              if (getAndIncrement() != 0) {
                  return;
              }
  
              int missed = 1;
              InnerQueuedSubscriber<R> inner = current;
              Subscriber<? super R> a = downstream;
              ErrorMode em = errorMode;
  
              for (;;) {
                  long r = requested.get();
                  long e = 0L;
  
                  if (inner == null) {
  
                      if (em != ErrorMode.END) {
                          Throwable ex = errors.get();
                          if (ex != null) {
                              cancelAll();
  
                              errors.tryTerminateConsumer(downstream);
                              return;
                          }
                      }
  
                      boolean outerDone = done;
  
                      inner = subscribers.poll();
  
                      if (outerDone && inner == null) {
                          errors.tryTerminateConsumer(downstream);
                          return;
                      }
  
                      if (inner != null) {
                          current = inner;
                      }
                  }
  
                  boolean continueNextSource = false;
  
                  if (inner != null) {
                      SimpleQueue<R> q = inner.queue();
                      if (q != null) {
                          while (e != r) {
                              if (cancelled) {
                                  cancelAll();
                                  return;
                              }
  
                              if (em == ErrorMode.IMMEDIATE) {
                                  Throwable ex = errors.get();
                                  if (ex != null) {
                                      current = null;
                                      inner.cancel();
                                      cancelAll();
  
                                      errors.tryTerminateConsumer(downstream);
                                      return;
                                  }
                              }
  
                              boolean d = inner.isDone();
  
                              R v;
  
                              try {
                                  v = q.poll();
                              } catch (Throwable ex) {
                                  Exceptions.throwIfFatal(ex);
                                  current = null;
                                  inner.cancel();
                                  cancelAll();
                                  a.onError(ex);
                                  return;
                              }
  
                              boolean empty = v == null;
  
                              if (d && empty) {
                                  inner = null;
                                  current = null;
                                  upstream.request(1);
                                  continueNextSource = true;
                                  break;
                              }
  
                              if (empty) {
                                  break;
                              }
  
                              a.onNext(v);
  
                              e++;
  
                              inner.request(1L);
                          }
  
                          if (e == r) {
                              if (cancelled) {
                                  cancelAll();
                                  return;
                              }
  
                              if (em == ErrorMode.IMMEDIATE) {
                                  Throwable ex = errors.get();
                                  if (ex != null) {
                                      current = null;
                                      inner.cancel();
                                      cancelAll();
  
                                      errors.tryTerminateConsumer(downstream);
                                      return;
                                  }
                              }
  
                              boolean d = inner.isDone();
  
                              boolean empty = q.isEmpty();
  
                              if (d && empty) {
                                  inner = null;
                                  current = null;
                                  upstream.request(1);
                                  continueNextSource = true;
                              }
                          }
                      }
                  }
  
                  if (e != 0L && r != Long.MAX_VALUE) {
                      requested.addAndGet(-e);
                  }
  
                  if (continueNextSource) {
                      continue;
                  }
  
                  missed = addAndGet(-missed);
                  if (missed == 0) {
                      break;
                  }
              }
          }
      }
  }
  