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.mixed;
  
  import java.util.Objects;
  import java.util.concurrent.atomic.AtomicReference;
  
  import org.reactivestreams.Subscription;
  
  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;
  import io.reactivex.rxjava3.internal.subscriptions.SubscriptionHelper;
  import io.reactivex.rxjava3.internal.util.AtomicThrowable;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  /**
   * Maps the upstream values into {@link CompletableSource}s, subscribes to the newer one while
   * disposing the subscription to the previous {@code CompletableSource}, thus keeping at most one
   * active {@code CompletableSource} running.
   * <p>History: 2.1.11 - experimental
   * @param <T> the upstream value type
   * @since 2.2
   */
  public final class FlowableSwitchMapCompletable<T> extends Completable {
  
      final Flowable<T> source;
  
      final Function<? super T, ? extends CompletableSource> mapper;
  
      final boolean delayErrors;
  
      public FlowableSwitchMapCompletable(Flowable<T> source,
              Function<? super T, ? extends CompletableSource> mapper, boolean delayErrors) {
          this.source = source;
          this.mapper = mapper;
          this.delayErrors = delayErrors;
      }
  
      @Override
      protected void subscribeActual(CompletableObserver observer) {
          source.subscribe(new SwitchMapCompletableObserver<>(observer, mapper, delayErrors));
      }
  
      static final class SwitchMapCompletableObserver<T> implements FlowableSubscriber<T>, Disposable {
  
          final CompletableObserver downstream;
  
          final Function<? super T, ? extends CompletableSource> mapper;
  
          final boolean delayErrors;
  
          final AtomicThrowable errors;
  
          final AtomicReference<SwitchMapInnerObserver> inner;
  
          static final SwitchMapInnerObserver INNER_DISPOSED = new SwitchMapInnerObserver(null);
  
          volatile boolean done;
  
          Subscription upstream;
  
          SwitchMapCompletableObserver(CompletableObserver downstream,
                  Function<? super T, ? extends CompletableSource> mapper, boolean delayErrors) {
              this.downstream = downstream;
              this.mapper = mapper;
              this.delayErrors = delayErrors;
              this.errors = new AtomicThrowable();
              this.inner = new AtomicReference<>();
          }
  
          @Override
          public void onSubscribe(Subscription s) {
              if (SubscriptionHelper.validate(upstream, s)) {
                  this.upstream = s;
                  downstream.onSubscribe(this);
                  s.request(Long.MAX_VALUE);
              }
          }
  
          @Override
          public void onNext(T t) {
              CompletableSource c;
  
              try {
                  c = Objects.requireNonNull(mapper.apply(t), "The mapper returned a null CompletableSource");
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  upstream.cancel();
                  onError(ex);
                  return;
              }
  
              SwitchMapInnerObserver o = new SwitchMapInnerObserver(this);
  
              for (;;) {
                  SwitchMapInnerObserver current = inner.get();
                  if (current == INNER_DISPOSED) {
                      break;
                  }
                  if (inner.compareAndSet(current, o)) {
                      if (current != null) {
                          current.dispose();
                      }
                      c.subscribe(o);
                      break;
                  }
              }
          }
  
          @Override
          public void onError(Throwable t) {
              if (errors.tryAddThrowableOrReport(t)) {
                  if (delayErrors) {
                      onComplete();
                  } else {
                      disposeInner();
                      errors.tryTerminateConsumer(downstream);
                  }
              }
          }
  
          @Override
          public void onComplete() {
              done = true;
              if (inner.get() == null) {
                  errors.tryTerminateConsumer(downstream);
              }
          }
  
          void disposeInner() {
              SwitchMapInnerObserver o = inner.getAndSet(INNER_DISPOSED);
              if (o != null && o != INNER_DISPOSED) {
                  o.dispose();
              }
          }
  
          @Override
          public void dispose() {
              upstream.cancel();
              disposeInner();
              errors.tryTerminateAndReport();
          }
  
          @Override
          public boolean isDisposed() {
              return inner.get() == INNER_DISPOSED;
          }
  
          void innerError(SwitchMapInnerObserver sender, Throwable error) {
              if (inner.compareAndSet(sender, null)) {
                  if (errors.tryAddThrowableOrReport(error)) {
                      if (delayErrors) {
                          if (done) {
                              errors.tryTerminateConsumer(downstream);
                          }
                      } else {
                          upstream.cancel();
                          disposeInner();
                          errors.tryTerminateConsumer(downstream);
                      }
                  }
              } else {
                  RxJavaPlugins.onError(error);
              }
          }
  
          void innerComplete(SwitchMapInnerObserver sender) {
              if (inner.compareAndSet(sender, null)) {
                  if (done) {
                      errors.tryTerminateConsumer(downstream);
                  }
              }
          }
  
          static final class SwitchMapInnerObserver extends AtomicReference<Disposable>
          implements CompletableObserver {
  
              private static final long serialVersionUID = -8003404460084760287L;
  
              final SwitchMapCompletableObserver<?> parent;
  
              SwitchMapInnerObserver(SwitchMapCompletableObserver<?> parent) {
                  this.parent = parent;
              }
  
              @Override
              public void onSubscribe(Disposable d) {
                  DisposableHelper.setOnce(this, d);
              }
  
              @Override
              public void onError(Throwable e) {
                  parent.innerError(this, e);
              }
  
              @Override
              public void onComplete() {
                  parent.innerComplete(this);
              }
  
              void dispose() {
                  DisposableHelper.dispose(this);
              }
          }
      }
  }
  