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.maybe;
  
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.*;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.internal.disposables.EmptyDisposable;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  
  /**
   * Signals the event of the first MaybeSource that signals.
   *
   * @param <T> the value type emitted
   */
  public final class MaybeAmb<T> extends Maybe<T> {
      private final MaybeSource<? extends T>[] sources;
      private final Iterable<? extends MaybeSource<? extends T>> sourcesIterable;
  
      public MaybeAmb(MaybeSource<? extends T>[] sources, Iterable<? extends MaybeSource<? extends T>> sourcesIterable) {
          this.sources = sources;
          this.sourcesIterable = sourcesIterable;
      }
  
      @Override
      @SuppressWarnings("unchecked")
      protected void subscribeActual(MaybeObserver<? super T> observer) {
          MaybeSource<? extends T>[] sources = this.sources;
          int count = 0;
          if (sources == null) {
              sources = new MaybeSource[8];
              try {
                  for (MaybeSource<? extends T> element : sourcesIterable) {
                      if (element == null) {
                          EmptyDisposable.error(new NullPointerException("One of the sources is null"), observer);
                          return;
                      }
                      if (count == sources.length) {
                          MaybeSource<? extends T>[] b = new MaybeSource[count + (count >> 2)];
                          System.arraycopy(sources, 0, b, 0, count);
                          sources = b;
                      }
                      sources[count++] = element;
                  }
              } catch (Throwable e) {
                  Exceptions.throwIfFatal(e);
                  EmptyDisposable.error(e, observer);
                  return;
              }
          } else {
              count = sources.length;
          }
  
          CompositeDisposable set = new CompositeDisposable();
          observer.onSubscribe(set);
  
          AtomicBoolean winner = new AtomicBoolean();
  
          for (int i = 0; i < count; i++) {
              MaybeSource<? extends T> s = sources[i];
              if (set.isDisposed()) {
                  return;
              }
  
              if (s == null) {
                  set.dispose();
                  NullPointerException ex = new NullPointerException("One of the MaybeSources is null");
                  if (winner.compareAndSet(false, true)) {
                      observer.onError(ex);
                  } else {
                      RxJavaPlugins.onError(ex);
                  }
                  return;
              }
  
              s.subscribe(new AmbMaybeObserver<T>(observer, set, winner));
          }
  
          if (count == 0) {
              observer.onComplete();
          }
      }
  
      static final class AmbMaybeObserver<T>
      implements MaybeObserver<T> {
  
          final MaybeObserver<? super T> downstream;
  
          final AtomicBoolean winner;
  
          final CompositeDisposable set;
  
          Disposable upstream;
  
          AmbMaybeObserver(MaybeObserver<? super T> downstream, CompositeDisposable set, AtomicBoolean winner) {
              this.downstream = downstream;
              this.set = set;
              this.winner = winner;
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              upstream = d;
              set.add(d);
          }
  
          @Override
          public void onSuccess(T value) {
              if (winner.compareAndSet(false, true)) {
                  set.delete(upstream);
                  set.dispose();
  
                  downstream.onSuccess(value);
              }
          }
  
          @Override
          public void onError(Throwable e) {
              if (winner.compareAndSet(false, true)) {
                  set.delete(upstream);
                  set.dispose();
  
                  downstream.onError(e);
              } else {
                  RxJavaPlugins.onError(e);
              }
          }
  
          @Override
          public void onComplete() {
              if (winner.compareAndSet(false, true)) {
                  set.delete(upstream);
                  set.dispose();
  
                  downstream.onComplete();
              }
          }
      }
  }
  