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.completable;
  
  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;
  
  public final class CompletableAmb extends Completable {
      private final CompletableSource[] sources;
      private final Iterable<? extends CompletableSource> sourcesIterable;
  
      public CompletableAmb(CompletableSource[] sources, Iterable<? extends CompletableSource> sourcesIterable) {
          this.sources = sources;
          this.sourcesIterable = sourcesIterable;
      }
  
      @Override
      public void subscribeActual(final CompletableObserver observer) {
          CompletableSource[] sources = this.sources;
          int count = 0;
          if (sources == null) {
              sources = new CompletableSource[8];
              try {
                  for (CompletableSource element : sourcesIterable) {
                      if (element == null) {
                          EmptyDisposable.error(new NullPointerException("One of the sources is null"), observer);
                          return;
                      }
                      if (count == sources.length) {
                          CompletableSource[] b = new CompletableSource[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;
          }
  
          final CompositeDisposable set = new CompositeDisposable();
          observer.onSubscribe(set);
  
          final AtomicBoolean once = new AtomicBoolean();
  
          for (int i = 0; i < count; i++) {
              CompletableSource c = sources[i];
              if (set.isDisposed()) {
                  return;
              }
              if (c == null) {
                  NullPointerException npe = new NullPointerException("One of the sources is null");
                  if (once.compareAndSet(false, true)) {
                      set.dispose();
                      observer.onError(npe);
                  } else {
                      RxJavaPlugins.onError(npe);
                  }
                  return;
              }
  
              // no need to have separate subscribers because inner is stateless
              c.subscribe(new Amb(once, set, observer));
          }
  
          if (count == 0) {
              observer.onComplete();
          }
      }
  
      static final class Amb implements CompletableObserver {
  
          final AtomicBoolean once;
  
          final CompositeDisposable set;
  
          final CompletableObserver downstream;
  
          Disposable upstream;
  
          Amb(AtomicBoolean once, CompositeDisposable set, CompletableObserver observer) {
              this.once = once;
              this.set = set;
              this.downstream = observer;
          }
  
          @Override
          public void onComplete() {
              if (once.compareAndSet(false, true)) {
                  set.delete(upstream);
                  set.dispose();
                  downstream.onComplete();
              }
          }
  
          @Override
          public void onError(Throwable e) {
              if (once.compareAndSet(false, true)) {
                  set.delete(upstream);
                  set.dispose();
                  downstream.onError(e);
              } else {
                  RxJavaPlugins.onError(e);
              }
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              upstream = d;
              set.add(d);
          }
      }
  }
  