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.Iterator;
  import java.util.Objects;
  import java.util.concurrent.atomic.AtomicInteger;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.disposables.Disposable;
  import io.reactivex.rxjava3.exceptions.Exceptions;
  import io.reactivex.rxjava3.internal.disposables.*;
  
  public final class CompletableConcatIterable extends Completable {
      final Iterable<? extends CompletableSource> sources;
  
      public CompletableConcatIterable(Iterable<? extends CompletableSource> sources) {
          this.sources = sources;
      }
  
      @Override
      public void subscribeActual(CompletableObserver observer) {
  
          Iterator<? extends CompletableSource> it;
  
          try {
              it = Objects.requireNonNull(sources.iterator(), "The iterator returned is null");
          } catch (Throwable e) {
              Exceptions.throwIfFatal(e);
              EmptyDisposable.error(e, observer);
              return;
          }
  
          ConcatInnerObserver inner = new ConcatInnerObserver(observer, it);
          observer.onSubscribe(inner.sd);
          inner.next();
      }
  
      static final class ConcatInnerObserver extends AtomicInteger implements CompletableObserver {
  
          private static final long serialVersionUID = -7965400327305809232L;
  
          final CompletableObserver downstream;
          final Iterator<? extends CompletableSource> sources;
  
          final SequentialDisposable sd;
  
          ConcatInnerObserver(CompletableObserver actual, Iterator<? extends CompletableSource> sources) {
              this.downstream = actual;
              this.sources = sources;
              this.sd = new SequentialDisposable();
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              sd.replace(d);
          }
  
          @Override
          public void onError(Throwable e) {
              downstream.onError(e);
          }
  
          @Override
          public void onComplete() {
              next();
          }
  
          void next() {
              if (sd.isDisposed()) {
                  return;
              }
  
              if (getAndIncrement() != 0) {
                  return;
              }
  
              Iterator<? extends CompletableSource> a = sources;
              do {
                  if (sd.isDisposed()) {
                      return;
                  }
  
                  boolean b;
                  try {
                      b = a.hasNext();
                  } catch (Throwable ex) {
                      Exceptions.throwIfFatal(ex);
                      downstream.onError(ex);
                      return;
                  }
  
                  if (!b) {
                      downstream.onComplete();
                      return;
                  }
  
                  CompletableSource c;
  
                  try {
                      c = Objects.requireNonNull(a.next(), "The CompletableSource returned is null");
                  } catch (Throwable ex) {
                      Exceptions.throwIfFatal(ex);
                      downstream.onError(ex);
                      return;
                  }
  
                  c.subscribe(this);
              } while (decrementAndGet() != 0);
          }
      }
  }
  