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.observable;
  
  import java.util.Iterator;
  import java.util.Objects;
  
  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.plugins.RxJavaPlugins;
  
  /**
   * Maps a sequence into an Iterable and emits its values.
   *
   * @param <T> the input value type to map to Iterable
   * @param <R> the element type of the Iterable and the output
   */
  public final class ObservableFlattenIterable<T, R> extends AbstractObservableWithUpstream<T, R> {
  
      final Function<? super T, ? extends Iterable<? extends R>> mapper;
  
      public ObservableFlattenIterable(ObservableSource<T> source,
              Function<? super T, ? extends Iterable<? extends R>> mapper) {
          super(source);
          this.mapper = mapper;
      }
  
      @Override
      protected void subscribeActual(Observer<? super R> observer) {
          source.subscribe(new FlattenIterableObserver<>(observer, mapper));
      }
  
      static final class FlattenIterableObserver<T, R> implements Observer<T>, Disposable {
          final Observer<? super R> downstream;
  
          final Function<? super T, ? extends Iterable<? extends R>> mapper;
  
          Disposable upstream;
  
          FlattenIterableObserver(Observer<? super R> actual, Function<? super T, ? extends Iterable<? extends R>> mapper) {
              this.downstream = actual;
              this.mapper = mapper;
          }
  
          @Override
          public void onSubscribe(Disposable d) {
              if (DisposableHelper.validate(this.upstream, d)) {
                  this.upstream = d;
  
                  downstream.onSubscribe(this);
              }
          }
  
          @Override
          public void onNext(T value) {
              if (upstream == DisposableHelper.DISPOSED) {
                  return;
              }
  
              Iterator<? extends R> it;
  
              try {
                  it = mapper.apply(value).iterator();
              } catch (Throwable ex) {
                  Exceptions.throwIfFatal(ex);
                  upstream.dispose();
                  onError(ex);
                  return;
              }
  
              Observer<? super R> a = downstream;
  
              for (;;) {
                  boolean b;
  
                  try {
                      b = it.hasNext();
                  } catch (Throwable ex) {
                      Exceptions.throwIfFatal(ex);
                      upstream.dispose();
                      onError(ex);
                      return;
                  }
  
                  if (b) {
                      R v;
  
                      try {
                          v = Objects.requireNonNull(it.next(), "The iterator returned a null value");
                      } catch (Throwable ex) {
                          Exceptions.throwIfFatal(ex);
                          upstream.dispose();
                          onError(ex);
                          return;
                      }
  
                      a.onNext(v);
                  } else {
                      break;
                  }
              }
          }
  
          @Override
          public void onError(Throwable e) {
              if (upstream == DisposableHelper.DISPOSED) {
                  RxJavaPlugins.onError(e);
                  return;
              }
              upstream = DisposableHelper.DISPOSED;
              downstream.onError(e);
          }
  
          @Override
          public void onComplete() {
              if (upstream == DisposableHelper.DISPOSED) {
                  return;
              }
              upstream = DisposableHelper.DISPOSED;
              downstream.onComplete();
          }
  
          @Override
          public boolean isDisposed() {
              return upstream.isDisposed();
          }
  
          @Override
          public void dispose() {
              upstream.dispose();
              upstream = DisposableHelper.DISPOSED;
          }
      }
  }
  