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.flowable;
  
  import static org.junit.Assert.*;
  
  import java.util.Arrays;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import org.junit.Test;
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.functions.Consumer;
  import io.reactivex.rxjava3.internal.subscriptions.BooleanSubscription;
  import io.reactivex.rxjava3.schedulers.Schedulers;
  import io.reactivex.rxjava3.subscribers.*;
  
  public class FlowableSwitchIfEmptyTest extends RxJavaTest {
  
      @Test
      public void switchWhenNotEmpty() throws Exception {
          final AtomicBoolean subscribed = new AtomicBoolean(false);
          final Flowable<Integer> flowable = Flowable.just(4)
                  .switchIfEmpty(Flowable.just(2)
                  .doOnSubscribe(new Consumer<Subscription>() {
                      @Override
                      public void accept(Subscription s) {
                          subscribed.set(true);
                      }
                  }));
  
          assertEquals(4, flowable.blockingSingle().intValue());
          assertFalse(subscribed.get());
      }
  
      @Test
      public void switchWhenEmpty() throws Exception {
          final Flowable<Integer> flowable = Flowable.<Integer>empty()
                  .switchIfEmpty(Flowable.fromIterable(Arrays.asList(42)));
  
          assertEquals(42, flowable.blockingSingle().intValue());
      }
  
      @Test
      public void switchWithProducer() throws Exception {
          final AtomicBoolean emitted = new AtomicBoolean(false);
          Flowable<Long> withProducer = Flowable.unsafeCreate(new Publisher<Long>() {
              @Override
              public void subscribe(final Subscriber<? super Long> subscriber) {
                  subscriber.onSubscribe(new Subscription() {
                      @Override
                      public void request(long n) {
                          if (n > 0 && emitted.compareAndSet(false, true)) {
                              emitted.set(true);
                              subscriber.onNext(42L);
                              subscriber.onComplete();
                          }
                      }
  
                      @Override
                      public void cancel() {
  
                      }
                  });
              }
          });
  
          final Flowable<Long> flowable = Flowable.<Long>empty().switchIfEmpty(withProducer);
          assertEquals(42, flowable.blockingSingle().intValue());
      }
  
      @Test
      public void switchTriggerUnsubscribe() throws Exception {
  
          final BooleanSubscription bs = new BooleanSubscription();
  
          Flowable<Long> withProducer = Flowable.unsafeCreate(new Publisher<Long>() {
              @Override
              public void subscribe(final Subscriber<? super Long> subscriber) {
                  subscriber.onSubscribe(bs);
                  subscriber.onNext(42L);
              }
          });
  
          Flowable.<Long>empty()
                  .switchIfEmpty(withProducer)
                  .lift(new FlowableOperator<Long, Long>() {
              @Override
              public Subscriber<? super Long> apply(final Subscriber<? super Long> child) {
                  return new DefaultSubscriber<Long>() {
                      @Override
                      public void onComplete() {
  
                      }
  
                      @Override
                      public void onError(Throwable e) {
  
                      }
  
                      @Override
                      public void onNext(Long aLong) {
                          cancel();
                      }
  
                  };
              }
          }).subscribe();
  
          assertTrue(bs.isCancelled());
          // FIXME no longer assertable
  //        assertTrue(sub.isUnsubscribed());
      }
  
      @Test
      public void switchShouldNotTriggerUnsubscribe() {
          final BooleanSubscription bs = new BooleanSubscription();
  
          Flowable.unsafeCreate(new Publisher<Long>() {
              @Override
              public void subscribe(final Subscriber<? super Long> subscriber) {
                  subscriber.onSubscribe(bs);
                  subscriber.onComplete();
              }
          }).switchIfEmpty(Flowable.<Long>never()).subscribe();
          assertFalse(bs.isCancelled());
      }
  
      @Test
      public void switchRequestAlternativeObservableWithBackpressure() {
  
          TestSubscriber<Integer> ts = new TestSubscriber<>(1L);
  
          Flowable.<Integer>empty().switchIfEmpty(Flowable.just(1, 2, 3)).subscribe(ts);
  
          assertEquals(Arrays.asList(1), ts.values());
          ts.assertNoErrors();
          ts.request(1);
          ts.assertValueCount(2);
          ts.request(1);
          ts.assertValueCount(3);
      }
  
      @Test
      public void backpressureNoRequest() {
          TestSubscriber<Integer> ts = new TestSubscriber<>(0L);
          Flowable.<Integer>empty().switchIfEmpty(Flowable.just(1, 2, 3)).subscribe(ts);
          ts.assertNoValues();
          ts.assertNoErrors();
      }
  
      @Test
      public void backpressureOnFirstObservable() {
          TestSubscriber<Integer> ts = new TestSubscriber<>(0L);
          Flowable.just(1, 2, 3).switchIfEmpty(Flowable.just(4, 5, 6)).subscribe(ts);
          ts.assertNotComplete();
          ts.assertNoErrors();
          ts.assertNoValues();
      }
  
      @Test
      public void requestsNotLost() throws InterruptedException {
          final TestSubscriber<Long> ts = new TestSubscriber<>(0L);
          Flowable.unsafeCreate(new Publisher<Long>() {
  
              @Override
              public void subscribe(final Subscriber<? super Long> subscriber) {
                  subscriber.onSubscribe(new Subscription() {
                      final AtomicBoolean completed = new AtomicBoolean(false);
                      @Override
                      public void request(long n) {
                          if (n > 0 && completed.compareAndSet(false, true)) {
                              Schedulers.io().createWorker().schedule(new Runnable() {
                                  @Override
                                  public void run() {
                                      subscriber.onComplete();
                                  }}, 100, TimeUnit.MILLISECONDS);
                          }
                      }
  
                      @Override
                      public void cancel() {
  
                      }
                  });
              }})
            .switchIfEmpty(Flowable.fromIterable(Arrays.asList(1L, 2L, 3L)))
            .subscribeOn(Schedulers.computation())
            .subscribe(ts);
  
          Thread.sleep(50);
          //request while first observable is still finishing (as empty)
          ts.request(1);
          ts.request(1);
          Thread.sleep(500);
          ts.assertNotComplete();
          ts.assertNoErrors();
          ts.assertValueCount(2);
          ts.cancel();
      }
  }
  