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.assertEquals;
  import static org.mockito.ArgumentMatchers.any;
  import static org.mockito.Mockito.*;
  
  import java.util.*;
  import java.util.concurrent.TimeUnit;
  import java.util.concurrent.atomic.AtomicInteger;
  
  import org.junit.Test;
  import org.mockito.InOrder;
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.annotations.NonNull;
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.exceptions.TestException;
  import io.reactivex.rxjava3.functions.*;
  import io.reactivex.rxjava3.schedulers.Schedulers;
  import io.reactivex.rxjava3.subscribers.*;
  import io.reactivex.rxjava3.testsupport.TestHelper;
  
  public class FlowableTakeLastTest extends RxJavaTest {
  
      @Test
      public void takeLastEmpty() {
          Flowable<String> w = Flowable.empty();
          Flowable<String> take = w.takeLast(2);
  
          Subscriber<String> subscriber = TestHelper.mockSubscriber();
          take.subscribe(subscriber);
  
          verify(subscriber, never()).onNext(any(String.class));
          verify(subscriber, never()).onError(any(Throwable.class));
          verify(subscriber, times(1)).onComplete();
      }
  
      @Test
      public void takeLast1() {
          Flowable<String> w = Flowable.just("one", "two", "three");
          Flowable<String> take = w.takeLast(2);
  
          Subscriber<String> subscriber = TestHelper.mockSubscriber();
          InOrder inOrder = inOrder(subscriber);
          take.subscribe(subscriber);
  
          inOrder.verify(subscriber, times(1)).onNext("two");
          inOrder.verify(subscriber, times(1)).onNext("three");
          verify(subscriber, never()).onNext("one");
          verify(subscriber, never()).onError(any(Throwable.class));
          verify(subscriber, times(1)).onComplete();
      }
  
      @Test
      public void takeLast2() {
          Flowable<String> w = Flowable.just("one");
          Flowable<String> take = w.takeLast(10);
  
          Subscriber<String> subscriber = TestHelper.mockSubscriber();
          take.subscribe(subscriber);
  
          verify(subscriber, times(1)).onNext("one");
          verify(subscriber, never()).onError(any(Throwable.class));
          verify(subscriber, times(1)).onComplete();
      }
  
      @Test
      public void takeLastWithZeroCount() {
          Flowable<String> w = Flowable.just("one");
          Flowable<String> take = w.takeLast(0);
  
          Subscriber<String> subscriber = TestHelper.mockSubscriber();
          take.subscribe(subscriber);
  
          verify(subscriber, never()).onNext("one");
          verify(subscriber, never()).onError(any(Throwable.class));
          verify(subscriber, times(1)).onComplete();
      }
  
      @Test(expected = IllegalArgumentException.class)
      public void takeLastWithNegativeCount() {
          Flowable.just("one").takeLast(-1);
      }
  
      @Test
      public void backpressure1() {
          TestSubscriber<Integer> ts = new TestSubscriber<>();
          Flowable.range(1, 100000).takeLast(1)
          .observeOn(Schedulers.newThread())
          .map(newSlowProcessor()).subscribe(ts);
          ts.awaitDone(5, TimeUnit.SECONDS);
          ts.assertNoErrors();
          ts.assertValue(100000);
      }
  
      @Test
      public void backpressure2() {
          TestSubscriber<Integer> ts = new TestSubscriber<>();
          Flowable.range(1, 100000).takeLast(Flowable.bufferSize() * 4)
          .observeOn(Schedulers.newThread()).map(newSlowProcessor()).subscribe(ts);
          ts.awaitDone(5, TimeUnit.SECONDS);
          ts.assertNoErrors();
          assertEquals(Flowable.bufferSize() * 4, ts.values().size());
      }
  
      private Function<Integer, Integer> newSlowProcessor() {
          return new Function<Integer, Integer>() {
              int c;
  
              @Override
              public Integer apply(Integer i) {
                  if (c++ < 100) {
                      try {
                          Thread.sleep(1);
                      } catch (InterruptedException e) {
                      }
                  }
                  return i;
              }
  
          };
      }
  
      @Test
      public void issue1522() {
          // https://github.com/ReactiveX/RxJava/issues/1522
          assertEquals(0, Flowable
                  .empty()
                  .count()
                  .toFlowable()
                  .filter(new Predicate<Long>() {
                      @Override
                      public boolean test(Long v) {
                          return false;
                      }
                  })
                  .toList()
                  .blockingGet().size());
      }
  
      @Test
      public void ignoreRequest1() {
          // If `takeLast` does not ignore `request` properly, StackOverflowError will be thrown.
          Flowable.range(0, 100000).takeLast(100000).subscribe(new DefaultSubscriber<Integer>() {
  
              @Override
              public void onStart() {
                  request(Long.MAX_VALUE);
              }
  
              @Override
              public void onComplete() {
  
              }
  
              @Override
              public void onError(Throwable e) {
              }
  
              @Override
              public void onNext(Integer integer) {
                  request(Long.MAX_VALUE);
              }
          });
      }
  
      @Test
      public void ignoreRequest2() {
          // If `takeLast` does not ignore `request` properly, StackOverflowError will be thrown.
          Flowable.range(0, 100000).takeLast(100000).subscribe(new DefaultSubscriber<Integer>() {
  
              @Override
              public void onStart() {
                  request(1);
              }
  
              @Override
              public void onComplete() {
              }
  
              @Override
              public void onError(Throwable e) {
              }
  
              @Override
              public void onNext(Integer integer) {
                  request(1);
              }
          });
      }
  
      @Test
      public void ignoreRequest3() {
          // If `takeLast` does not ignore `request` properly, it will enter an infinite loop.
          Flowable.range(0, 100000).takeLast(100000).subscribe(new DefaultSubscriber<Integer>() {
  
              @Override
              public void onStart() {
                  request(1);
              }
  
              @Override
              public void onComplete() {
  
              }
  
              @Override
              public void onError(Throwable e) {
              }
  
              @Override
              public void onNext(Integer integer) {
                  request(Long.MAX_VALUE);
              }
          });
      }
  
      @Test
      public void ignoreRequest4() {
          // If `takeLast` does not ignore `request` properly, StackOverflowError will be thrown.
          Flowable.range(0, 100000).takeLast(100000).subscribe(new DefaultSubscriber<Integer>() {
  
              @Override
              public void onStart() {
                  request(Long.MAX_VALUE);
              }
  
              @Override
              public void onComplete() {
  
              }
  
              @Override
              public void onError(Throwable e) {
              }
  
              @Override
              public void onNext(Integer integer) {
                  request(1);
              }
          });
      }
  
      @Test
      public void unsubscribeTakesEffectEarlyOnFastPath() {
          final AtomicInteger count = new AtomicInteger();
          Flowable.range(0, 100000).takeLast(100000).subscribe(new DefaultSubscriber<Integer>() {
  
              @Override
              public void onStart() {
                  request(Long.MAX_VALUE);
              }
  
              @Override
              public void onComplete() {
  
              }
  
              @Override
              public void onError(Throwable e) {
              }
  
              @Override
              public void onNext(Integer integer) {
                  count.incrementAndGet();
                  cancel();
              }
          });
          assertEquals(1, count.get());
      }
  
      @Test
      public void requestOverflow() {
          final List<Integer> list = new ArrayList<>();
          Flowable.range(1, 100).takeLast(50).subscribe(new DefaultSubscriber<Integer>() {
  
              @Override
              public void onStart() {
                  request(2);
              }
  
              @Override
              public void onComplete() {
  
              }
  
              @Override
              public void onError(Throwable e) {
  
              }
  
              @Override
              public void onNext(Integer t) {
                  list.add(t);
                  request(Long.MAX_VALUE - 1);
              }});
          assertEquals(50, list.size());
      }
  
      @Test
      public void dispose() {
          TestHelper.checkDisposed(Flowable.range(1, 10).takeLast(5));
      }
  
      @Test
      public void doubleOnSubscribe() {
          TestHelper.checkDoubleOnSubscribeFlowable(new Function<Flowable<Object>, Flowable<Object>>() {
              @Override
              public Flowable<Object> apply(Flowable<Object> f) throws Exception {
                  return f.takeLast(5);
              }
          });
      }
  
      @Test
      public void error() {
          Flowable.error(new TestException())
          .takeLast(5)
          .test()
          .assertFailure(TestException.class);
      }
  
      @Test
      public void takeLastTake() {
          Flowable.range(1, 10)
          .takeLast(5)
          .take(2)
          .test()
          .assertResult(6, 7);
      }
  
      @Test
      public void badRequest() {
          TestHelper.assertBadRequestReported(Flowable.never().takeLast(2));
      }
  
      @Test
      public void cancelThenRequest() {
          Flowable.never().takeLast(2)
          .subscribe(new FlowableSubscriber<Object>() {
  
              @Override
              public void onNext(@NonNull Object t) {
              }
  
              @Override
              public void onError(Throwable t) {
              }
  
              @Override
              public void onComplete() {
              }
  
              @Override
              public void onSubscribe(@NonNull Subscription s) {
                  s.cancel();
                  s.request(1);
              }
          });
      }
  
      @Test
      public void noRequestEmpty() {
          Flowable.empty()
          .takeLast(2)
          .test(0L)
          .assertResult();
      }
  
      @Test
      public void moreValuesRemainingThanRequested() {
          Flowable.range(1, 4)
          .takeLast(3)
          .test(0L)
          .assertEmpty()
          .requestMore(2)
          .assertValuesOnly(2, 3)
          .requestMore(2)
          .assertResult(2, 3, 4);
      }
  }
  