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 static org.mockito.ArgumentMatchers.*;
  import static org.mockito.Mockito.*;
  
  import java.util.*;
  import java.util.concurrent.CopyOnWriteArrayList;
  import java.util.concurrent.atomic.*;
  
  import org.junit.*;
  import org.reactivestreams.*;
  
  import io.reactivex.rxjava3.core.*;
  import io.reactivex.rxjava3.exceptions.*;
  import io.reactivex.rxjava3.flowable.*;
  import io.reactivex.rxjava3.flowable.FlowableEventStream.Event;
  import io.reactivex.rxjava3.functions.*;
  import io.reactivex.rxjava3.plugins.RxJavaPlugins;
  import io.reactivex.rxjava3.processors.PublishProcessor;
  import io.reactivex.rxjava3.subscribers.*;
  import io.reactivex.rxjava3.testsupport.*;
  
  public class FlowableScanTest extends RxJavaTest {
  
      @Test
      public void scanIntegersWithInitialValue() {
          Subscriber<String> subscriber = TestHelper.mockSubscriber();
  
          Flowable<Integer> flowable = Flowable.just(1, 2, 3);
  
          Flowable<String> m = flowable.scan("", new BiFunction<String, Integer, String>() {
  
              @Override
              public String apply(String s, Integer n) {
                  return s + n.toString();
              }
  
          });
          m.subscribe(subscriber);
  
          verify(subscriber, never()).onError(any(Throwable.class));
          verify(subscriber, times(1)).onNext("");
          verify(subscriber, times(1)).onNext("1");
          verify(subscriber, times(1)).onNext("12");
          verify(subscriber, times(1)).onNext("123");
          verify(subscriber, times(4)).onNext(anyString());
          verify(subscriber, times(1)).onComplete();
          verify(subscriber, never()).onError(any(Throwable.class));
      }
  
      @Test
      public void scanIntegersWithoutInitialValue() {
          Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
  
          Flowable<Integer> flowable = Flowable.just(1, 2, 3);
  
          Flowable<Integer> m = flowable.scan(new BiFunction<Integer, Integer, Integer>() {
  
              @Override
              public Integer apply(Integer t1, Integer t2) {
                  return t1 + t2;
              }
  
          });
          m.subscribe(subscriber);
  
          verify(subscriber, never()).onError(any(Throwable.class));
          verify(subscriber, never()).onNext(0);
          verify(subscriber, times(1)).onNext(1);
          verify(subscriber, times(1)).onNext(3);
          verify(subscriber, times(1)).onNext(6);
          verify(subscriber, times(3)).onNext(anyInt());
          verify(subscriber, times(1)).onComplete();
          verify(subscriber, never()).onError(any(Throwable.class));
      }
  
      @Test
      public void scanIntegersWithoutInitialValueAndOnlyOneValue() {
          Subscriber<Integer> subscriber = TestHelper.mockSubscriber();
  
          Flowable<Integer> flowable = Flowable.just(1);
  
          Flowable<Integer> m = flowable.scan(new BiFunction<Integer, Integer, Integer>() {
  
              @Override
              public Integer apply(Integer t1, Integer t2) {
                  return t1 + t2;
              }
  
          });
          m.subscribe(subscriber);
  
          verify(subscriber, never()).onError(any(Throwable.class));
          verify(subscriber, never()).onNext(0);
          verify(subscriber, times(1)).onNext(1);
          verify(subscriber, times(1)).onNext(anyInt());
          verify(subscriber, times(1)).onComplete();
          verify(subscriber, never()).onError(any(Throwable.class));
      }
  
      @Test
      public void shouldNotEmitUntilAfterSubscription() {
          TestSubscriber<Integer> ts = new TestSubscriber<>();
          Flowable.range(1, 100).scan(0, new BiFunction<Integer, Integer, Integer>() {
  
              @Override
              public Integer apply(Integer t1, Integer t2) {
                  return t1 + t2;
              }
  
          }).filter(new Predicate<Integer>() {
  
              @Override
              public boolean test(Integer t1) {
                  // this will cause request(1) when 0 is emitted
                  return t1 > 0;
              }
  
          }).subscribe(ts);
  
          assertEquals(100, ts.values().size());
      }
  
      @Test
      public void backpressureWithInitialValue() {
          final AtomicInteger count = new AtomicInteger();
          Flowable.range(1, 100)
                  .scan(0, new BiFunction<Integer, Integer, Integer>() {
  
                      @Override
                      public Integer apply(Integer t1, Integer t2) {
                          return t1 + t2;
                      }
  
                  })
                  .subscribe(new DefaultSubscriber<Integer>() {
  
                      @Override
                      public void onStart() {
                          request(10);
                      }
  
                      @Override
                      public void onComplete() {
  
                      }
  
                      @Override
                      public void onError(Throwable e) {
                          Assert.fail(e.getMessage());
                          e.printStackTrace();
                      }
  
                      @Override
                      public void onNext(Integer t) {
                          count.incrementAndGet();
                      }
  
                  });
  
          // we only expect to receive 10 since we request(10)
          assertEquals(10, count.get());
      }
  
      @Test
      public void backpressureWithoutInitialValue() {
          final AtomicInteger count = new AtomicInteger();
          Flowable.range(1, 100)
                  .scan(new BiFunction<Integer, Integer, Integer>() {
  
                      @Override
                      public Integer apply(Integer t1, Integer t2) {
                          return t1 + t2;
                      }
  
                  })
                  .subscribe(new DefaultSubscriber<Integer>() {
  
                      @Override
                      public void onStart() {
                          request(10);
                      }
  
                      @Override
                      public void onComplete() {
  
                      }
  
                      @Override
                      public void onError(Throwable e) {
                          Assert.fail(e.getMessage());
                          e.printStackTrace();
                      }
  
                      @Override
                      public void onNext(Integer t) {
                          count.incrementAndGet();
                      }
  
                  });
  
          // we only expect to receive 10 since we request(10)
          assertEquals(10, count.get());
      }
  
      @Test
      public void noBackpressureWithInitialValue() {
          final AtomicInteger count = new AtomicInteger();
          Flowable.range(1, 100)
                  .scan(0, new BiFunction<Integer, Integer, Integer>() {
  
                      @Override
                      public Integer apply(Integer t1, Integer t2) {
                          return t1 + t2;
                      }
  
                  })
                  .subscribe(new DefaultSubscriber<Integer>() {
  
                      @Override
                      public void onComplete() {
  
                      }
  
                      @Override
                      public void onError(Throwable e) {
                          Assert.fail(e.getMessage());
                          e.printStackTrace();
                      }
  
                      @Override
                      public void onNext(Integer t) {
                          count.incrementAndGet();
                      }
  
                  });
  
          // we only expect to receive 101 as we'll receive all 100 + the initial value
          assertEquals(101, count.get());
      }
  
      /**
       * This uses the public API collect which uses scan under the covers.
       */
      @Test
      public void seedFactory() {
          Single<List<Integer>> o = Flowable.range(1, 10)
                  .collect(new Supplier<List<Integer>>() {
  
                      @Override
                      public List<Integer> get() {
                          return new ArrayList<>();
                      }
  
                  }, new BiConsumer<List<Integer>, Integer>() {
  
                      @Override
                      public void accept(List<Integer> list, Integer t2) {
                          list.add(t2);
                      }
  
                  });
  
          assertEquals(Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10), o.blockingGet());
          assertEquals(Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10), o.blockingGet());
      }
  
      /**
       * This uses the public API collect which uses scan under the covers.
       */
      @Test
      public void seedFactoryFlowable() {
          Flowable<List<Integer>> f = Flowable.range(1, 10)
                  .collect(new Supplier<List<Integer>>() {
  
                      @Override
                      public List<Integer> get() {
                          return new ArrayList<>();
                      }
  
                  }, new BiConsumer<List<Integer>, Integer>() {
  
                      @Override
                      public void accept(List<Integer> list, Integer t2) {
                          list.add(t2);
                      }
  
                  }).toFlowable().takeLast(1);
  
          assertEquals(Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10), f.blockingSingle());
          assertEquals(Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9, 10), f.blockingSingle());
      }
  
      @Test
      public void scanWithRequestOne() {
          Flowable<Integer> f = Flowable.just(1, 2).scan(0, new BiFunction<Integer, Integer, Integer>() {
  
              @Override
              public Integer apply(Integer t1, Integer t2) {
                  return t1 + t2;
              }
  
          }).take(1);
          TestSubscriberEx<Integer> subscriber = new TestSubscriberEx<>();
          f.subscribe(subscriber);
          subscriber.assertValue(0);
          subscriber.assertTerminated();
          subscriber.assertNoErrors();
      }
  
      @Test
      public void scanShouldNotRequestZero() {
          final AtomicReference<Subscription> producer = new AtomicReference<>();
          Flowable<Integer> f = Flowable.unsafeCreate(new Publisher<Integer>() {
              @Override
              public void subscribe(final Subscriber<? super Integer> subscriber) {
                  Subscription p = spy(new Subscription() {
  
                      private AtomicBoolean requested = new AtomicBoolean(false);
  
                      @Override
                      public void request(long n) {
                          if (requested.compareAndSet(false, true)) {
                              subscriber.onNext(1);
                              subscriber.onComplete();
                          }
                      }
  
                      @Override
                      public void cancel() {
  
                      }
                  });
                  producer.set(p);
                  subscriber.onSubscribe(p);
              }
          }).scan(100, new BiFunction<Integer, Integer, Integer>() {
  
              @Override
              public Integer apply(Integer t1, Integer t2) {
                  return t1 + t2;
              }
  
          });
  
          f.subscribe(new TestSubscriber<Integer>(1L) {
  
              @Override
              public void onNext(Integer integer) {
                  request(1);
              }
          });
  
          verify(producer.get(), never()).request(0);
          verify(producer.get(), times(1)).request(Flowable.bufferSize() - 1);
      }
  
      @Test
      public void dispose() {
          TestHelper.checkDisposed(PublishProcessor.create().scan(new BiFunction<Object, Object, Object>() {
              @Override
              public Object apply(Object a, Object b) throws Exception {
                  return a;
              }
          }));
  
          TestHelper.checkDisposed(PublishProcessor.<Integer>create().scan(0, new BiFunction<Integer, Integer, Integer>() {
              @Override
              public Integer apply(Integer a, Integer b) throws Exception {
                  return a + b;
              }
          }));
      }
  
      @Test
      public void doubleOnSubscribe() {
          TestHelper.checkDoubleOnSubscribeFlowable(new Function<Flowable<Object>, Flowable<Object>>() {
              @Override
              public Flowable<Object> apply(Flowable<Object> f) throws Exception {
                  return f.scan(new BiFunction<Object, Object, Object>() {
                      @Override
                      public Object apply(Object a, Object b) throws Exception {
                          return a;
                      }
                  });
              }
          });
  
          TestHelper.checkDoubleOnSubscribeFlowable(new Function<Flowable<Object>, Flowable<Object>>() {
              @Override
              public Flowable<Object> apply(Flowable<Object> f) throws Exception {
                  return f.scan(0, new BiFunction<Object, Object, Object>() {
                      @Override
                      public Object apply(Object a, Object b) throws Exception {
                          return a;
                      }
                  });
              }
          });
      }
  
      @Test
      public void error() {
          Flowable.error(new TestException())
          .scan(new BiFunction<Object, Object, Object>() {
              @Override
              public Object apply(Object a, Object b) throws Exception {
                  return a;
              }
          })
          .test()
          .assertFailure(TestException.class);
      }
  
      @Test
      public void neverSource() {
          Flowable.<Integer>never()
          .scan(0, new BiFunction<Integer, Integer, Integer>() {
              @Override
              public Integer apply(Integer a, Integer b) throws Exception {
                  return a + b;
              }
          })
          .test()
          .assertValue(0)
          .assertNoErrors()
          .assertNotComplete();
      }
  
      @Test
      public void unsubscribeScan() {
  
          FlowableEventStream.getEventStream("HTTP-ClusterB", 20)
          .scan(new HashMap<>(), new BiFunction<HashMap<String, String>, Event, HashMap<String, String>>() {
              @Override
              public HashMap<String, String> apply(HashMap<String, String> accum, Event perInstanceEvent) {
                  accum.put("instance", perInstanceEvent.instanceId);
                  return accum;
              }
          })
          .take(10)
          .blockingForEach(new Consumer<HashMap<String, String>>() {
              @Override
              public void accept(HashMap<String, String> v) {
                  System.out.println(v);
              }
          });
      }
  
      @Test
      public void scanWithSeedDoesNotEmitErrorTwiceIfScanFunctionThrows() {
          final List<Throwable> list = new CopyOnWriteArrayList<>();
          Consumer<Throwable> errorConsumer = new Consumer<Throwable>() {
              @Override
              public void accept(Throwable t) throws Exception {
                   list.add(t);
              }};
          try {
              RxJavaPlugins.setErrorHandler(errorConsumer);
              final RuntimeException e = new RuntimeException();
              final RuntimeException e2 = new RuntimeException();
              Burst.items(1).error(e2)
                .scan(0, throwingBiFunction(e))
                .test()
                .assertValues(0)
                .assertError(e);
  
              assertEquals("" + list, 1, list.size());
              assertTrue("" + list, list.get(0) instanceof UndeliverableException);
              assertEquals(e2, list.get(0).getCause());
          } finally {
              RxJavaPlugins.reset();
          }
      }
  
      @Test
      public void scanWithSeedDoesNotEmitTerminalEventTwiceIfScanFunctionThrows() {
          final RuntimeException e = new RuntimeException();
          Burst.item(1).create()
            .scan(0, throwingBiFunction(e))
            .test()
            .assertValue(0)
            .assertError(e);
      }
  
      @Test
      public void scanWithSeedDoesNotProcessOnNextAfterTerminalEventIfScanFunctionThrows() {
          final RuntimeException e = new RuntimeException();
          final AtomicInteger count = new AtomicInteger();
          Burst.items(1, 2).create().scan(0, new BiFunction<Integer, Integer, Integer>() {
  
              @Override
              public Integer apply(Integer n1, Integer n2) throws Exception {
                  count.incrementAndGet();
                  throw e;
              }})
            .test()
            .assertValues(0)
            .assertError(e);
          assertEquals(1, count.get());
      }
  
      @Test
      public void scanWithSeedCompletesNormally() {
          Flowable.just(1, 2, 3).scan(0, SUM)
            .test()
            .assertValues(0, 1, 3, 6)
            .assertComplete();
      }
  
      @Test
      public void scanWithSeedWhenScanSeedProviderThrows() {
          final RuntimeException e = new RuntimeException();
          Flowable.just(1, 2, 3).scanWith(throwingSupplier(e),
              SUM)
            .test()
            .assertError(e)
            .assertNoValues();
      }
  
      @Test
      public void scanNoSeed() {
          Flowable.just(1, 2, 3)
             .scan(SUM)
             .test()
             .assertValues(1, 3, 6)
             .assertComplete();
      }
  
      @Test
      public void scanNoSeedDoesNotEmitErrorTwiceIfScanFunctionThrows() {
          final List<Throwable> list = new CopyOnWriteArrayList<>();
          Consumer<Throwable> errorConsumer = new Consumer<Throwable>() {
              @Override
              public void accept(Throwable t) throws Exception {
                   list.add(t);
              }};
          try {
              RxJavaPlugins.setErrorHandler(errorConsumer);
              final RuntimeException e = new RuntimeException();
              final RuntimeException e2 = new RuntimeException();
              Burst.items(1, 2).error(e2)
                .scan(throwingBiFunction(e))
                .test()
                .assertValue(1)
                .assertError(e);
  
              assertEquals("" + list, 1, list.size());
              assertTrue("" + list, list.get(0) instanceof UndeliverableException);
              assertEquals(e2, list.get(0).getCause());
          } finally {
              RxJavaPlugins.reset();
          }
      }
  
      @Test
      public void scanNoSeedDoesNotEmitTerminalEventTwiceIfScanFunctionThrows() {
          final RuntimeException e = new RuntimeException();
          Burst.items(1, 2).create()
            .scan(throwingBiFunction(e))
            .test()
            .assertValue(1)
            .assertError(e);
      }
  
      @Test
      public void scanNoSeedDoesNotProcessOnNextAfterTerminalEventIfScanFunctionThrows() {
          final RuntimeException e = new RuntimeException();
          final AtomicInteger count = new AtomicInteger();
          Burst.items(1, 2, 3).create().scan(new BiFunction<Integer, Integer, Integer>() {
  
              @Override
              public Integer apply(Integer n1, Integer n2) throws Exception {
                  count.incrementAndGet();
                  throw e;
              }})
            .test()
            .assertValue(1)
            .assertError(e);
          assertEquals(1, count.get());
      }
  
      private static BiFunction<Integer, Integer, Integer> throwingBiFunction(final RuntimeException e) {
          return new BiFunction<Integer, Integer, Integer>() {
              @Override
              public Integer apply(Integer n1, Integer n2) throws Exception {
                  throw e;
              }
          };
      }
  
      private static final BiFunction<Integer, Integer, Integer> SUM = new BiFunction<Integer, Integer, Integer>() {
  
          @Override
          public Integer apply(Integer t1, Integer t2) throws Exception {
              return t1 + t2;
          }
      };
  
      private static Supplier<Integer> throwingSupplier(final RuntimeException e) {
          return new Supplier<Integer>() {
              @Override
              public Integer get() throws Exception {
                  throw e;
              }
          };
      }
  
      @Test
      public void scanEmptyBackpressured() {
          Flowable.<Integer>empty()
          .scan(0, SUM)
          .test(1)
          .assertResult(0);
      }
  
      @Test
      public void scanErrorBackpressured() {
          Flowable.<Integer>error(new TestException())
          .scan(0, SUM)
          .test(0)
          .assertFailure(TestException.class);
      }
  
      @Test
      public void scanTake() {
          TestSubscriber<Integer> ts = new TestSubscriber<Integer>() {
              @Override
              public void onNext(Integer t) {
                  super.onNext(t);
                  onComplete();
                  cancel();
              }
          };
  
          Flowable.range(1, 10)
          .scan(0, SUM)
          .subscribe(ts)
          ;
  
          ts.assertResult(0);
      }
  
      @Test
      public void scanLong() {
          int n = 2 * Flowable.bufferSize();
  
          for (int b = 1; b <= n; b *= 2) {
              List<Integer> list = Flowable.range(1, n)
              .scan(0, new BiFunction<Integer, Integer, Integer>() {
                  @Override
                  public Integer apply(Integer a, Integer b) throws Exception {
                      return b;
                  }
              })
              .rebatchRequests(b)
              .toList()
              .blockingGet();
  
              for (int i = 0; i <= n; i++) {
                  assertEquals(i, list.get(i).intValue());
              }
          }
      }
  
      @Test
      public void badRequest() {
          TestHelper.assertBadRequestReported(Flowable.<Integer>never().scanWith(() -> 1, (a, b) -> a + b));
      }
  
      @Test
      public void drainMoreWork() {
          PublishProcessor<Integer> pp = PublishProcessor.create();
  
          TestSubscriber<Integer> ts = pp.scanWith(() -> 0, (a, b) -> a + b)
          .doOnNext(v -> {
              if (v == 1) {
                  pp.onNext(2);
                  pp.onComplete();
              }
          })
          .test();
  
          pp.onNext(1);
  
          ts.assertResult(0, 1, 3);
      }
  }
  