content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 com.datastax.oss.driver.internal.core.util.concurrent;
  
  import static com.datastax.oss.driver.Assertions.assertThat;
  import static org.mockito.Mockito.any;
  import static org.mockito.Mockito.anyLong;
  import static org.mockito.Mockito.eq;
  import static org.mockito.Mockito.inOrder;
  import static org.mockito.Mockito.never;
  import static org.mockito.Mockito.times;
  import static org.mockito.Mockito.verify;
  import static org.mockito.Mockito.when;
  
  import com.datastax.oss.driver.shaded.guava.common.base.Joiner;
  import io.netty.util.concurrent.EventExecutor;
  import io.netty.util.concurrent.ScheduledFuture;
  import java.time.Duration;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.concurrent.TimeUnit;
  import org.junit.Before;
  import org.junit.Test;
  import org.mockito.ArgumentCaptor;
  import org.mockito.InOrder;
  import org.mockito.Mock;
  import org.mockito.MockitoAnnotations;
  
  public class DebouncerTest {
  
    private static final Duration DEFAULT_WINDOW = Duration.ofSeconds(1);
    private static final int DEFAULT_MAX_EVENTS = 10;
  
    @Mock private EventExecutor adminExecutor;
    @Mock private ScheduledFuture<?> scheduledFuture;
    private List<String> results;
  
    @Before
    public void setup() {
      MockitoAnnotations.initMocks(this);
      when(adminExecutor.inEventLoop()).thenReturn(true);
      when(adminExecutor.schedule(
              any(Runnable.class), eq(DEFAULT_WINDOW.toNanos()), eq(TimeUnit.NANOSECONDS)))
          .thenAnswer((i) -> scheduledFuture);
      results = new ArrayList<>();
    }
  
    private String coalesce(List<Integer> events) {
      return Joiner.on(",").join(events);
    }
  
    private void flush(String result) {
      results.add(result);
    }
  
    @Test
    public void should_flush_synchronously_if_window_is_zero() {
      Debouncer<Integer, String> debouncer =
          new Debouncer<>(
              adminExecutor, this::coalesce, this::flush, Duration.ZERO, DEFAULT_MAX_EVENTS);
  
      debouncer.receive(1);
      debouncer.receive(2);
  
      verify(adminExecutor, never()).schedule(any(Runnable.class), anyLong(), any(TimeUnit.class));
  
      assertThat(results).containsExactly("1", "2");
    }
  
    @Test
    public void should_flush_synchronously_if_max_events_is_one() {
      Debouncer<Integer, String> debouncer =
          new Debouncer<>(adminExecutor, this::coalesce, this::flush, DEFAULT_WINDOW, 1);
  
      debouncer.receive(1);
      debouncer.receive(2);
  
      verify(adminExecutor, never()).schedule(any(Runnable.class), anyLong(), any(TimeUnit.class));
  
      assertThat(results).containsExactly("1", "2");
    }
  
    @Test
    public void should_debounce_after_time_window_if_no_other_event() {
      Debouncer<Integer, String> debouncer =
          new Debouncer<>(
              adminExecutor, this::coalesce, this::flush, DEFAULT_WINDOW, DEFAULT_MAX_EVENTS);
      debouncer.receive(1);
  
      // a task should have been scheduled, run it
      ArgumentCaptor<Runnable> captor = ArgumentCaptor.forClass(Runnable.class);
      verify(adminExecutor)
          .schedule(captor.capture(), eq(DEFAULT_WINDOW.toNanos()), eq(TimeUnit.NANOSECONDS));
      captor.getValue().run();
  
      // the element should have been flushed
      assertThat(results).containsExactly("1");
    }
  
    @Test
    public void should_reset_time_window_when_new_event() {
      Debouncer<Integer, String> debouncer =
          new Debouncer<>(
              adminExecutor, this::coalesce, this::flush, DEFAULT_WINDOW, DEFAULT_MAX_EVENTS);
      debouncer.receive(1);
      debouncer.receive(2);
  
      InOrder inOrder = inOrder(adminExecutor, scheduledFuture);
  
      // a first task should have been scheduled, and then cancelled
      inOrder
          .verify(adminExecutor)
          .schedule(any(Runnable.class), eq(DEFAULT_WINDOW.toNanos()), eq(TimeUnit.NANOSECONDS));
      inOrder.verify(scheduledFuture).cancel(true);
  
      // a second task should have been scheduled, run it
      ArgumentCaptor<Runnable> captor = ArgumentCaptor.forClass(Runnable.class);
      inOrder
          .verify(adminExecutor)
          .schedule(captor.capture(), eq(DEFAULT_WINDOW.toNanos()), eq(TimeUnit.NANOSECONDS));
      captor.getValue().run();
  
      // both elements should have been flushed together
      assertThat(results).containsExactly("1,2");
    }
  
    @Test
    public void should_force_flush_after_max_events() {
      Debouncer<Integer, String> debouncer =
          new Debouncer<>(
              adminExecutor, this::coalesce, this::flush, DEFAULT_WINDOW, DEFAULT_MAX_EVENTS);
      for (int i = 0; i < 10; i++) {
        debouncer.receive(i);
      }
      verify(adminExecutor, times(9))
          .schedule(any(Runnable.class), eq(DEFAULT_WINDOW.toNanos()), eq(TimeUnit.NANOSECONDS));
      verify(scheduledFuture, times(9)).cancel(true);
      assertThat(results).containsExactly("0,1,2,3,4,5,6,7,8,9");
    }
  
    @Test
    public void should_cancel_next_flush_when_stopped() {
      Debouncer<Integer, String> debouncer =
          new Debouncer<>(
              adminExecutor, this::coalesce, this::flush, DEFAULT_WINDOW, DEFAULT_MAX_EVENTS);
  
      debouncer.receive(1);
      verify(adminExecutor)
          .schedule(any(Runnable.class), eq(DEFAULT_WINDOW.toNanos()), eq(TimeUnit.NANOSECONDS));
  
      debouncer.stop();
      verify(scheduledFuture).cancel(true);
    }
  
    @Test
    public void should_ignore_new_events_when_flushed() {
      Debouncer<Integer, String> debouncer =
          new Debouncer<>(
              adminExecutor, this::coalesce, this::flush, DEFAULT_WINDOW, DEFAULT_MAX_EVENTS);
      debouncer.stop();
  
      debouncer.receive(1);
      verify(adminExecutor, never())
          .schedule(any(Runnable.class), eq(DEFAULT_WINDOW.toNanos()), eq(TimeUnit.NANOSECONDS));
    }
  }
  