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.pool;
  
  import static com.datastax.oss.driver.Assertions.assertThat;
  import static org.mockito.Mockito.never;
  import static org.mockito.Mockito.verify;
  import static org.mockito.Mockito.when;
  
  import com.datastax.oss.driver.internal.core.channel.DriverChannel;
  import org.junit.Before;
  import org.junit.Test;
  import org.mockito.Mock;
  import org.mockito.MockitoAnnotations;
  
  public class ChannelSetTest {
    @Mock private DriverChannel channel1, channel2, channel3;
    private ChannelSet set;
  
    @Before
    public void setup() {
      MockitoAnnotations.initMocks(this);
      set = new ChannelSet();
    }
  
    @Test
    public void should_return_null_when_empty() {
      assertThat(set.size()).isEqualTo(0);
      assertThat(set.next()).isNull();
    }
  
    @Test
    public void should_return_element_when_single() {
      // Given
      when(channel1.preAcquireId()).thenReturn(true);
  
      // When
      set.add(channel1);
  
      // Then
      assertThat(set.size()).isEqualTo(1);
      assertThat(set.next()).isEqualTo(channel1);
      verify(channel1, never()).getAvailableIds();
      verify(channel1).preAcquireId();
    }
  
    @Test
    public void should_return_null_when_single_but_full() {
      // Given
      when(channel1.preAcquireId()).thenReturn(false);
  
      // When
      set.add(channel1);
  
      // Then
      assertThat(set.next()).isNull();
      verify(channel1).preAcquireId();
    }
  
    @Test
    public void should_return_most_available_when_multiple() {
      // Given
      when(channel1.getAvailableIds()).thenReturn(2);
      when(channel2.getAvailableIds()).thenReturn(12);
      when(channel3.getAvailableIds()).thenReturn(8);
      when(channel2.preAcquireId()).thenReturn(true);
  
      // When
      set.add(channel1);
      set.add(channel2);
      set.add(channel3);
  
      // Then
      assertThat(set.size()).isEqualTo(3);
      assertThat(set.next()).isEqualTo(channel2);
      verify(channel1).getAvailableIds();
      verify(channel2).getAvailableIds();
      verify(channel3).getAvailableIds();
      verify(channel2).preAcquireId();
  
      // When
      when(channel1.getAvailableIds()).thenReturn(15);
      when(channel1.preAcquireId()).thenReturn(true);
  
      // Then
      assertThat(set.next()).isEqualTo(channel1);
      verify(channel1).preAcquireId();
    }
  
    @Test
    public void should_return_null_when_multiple_but_all_full() {
      // Given
      when(channel1.getAvailableIds()).thenReturn(0);
      when(channel2.getAvailableIds()).thenReturn(0);
      when(channel3.getAvailableIds()).thenReturn(0);
  
      // When
      set.add(channel1);
      set.add(channel2);
      set.add(channel3);
  
      // Then
      assertThat(set.next()).isNull();
    }
  
    @Test
    public void should_remove_channels() {
      // Given
      when(channel1.getAvailableIds()).thenReturn(2);
      when(channel2.getAvailableIds()).thenReturn(12);
      when(channel3.getAvailableIds()).thenReturn(8);
      when(channel2.preAcquireId()).thenReturn(true);
  
      set.add(channel1);
      set.add(channel2);
      set.add(channel3);
      assertThat(set.next()).isEqualTo(channel2);
  
      // When
      set.remove(channel2);
      when(channel3.preAcquireId()).thenReturn(true);
  
      // Then
      assertThat(set.size()).isEqualTo(2);
      assertThat(set.next()).isEqualTo(channel3);
  
      // When
      set.remove(channel3);
      when(channel1.preAcquireId()).thenReturn(true);
  
      // Then
      assertThat(set.size()).isEqualTo(1);
      assertThat(set.next()).isEqualTo(channel1);
  
      // When
      set.remove(channel1);
  
      // Then
      assertThat(set.size()).isEqualTo(0);
      assertThat(set.next()).isNull();
    }
  
    /**
     * Check that {@link ChannelSet#next()} doesn't spin forever if it keeps racing (see comments in
     * the implementation).
     */
    @Test
    public void should_not_loop_indefinitely_if_acquisition_keeps_failing() {
      // Given
      when(channel1.getAvailableIds()).thenReturn(2);
      when(channel2.getAvailableIds()).thenReturn(12);
      when(channel3.getAvailableIds()).thenReturn(8);
      // channel2 is the most available but we keep failing to acquire (simulating the race condition)
      when(channel2.preAcquireId()).thenReturn(false);
  
      // When
      set.add(channel1);
      set.add(channel2);
      set.add(channel3);
  
      // Then
      assertThat(set.next()).isNull();
    }
  }
  