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   * 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 org.apache.kafka.common.replica;
  
  import org.apache.kafka.common.Node;
  import org.apache.kafka.common.TopicPartition;
  import org.apache.kafka.common.security.auth.KafkaPrincipal;
  
  import org.junit.jupiter.api.Test;
  
  import java.net.InetAddress;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Optional;
  import java.util.Set;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  import static org.apache.kafka.test.TestUtils.assertOptional;
  import static org.junit.jupiter.api.Assertions.assertEquals;
  
  public class ReplicaSelectorTest {
  
      @Test
      public void testSameRackSelector() {
          TopicPartition tp = new TopicPartition("test", 0);
  
          List<ReplicaView> replicaViewSet = replicaInfoSet();
          ReplicaView leader = replicaViewSet.get(0);
          PartitionView partitionView = partitionInfo(new HashSet<>(replicaViewSet), leader);
  
          ReplicaSelector selector = new RackAwareReplicaSelector();
          Optional<ReplicaView> selected = selector.select(tp, metadata("rack-b"), partitionView);
          assertOptional(selected, replicaInfo -> {
              assertEquals(replicaInfo.endpoint().rack(), "rack-b", "Expect replica to be in rack-b");
              assertEquals(replicaInfo.endpoint().id(), 3, "Expected replica 3 since it is more caught-up");
          });
  
          selected = selector.select(tp, metadata("not-a-rack"), partitionView);
          assertOptional(selected, replicaInfo ->
              assertEquals(replicaInfo, leader, "Expect leader when we can't find any nodes in given rack")
          );
  
          selected = selector.select(tp, metadata("rack-a"), partitionView);
          assertOptional(selected, replicaInfo -> {
              assertEquals(replicaInfo.endpoint().rack(), "rack-a", "Expect replica to be in rack-a");
              assertEquals(replicaInfo, leader, "Expect the leader since it's in rack-a");
          });
  
  
      }
  
      static List<ReplicaView> replicaInfoSet() {
          return Stream.of(
                  replicaInfo(new Node(0, "host0", 1234, "rack-a"), 4, 0),
                  replicaInfo(new Node(1, "host1", 1234, "rack-a"), 2, 5),
                  replicaInfo(new Node(2, "host2", 1234, "rack-b"), 3, 3),
                  replicaInfo(new Node(3, "host3", 1234, "rack-b"), 4, 2)
  
          ).collect(Collectors.toList());
      }
  
      static ReplicaView replicaInfo(Node node, long logOffset, long timeSinceLastCaughtUpMs) {
          return new ReplicaView.DefaultReplicaView(node, logOffset, timeSinceLastCaughtUpMs);
      }
  
      static PartitionView partitionInfo(Set<ReplicaView> replicaViewSet, ReplicaView leader) {
          return new PartitionView.DefaultPartitionView(replicaViewSet, leader);
      }
  
      static ClientMetadata metadata(String rack) {
          return new ClientMetadata.DefaultClientMetadata(rack, "test-client",
                  InetAddress.getLoopbackAddress(), KafkaPrincipal.ANONYMOUS, "TEST");
      }
  }
  