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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
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   *
   *    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.
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  package org.apache.kafka.clients;
  
  import org.apache.kafka.common.Cluster;
  import org.apache.kafka.common.Node;
  import org.apache.kafka.common.PartitionInfo;
  import org.apache.kafka.common.TopicPartition;
  import org.apache.kafka.common.Uuid;
  import org.apache.kafka.common.protocol.Errors;
  import org.apache.kafka.common.requests.MetadataResponse;
  
  import org.junit.jupiter.api.Test;
  
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.Optional;
  import java.util.OptionalInt;
  import java.util.function.Function;
  import java.util.stream.Collectors;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertNull;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  public class MetadataSnapshotTest {
  
      @Test
      public void testMissingLeaderEndpoint() {
          // Although the broker attempts to ensure leader information is available, the
          // client metadata cache may retain partition metadata across multiple responses.
          // For example, separate responses may contain conflicting leader epochs for
          // separate partitions and the client will always retain the highest.
  
          TopicPartition topicPartition = new TopicPartition("topic", 0);
  
          MetadataResponse.PartitionMetadata partitionMetadata = new MetadataResponse.PartitionMetadata(
                  Errors.NONE,
                  topicPartition,
                  Optional.of(5),
                  Optional.of(10),
                  Arrays.asList(5, 6, 7),
                  Arrays.asList(5, 6, 7),
                  Collections.emptyList());
  
          Map<Integer, Node> nodesById = new HashMap<>();
          nodesById.put(6, new Node(6, "localhost", 2077));
          nodesById.put(7, new Node(7, "localhost", 2078));
          nodesById.put(8, new Node(8, "localhost", 2079));
  
          MetadataSnapshot cache = new MetadataSnapshot("clusterId",
                  nodesById,
                  Collections.singleton(partitionMetadata),
                  Collections.emptySet(),
                  Collections.emptySet(),
                  Collections.emptySet(),
                  null,
                  Collections.emptyMap());
  
          Cluster cluster = cache.cluster();
          assertNull(cluster.leaderFor(topicPartition));
  
          PartitionInfo partitionInfo = cluster.partition(topicPartition);
          Map<Integer, Node> replicas = Arrays.stream(partitionInfo.replicas())
                  .collect(Collectors.toMap(Node::id, Function.identity()));
          assertNull(partitionInfo.leader());
          assertEquals(3, replicas.size());
          assertTrue(replicas.get(5).isEmpty());
          assertEquals(nodesById.get(6), replicas.get(6));
          assertEquals(nodesById.get(7), replicas.get(7));
      }
  
      @Test
      public void testMergeWithThatPreExistingPartitionIsRetainedPostMerge() {
          // Set up a Metadata Cache with 1 topic partition belong topic1.
          String topic1 = "topic1";
          TopicPartition topic1Partition = new TopicPartition(topic1, 1);
          MetadataResponse.PartitionMetadata partitionMetadata1 = new MetadataResponse.PartitionMetadata(
              Errors.NONE,
              topic1Partition,
              Optional.of(5),
              Optional.of(10),
              Arrays.asList(5, 6, 7),
              Arrays.asList(5, 6, 7),
              Collections.emptyList());
  
          Map<Integer, Node> nodesById = new HashMap<>();
          nodesById.put(6, new Node(6, "localhost", 2077));
          nodesById.put(7, new Node(7, "localhost", 2078));
          nodesById.put(8, new Node(8, "localhost", 2079));
  
          Map<String, Uuid> topicsIds = new HashMap<>();
          Uuid topic1Id = Uuid.randomUuid();
          topicsIds.put(topic1Partition.topic(), topic1Id);
  
          MetadataSnapshot cache = new MetadataSnapshot("clusterId",
              nodesById,
              Collections.singleton(partitionMetadata1),
              Collections.emptySet(),
              Collections.emptySet(),
              Collections.emptySet(),
              null,
              topicsIds);
  
          Cluster cluster = cache.cluster();
          assertEquals(1, cluster.topics().size());
          assertEquals(topic1Id, cluster.topicId(topic1));
          assertEquals(topic1, cluster.topicName(topic1Id));
  
          // Merge the metadata cache with a new partition topic2Partition.
          String topic2 = "topic2";
          TopicPartition topic2Partition = new TopicPartition(topic2, 2);
          MetadataResponse.PartitionMetadata partitionMetadata2 = new MetadataResponse.PartitionMetadata(
              Errors.NONE,
              topic2Partition,
              Optional.of(5),
              Optional.of(10),
              Arrays.asList(5, 6, 7),
              Arrays.asList(5, 6, 7),
              Collections.emptyList());
          topicsIds = new HashMap<>();
          Uuid topic2Id = Uuid.randomUuid();
          topicsIds.put(topic2Partition.topic(), topic2Id);
          cache = cache.mergeWith("clusterId", nodesById, Collections.singleton(partitionMetadata2),
              Collections.emptySet(), Collections.emptySet(), Collections.emptySet(), null, topicsIds, (topic, retain) -> true);
          cluster = cache.cluster();
  
          // Verify topic1Partition is retained & topic2Partition is added.
          assertEquals(2, cluster.topics().size());
  
          assertEquals(topic1Id, cluster.topicId(topic1));
          assertEquals(topic1, cluster.topicName(topic1Id));
  
          assertEquals(topic2Id, cluster.topicId(topic2));
          assertEquals(topic2, cluster.topicName(topic2Id));
      }
  
      @Test
      public void testTopicNamesCacheBuiltFromTopicIds() {
          Map<String, Uuid> topicIds = new HashMap<>();
          topicIds.put("topic1", Uuid.randomUuid());
          topicIds.put("topic2", Uuid.randomUuid());
  
          MetadataSnapshot cache = new MetadataSnapshot("clusterId",
                  Collections.singletonMap(6, new Node(6, "localhost", 2077)),
                  Collections.emptyList(),
                  Collections.emptySet(),
                  Collections.emptySet(),
                  Collections.emptySet(),
                  null,
                  topicIds);
  
          Map<Uuid, String> expectedNamesCache =
                  topicIds.entrySet().stream().collect(Collectors.toMap(Map.Entry::getValue,
                          Map.Entry::getKey));
          assertEquals(expectedNamesCache, cache.topicNames());
      }
  
      @Test
      public void testEmptyTopicNamesCacheBuiltFromTopicIds() {
          Map<String, Uuid> topicIds = new HashMap<>();
  
          MetadataSnapshot cache = new MetadataSnapshot("clusterId",
                  Collections.singletonMap(6, new Node(6, "localhost", 2077)),
                  Collections.emptyList(),
                  Collections.emptySet(),
                  Collections.emptySet(),
                  Collections.emptySet(),
                  null,
                  topicIds);
          assertEquals(Collections.emptyMap(), cache.topicNames());
      }
  
      @Test
      public void testLeaderEpochFor() {
          // Setup partition 0 with a leader-epoch of 10.
          TopicPartition topicPartition1 = new TopicPartition("topic", 0);
          MetadataResponse.PartitionMetadata partitionMetadata1 = new MetadataResponse.PartitionMetadata(
              Errors.NONE,
              topicPartition1,
              Optional.of(5),
              Optional.of(10),
              Arrays.asList(5, 6, 7),
              Arrays.asList(5, 6, 7),
              Collections.emptyList());
  
          // Setup partition 1 with an unknown leader epoch.
          TopicPartition topicPartition2 = new TopicPartition("topic", 1);
          MetadataResponse.PartitionMetadata partitionMetadata2 = new MetadataResponse.PartitionMetadata(
              Errors.NONE,
              topicPartition2,
              Optional.of(5),
              Optional.empty(),
              Arrays.asList(5, 6, 7),
              Arrays.asList(5, 6, 7),
              Collections.emptyList());
  
          Map<Integer, Node> nodesById = new HashMap<>();
          nodesById.put(5, new Node(5, "localhost", 2077));
          nodesById.put(6, new Node(6, "localhost", 2078));
          nodesById.put(7, new Node(7, "localhost", 2079));
  
          MetadataSnapshot cache = new MetadataSnapshot("clusterId",
              nodesById,
              Arrays.asList(partitionMetadata1, partitionMetadata2),
              Collections.emptySet(),
              Collections.emptySet(),
              Collections.emptySet(),
              null,
              Collections.emptyMap());
  
          assertEquals(OptionalInt.of(10), cache.leaderEpochFor(topicPartition1));
  
          assertEquals(OptionalInt.empty(), cache.leaderEpochFor(topicPartition2));
  
          assertEquals(OptionalInt.empty(), cache.leaderEpochFor(new TopicPartition("topic_missing", 0)));
      }
  
  }
  