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 org.apache.kafka.coordinator.group.modern;
  
  import org.apache.kafka.common.Uuid;
  import org.apache.kafka.coordinator.group.api.assignor.PartitionAssignor;
  import org.apache.kafka.coordinator.group.api.assignor.SubscribedTopicDescriber;
  import org.apache.kafka.image.MetadataImage;
  import org.apache.kafka.image.TopicImage;
  import org.apache.kafka.metadata.BrokerRegistration;
  import org.apache.kafka.metadata.PartitionRegistration;
  
  import java.util.Collections;
  import java.util.HashSet;
  import java.util.Objects;
  import java.util.Set;
  
  /**
   * The subscribed topic metadata class is used by the {@link PartitionAssignor} to obtain
   * topic and partition metadata for the topics that the modern group is subscribed to.
   */
  public class SubscribedTopicDescriberImpl implements SubscribedTopicDescriber {
      /**
       * The metadata image that contains the latest metadata information.
       */
      private final MetadataImage metadataImage;
  
      public SubscribedTopicDescriberImpl(MetadataImage metadataImage) {
          this.metadataImage = Objects.requireNonNull(metadataImage);
      }
  
      /**
       * The number of partitions for the given topic Id.
       *
       * @param topicId   Uuid corresponding to the topic.
       * @return The number of partitions corresponding to the given topic Id,
       *         or -1 if the topic Id does not exist.
       */
      @Override
      public int numPartitions(Uuid topicId) {
          TopicImage topicImage = this.metadataImage.topics().getTopic(topicId);
          return topicImage == null ? -1 : topicImage.partitions().size();
      }
  
      /**
       * Returns all the available racks associated with the replicas of the given partition.
       *
       * @param topicId       Uuid corresponding to the partition's topic.
       * @param partition     Partition Id within the topic.
       * @return The set of racks corresponding to the replicas of the topics partition.
       *         If the topic Id does not exist or no partition rack information is available, an empty set is returned.
       */
      @Override
      public Set<String> racksForPartition(Uuid topicId, int partition) {
          TopicImage topic = metadataImage.topics().getTopic(topicId);
          if (topic != null) {
              PartitionRegistration partitionRegistration = topic.partitions().get(partition);
              if (partitionRegistration != null) {
                  Set<String> racks = new HashSet<>();
                  for (int replica : partitionRegistration.replicas) {
                      // Only add the rack if it is available for the broker/replica.
                      BrokerRegistration brokerRegistration = metadataImage.cluster().broker(replica);
                      if (brokerRegistration != null) {
                          brokerRegistration.rack().ifPresent(racks::add);
                      }
                  }
                  return Collections.unmodifiableSet(racks);
              }
          }
          return Set.of();
      }
  
      @Override
      public boolean equals(Object o) {
          if (this == o) return true;
          if (o == null || getClass() != o.getClass()) return false;
          SubscribedTopicDescriberImpl that = (SubscribedTopicDescriberImpl) o;
          return metadataImage.equals(that.metadataImage);
      }
  
      @Override
      public int hashCode() {
          return Objects.hashCode(metadataImage);
      }
  
      @Override
      public String toString() {
          return "SubscribedTopicMetadata(" +
              "metadataImage=" + metadataImage +
              ')';
      }
  }
  