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.streams.topics;
  
  import org.apache.kafka.common.errors.StreamsInvalidTopologyException;
  import org.apache.kafka.common.utils.LogContext;
  import org.apache.kafka.coordinator.group.generated.StreamsGroupTopologyValue.Subtopology;
  import org.apache.kafka.coordinator.group.generated.StreamsGroupTopologyValue.TopicInfo;
  
  import org.slf4j.Logger;
  
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.Map;
  import java.util.OptionalInt;
  import java.util.function.Function;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  
  /**
   * This class is responsible for setting up the changelog topics for a topology. For a given topology, which does not have the number
   * of partitions specified for changelog partitions, this class will determine the number of partitions for each non-source changelog topic.
   */
  public class ChangelogTopics {
  
      private final Logger log;
      private final Collection<Subtopology> subtopologies;
      private final Function<String, OptionalInt> topicPartitionCountProvider;
  
      /**
       * Constructor for ChangelogTopics.
       *
       * @param logContext                    The context for emitting log messages.
       * @param subtopologies                 The subtopologies for the requested topology.
       * @param topicPartitionCountProvider   Returns the number of partitions for a given topic, representing the current state of the broker
       *                                      as well as any partition number decisions that have already been made. In particular, we expect
       *                                      the number of partitions for all repartition topics defined, even if they do not exist in the
       *                                      broker yet.
       */
      public ChangelogTopics(
          final LogContext logContext,
          final Collection<Subtopology> subtopologies,
          final Function<String, OptionalInt> topicPartitionCountProvider
      ) {
          this.log = logContext.logger(getClass());
          this.subtopologies = subtopologies;
          this.topicPartitionCountProvider = topicPartitionCountProvider;
      }
  
      /**
       * Determines the number of partitions for each changelog topic in the requested topology.
       *
       * @throws IllegalStateException If a source topic does not have a partition count defined through topicPartitionCountProvider.
       *
       * @return the map of all changelog topics for the requested topology to their required number of partitions.
       */
      public Map<String, Integer> setup() {
          final Map<String, Integer> changelogTopicPartitions = new HashMap<>();
          for (Subtopology subtopology : subtopologies) {
              final OptionalInt maxNumPartitions =
                  Stream.concat(
                      subtopology.sourceTopics().stream(),
                      subtopology.repartitionSourceTopics().stream().map(TopicInfo::name)
                  ).mapToInt(this::getPartitionCountOrFail).max();
  
              if (maxNumPartitions.isEmpty()) {
                  throw new StreamsInvalidTopologyException("No source topics found for subtopology " + subtopology.subtopologyId());
              }
              for (final TopicInfo topicInfo : subtopology.stateChangelogTopics()) {
                  changelogTopicPartitions.put(topicInfo.name(), maxNumPartitions.getAsInt());
              }
          }
  
          if (!changelogTopicPartitions.isEmpty()) {
              log.debug("Expecting state changelog topic partitions {} for the requested topology.",
                  changelogTopicPartitions.entrySet().stream().map(e -> e.getKey() + ":" + e.getValue()).collect(Collectors.joining(", ")));
          }
  
          return changelogTopicPartitions;
      }
  
      private int getPartitionCountOrFail(String topic) {
          final OptionalInt topicPartitionCount = topicPartitionCountProvider.apply(topic);
          if (topicPartitionCount.isEmpty()) {
              throw new IllegalStateException("No partition count for source topic " + topic);
          }
          return topicPartitionCount.getAsInt();
      }
  }