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.camel.component.kafka.consumer.support.classic;
  
  import java.util.Set;
  
  import org.apache.camel.spi.StateRepository;
  import org.apache.kafka.clients.consumer.Consumer;
  import org.apache.kafka.common.TopicPartition;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  /**
   * A resume strategy that uses Kafka's offset for resuming
   */
  public class OffsetPartitionAssignmentAdapter implements PartitionAssignmentAdapter {
  
      private static final Logger LOG = LoggerFactory.getLogger(OffsetPartitionAssignmentAdapter.class);
  
      private final StateRepository<String, String> offsetRepository;
      private Consumer<?, ?> consumer;
  
      public OffsetPartitionAssignmentAdapter(StateRepository<String, String> offsetRepository) {
          this.offsetRepository = offsetRepository;
      }
  
      @Override
      public void setConsumer(Consumer<?, ?> consumer) {
          this.consumer = consumer;
      }
  
      private void resumeFromOffset(final Consumer<?, ?> consumer, TopicPartition topicPartition, String offsetState) {
          // The state contains the last read offset, so you need to seek from the next one
          long offset = deserializeOffsetValue(offsetState) + 1;
          LOG.debug("Resuming partition {} from offset {} from state", topicPartition.partition(), offset);
          consumer.seek(topicPartition, offset);
      }
  
      public void handlePartitionAssignment() {
          Set<TopicPartition> assignments = consumer.assignment();
          for (TopicPartition topicPartition : assignments) {
              String offsetState = offsetRepository.getState(serializeOffsetKey(topicPartition));
              if (offsetState != null && !offsetState.isEmpty()) {
                  resumeFromOffset(consumer, topicPartition, offsetState);
              }
          }
      }
  
      public static String serializeOffsetKey(TopicPartition topicPartition) {
          return topicPartition.topic() + '/' + topicPartition.partition();
      }
  
      public static long deserializeOffsetValue(String offset) {
          return Long.parseLong(offset);
      }
  }
  