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.clients.consumer;
  
  import org.apache.kafka.common.requests.OffsetFetchResponse;
  
  import java.io.Serializable;
  import java.util.Objects;
  import java.util.Optional;
  
  /**
   * The Kafka offset commit API allows users to provide additional metadata (in the form of a string)
   * when an offset is committed. This can be useful (for example) to store information about which
   * node made the commit, what time the commit was made, etc.
   */
  public class OffsetAndMetadata implements Serializable {
      private static final long serialVersionUID = 2019555404968089681L;
  
      private final long offset;
      private final String metadata;
  
      // We use null to represent the absence of a leader epoch to simplify serialization.
      // I.e., older serializations of this class which do not have this field will automatically
      // initialize its value to null.
      private final Integer leaderEpoch;
  
      /**
       * Construct a new OffsetAndMetadata object for committing through {@link KafkaConsumer}.
       *
       * @param offset The offset to be committed
       * @param leaderEpoch Optional leader epoch of the last consumed record
       * @param metadata Non-null metadata
       */
      public OffsetAndMetadata(long offset, Optional<Integer> leaderEpoch, String metadata) {
          if (offset < 0)
              throw new IllegalArgumentException("Invalid negative offset");
  
          this.offset = offset;
          this.leaderEpoch = leaderEpoch.orElse(null);
  
          // The server converts null metadata to an empty string. So we store it as an empty string as well on the client
          // to be consistent.
          if (metadata == null)
              this.metadata = OffsetFetchResponse.NO_METADATA;
          else
              this.metadata = metadata;
      }
  
      /**
       * Construct a new OffsetAndMetadata object for committing through {@link KafkaConsumer}.
       * @param offset The offset to be committed
       * @param metadata Non-null metadata
       */
      public OffsetAndMetadata(long offset, String metadata) {
          this(offset, Optional.empty(), metadata);
      }
  
      /**
       * Construct a new OffsetAndMetadata object for committing through {@link KafkaConsumer}. The metadata
       * associated with the commit will be empty.
       * @param offset The offset to be committed
       */
      public OffsetAndMetadata(long offset) {
          this(offset, "");
      }
  
      public long offset() {
          return offset;
      }
  
      public String metadata() {
          return metadata;
      }
  
      /**
       * Get the leader epoch of the previously consumed record (if one is known). Log truncation is detected
       * if there exists a leader epoch which is larger than this epoch and begins at an offset earlier than
       * the committed offset.
       *
       * @return the leader epoch or empty if not known
       */
      public Optional<Integer> leaderEpoch() {
          if (leaderEpoch == null || leaderEpoch < 0)
              return Optional.empty();
          return Optional.of(leaderEpoch);
      }
  
      @Override
      public boolean equals(Object o) {
          if (this == o) return true;
          if (o == null || getClass() != o.getClass()) return false;
          OffsetAndMetadata that = (OffsetAndMetadata) o;
          return offset == that.offset &&
                  Objects.equals(metadata, that.metadata) &&
                  Objects.equals(leaderEpoch, that.leaderEpoch);
      }
  
      @Override
      public int hashCode() {
          return Objects.hash(offset, metadata, leaderEpoch);
      }
  
      @Override
      public String toString() {
          return "OffsetAndMetadata{" +
                  "offset=" + offset +
                  ", leaderEpoch=" + leaderEpoch +
                  ", metadata='" + metadata + '\'' +
                  '}';
      }
  
  }
  