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.common.requests;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import java.util.Objects;
  
  public class FetchMetadata {
      public static final Logger log = LoggerFactory.getLogger(FetchMetadata.class);
  
      /**
       * The session ID used by clients with no session.
       */
      public static final int INVALID_SESSION_ID = 0;
  
      /**
       * The first epoch.  When used in a fetch request, indicates that the client
       * wants to create or recreate a session.
       */
      public static final int INITIAL_EPOCH = 0;
  
      /**
       * An invalid epoch.  When used in a fetch request, indicates that the client
       * wants to close any existing session, and not create a new one.
       */
      public static final int FINAL_EPOCH = -1;
  
      /**
       * The FetchMetadata that is used when initializing a new FetchSessionHandler.
       */
      public static final FetchMetadata INITIAL = new FetchMetadata(INVALID_SESSION_ID, INITIAL_EPOCH);
  
      /**
       * The FetchMetadata that is implicitly used for handling older FetchRequests that
       * don't include fetch metadata.
       */
      public static final FetchMetadata LEGACY = new FetchMetadata(INVALID_SESSION_ID, FINAL_EPOCH);
  
      /**
       * Returns the next epoch.
       *
       * @param prevEpoch The previous epoch.
       * @return          The next epoch.
       */
      public static int nextEpoch(int prevEpoch) {
          if (prevEpoch < 0) {
              // The next epoch after FINAL_EPOCH is always FINAL_EPOCH itself.
              return FINAL_EPOCH;
          } else if (prevEpoch == Integer.MAX_VALUE) {
              return 1;
          } else {
              return prevEpoch + 1;
          }
      }
  
      /**
       * The fetch session ID.
       */
      private final int sessionId;
  
      /**
       * The fetch session epoch.
       */
      private final int epoch;
  
      public FetchMetadata(int sessionId, int epoch) {
          this.sessionId = sessionId;
          this.epoch = epoch;
      }
  
      /**
       * Returns true if this is a full fetch request.
       */
      public boolean isFull() {
          return (this.epoch == INITIAL_EPOCH) || (this.epoch == FINAL_EPOCH);
      }
  
      public int sessionId() {
          return sessionId;
      }
  
      public int epoch() {
          return epoch;
      }
  
      @Override
      public int hashCode() {
          return Objects.hash(sessionId, epoch);
      }
  
      @Override
      public boolean equals(Object o) {
          if (this == o) return true;
          if (o == null || getClass() != o.getClass()) return false;
          FetchMetadata that = (FetchMetadata) o;
          return sessionId == that.sessionId && epoch == that.epoch;
      }
  
      /**
       * Return the metadata for the next request. The metadata is set to indicate that the client wants to close the
       * existing session.
       */
      public FetchMetadata nextCloseExisting() {
          return new FetchMetadata(sessionId, FINAL_EPOCH);
      }
  
      /**
       * Return the metadata for the next request. The metadata is set to indicate that the client wants to close the
       * existing session and create a new one if possible.
       */
      public FetchMetadata nextCloseExistingAttemptNew() {
          return new FetchMetadata(sessionId, INITIAL_EPOCH);
      }
  
      /**
       * Return the metadata for the next full fetch request.
       */
      public static FetchMetadata newIncremental(int sessionId) {
          return new FetchMetadata(sessionId, nextEpoch(INITIAL_EPOCH));
      }
  
      /**
       * Return the metadata for the next incremental response.
       */
      public FetchMetadata nextIncremental() {
          return new FetchMetadata(sessionId, nextEpoch(epoch));
      }
  
      @Override
      public String toString() {
          StringBuilder bld = new StringBuilder();
          if (sessionId == INVALID_SESSION_ID) {
              bld.append("(sessionId=INVALID, ");
          } else {
              bld.append("(sessionId=").append(sessionId).append(", ");
          }
          if (epoch == INITIAL_EPOCH) {
              bld.append("epoch=INITIAL)");
          } else if (epoch == FINAL_EPOCH) {
              bld.append("epoch=FINAL)");
          } else {
              bld.append("epoch=").append(epoch).append(")");
          }
          return bld.toString();
      }
  }
  