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.streams.processor.internals;
  
  import org.apache.kafka.common.TopicPartition;
  import org.apache.kafka.streams.processor.TaskId;
  
  import java.util.Map;
  import java.util.Set;
  
  /**
   * See {@link StoreChangelogReader}.
   */
  public interface ChangelogReader extends ChangelogRegister {
      /**
       * Restore all registered state stores by reading from their changelogs
       *
       * @return the total number of records restored in this call
       */
      long restore(final Map<TaskId, Task> tasks);
  
      /**
       * Transit to restore active changelogs mode
       */
      void enforceRestoreActive();
  
      /**
       * Transit to update standby changelogs mode
       */
      void transitToUpdateStandby();
  
      /**
       * @return true if the reader is in restoring active changelog mode;
       *         false if the reader is in updating standby changelog mode
       */
      boolean isRestoringActive();
  
      /**
       * @return the changelog partitions that have been completed restoring
       */
      Set<TopicPartition> completedChangelogs();
  
      /**
       * Returns whether all changelog partitions were completely read.
       *
       * Since changelog partitions for standby tasks are never completely read, this method will always return
       * {@code false} if the changelog reader registered changelog partitions for standby tasks.
       *
       * @return {@code true} if all changelog partitions were completely read and no standby changelog partitions are read,
       *         {@code false} otherwise
       */
      boolean allChangelogsCompleted();
  
      /**
       * Clear all partitions
       */
      void clear();
  
      /**
       * @return whether the changelog reader has just been cleared or is uninitialized
       */
      boolean isEmpty();
  }
  