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.raft.internals;
  
  import org.apache.kafka.raft.Batch;
  import org.apache.kafka.raft.BatchReader;
  
  import java.util.Collections;
  import java.util.Iterator;
  import java.util.List;
  import java.util.OptionalLong;
  
  public class MemoryBatchReader<T> implements BatchReader<T> {
      private final CloseListener<BatchReader<T>> closeListener;
      private final Iterator<Batch<T>> iterator;
      private final long baseOffset;
      private final long lastOffset;
  
      private MemoryBatchReader(
          long baseOffset,
          long lastOffset,
          Iterator<Batch<T>> iterator,
          CloseListener<BatchReader<T>> closeListener
      ) {
          this.baseOffset = baseOffset;
          this.lastOffset = lastOffset;
          this.iterator = iterator;
          this.closeListener = closeListener;
      }
  
      @Override
      public boolean hasNext() {
          return iterator.hasNext();
      }
  
      @Override
      public Batch<T> next() {
          return iterator.next();
      }
  
      @Override
      public long baseOffset() {
          return baseOffset;
      }
  
      @Override
      public OptionalLong lastOffset() {
          return OptionalLong.of(lastOffset);
      }
  
      @Override
      public void close() {
          closeListener.onClose(this);
      }
  
      public static <T> MemoryBatchReader<T> empty(
          long baseOffset,
          long lastOffset,
          CloseListener<BatchReader<T>> closeListener
      ) {
          return new MemoryBatchReader<>(
              baseOffset,
              lastOffset,
              Collections.emptyIterator(),
              closeListener
          );
      }
  
      public static <T> MemoryBatchReader<T> of(
          List<Batch<T>> batches,
          CloseListener<BatchReader<T>> closeListener
      ) {
          if (batches.isEmpty()) {
              throw new IllegalArgumentException("MemoryBatchReader requires at least " +
                  "one batch to iterate, but an empty list was provided");
          }
  
          return new MemoryBatchReader<>(
              batches.get(0).baseOffset(),
              batches.get(batches.size() - 1).lastOffset(),
              batches.iterator(),
              closeListener
          );
      }
  }
  