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 com.datastax.oss.driver.internal.core;
  
  import com.datastax.oss.driver.api.core.AsyncPagingIterable;
  import com.datastax.oss.driver.api.core.MappedAsyncPagingIterable;
  import com.datastax.oss.driver.api.core.cql.ColumnDefinitions;
  import com.datastax.oss.driver.api.core.cql.ExecutionInfo;
  import com.datastax.oss.driver.shaded.guava.common.collect.AbstractIterator;
  import edu.umd.cs.findbugs.annotations.NonNull;
  import java.util.Iterator;
  import java.util.concurrent.CompletionStage;
  import java.util.function.Function;
  
  public class AsyncPagingIterableWrapper<SourceT, TargetT>
      implements MappedAsyncPagingIterable<TargetT> {
  
    private final AsyncPagingIterable<SourceT, ?> source;
    private final Function<? super SourceT, ? extends TargetT> elementMapper;
  
    private final Iterable<TargetT> currentPage;
  
    public AsyncPagingIterableWrapper(
        AsyncPagingIterable<SourceT, ?> source,
        Function<? super SourceT, ? extends TargetT> elementMapper) {
      this.source = source;
      this.elementMapper = elementMapper;
  
      Iterator<SourceT> sourceIterator = source.currentPage().iterator();
      Iterator<TargetT> iterator =
          new AbstractIterator<TargetT>() {
            @Override
            protected TargetT computeNext() {
              return sourceIterator.hasNext()
                  ? elementMapper.apply(sourceIterator.next())
                  : endOfData();
            }
          };
      this.currentPage = () -> iterator;
    }
  
    @NonNull
    @Override
    public ColumnDefinitions getColumnDefinitions() {
      return source.getColumnDefinitions();
    }
  
    @NonNull
    @Override
    public ExecutionInfo getExecutionInfo() {
      return source.getExecutionInfo();
    }
  
    @Override
    public int remaining() {
      return source.remaining();
    }
  
    @NonNull
    @Override
    public Iterable<TargetT> currentPage() {
      return currentPage;
    }
  
    @Override
    public boolean hasMorePages() {
      return source.hasMorePages();
    }
  
    @NonNull
    @Override
    public CompletionStage<MappedAsyncPagingIterable<TargetT>> fetchNextPage()
        throws IllegalStateException {
      return source
          .fetchNextPage()
          .thenApply(
              nextSource ->
                  new AsyncPagingIterableWrapper<SourceT, TargetT>(nextSource, elementMapper));
    }
  
    @Override
    public boolean wasApplied() {
      return source.wasApplied();
    }
  }
  