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.beam.runners.dataflow.worker.windmill.state;
  
  import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
  import javax.annotation.Nonnull;
  import javax.annotation.Nullable;
  import org.apache.beam.sdk.coders.Coder;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Function;
  
  /** Function to extract an {@link Iterable} from the continuation-supporting page read future. */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class ToIterableFunction<ContinuationT, ResultT>
      implements Function<ValuesAndContPosition<ResultT, ContinuationT>, Iterable<ResultT>> {
    private final StateTag<ContinuationT> stateTag;
    private final Coder<?> coder;
    /**
     * Reader to request continuation pages from, or {@literal null} if no continuation pages
     * required.
     */
    private @Nullable WindmillStateReader reader;
  
    public ToIterableFunction(
        WindmillStateReader reader, StateTag<ContinuationT> stateTag, Coder<?> coder) {
      this.reader = reader;
      this.stateTag = stateTag;
      this.coder = coder;
    }
  
    @SuppressFBWarnings(
        value = "NP_METHOD_PARAMETER_TIGHTENS_ANNOTATION",
        justification = "https://github.com/google/guava/issues/920")
    @Override
    public Iterable<ResultT> apply(
        @Nonnull ValuesAndContPosition<ResultT, ContinuationT> valuesAndContPosition) {
      if (valuesAndContPosition.getContinuationPosition() == null) {
        // Number of values is small enough Windmill sent us the entire bag in one response.
        reader = null;
        return valuesAndContPosition.getValues();
      } else {
        // Return an iterable which knows how to come back for more.
        StateTag.Builder<ContinuationT> continuationTBuilder =
            StateTag.of(
                    stateTag.getKind(),
                    stateTag.getTag(),
                    stateTag.getStateFamily(),
                    valuesAndContPosition.getContinuationPosition())
                .toBuilder();
        if (stateTag.getSortedListRange() != null) {
          continuationTBuilder.setSortedListRange(stateTag.getSortedListRange());
        }
        if (stateTag.getMultimapKey() != null) {
          continuationTBuilder.setMultimapKey(stateTag.getMultimapKey());
        }
        if (stateTag.getOmitValues() != null) {
          continuationTBuilder.setOmitValues(stateTag.getOmitValues());
        }
        return new PagingIterable<>(
            reader, valuesAndContPosition.getValues(), continuationTBuilder.build(), coder);
      }
    }
  }
  