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.flink.translation.wrappers.streaming.stableinput;
  
  import java.util.List;
  import java.util.stream.Collectors;
  import java.util.stream.Stream;
  import java.util.stream.StreamSupport;
  import org.apache.flink.api.common.state.ListState;
  import org.apache.flink.api.common.state.ListStateDescriptor;
  import org.apache.flink.runtime.state.KeyedStateBackend;
  import org.apache.flink.runtime.state.VoidNamespace;
  import org.apache.flink.runtime.state.VoidNamespaceSerializer;
  
  /** A keyed implementation of a {@link BufferingElementsHandler}. */
  @SuppressWarnings({
    "rawtypes" // TODO(https://github.com/apache/beam/issues/20447)
  })
  public class KeyedBufferingElementsHandler implements BufferingElementsHandler {
  
    static KeyedBufferingElementsHandler create(
        KeyedStateBackend backend, ListStateDescriptor<BufferedElement> stateDescriptor)
        throws Exception {
      return new KeyedBufferingElementsHandler(backend, stateDescriptor);
    }
  
    private final KeyedStateBackend<Object> backend;
    private final String stateName;
    private final ListState<BufferedElement> state;
  
    private KeyedBufferingElementsHandler(
        KeyedStateBackend<Object> backend, ListStateDescriptor<BufferedElement> stateDescriptor)
        throws Exception {
      this.backend = backend;
      this.stateName = stateDescriptor.getName();
      // Eagerly retrieve the state to work around https://jira.apache.org/jira/browse/FLINK-12653
      this.state =
          backend.getPartitionedState(
              VoidNamespace.INSTANCE, VoidNamespaceSerializer.INSTANCE, stateDescriptor);
    }
  
    @Override
    public void buffer(BufferedElement element) {
      try {
        // assumes state backend is already keyed
        state.add(element);
      } catch (Exception e) {
        throw new RuntimeException("Failed to buffer element in state backend." + element, e);
      }
    }
  
    @Override
    public Stream<BufferedElement> getElements() {
      return backend
          .getKeys(stateName, VoidNamespace.INSTANCE)
          .flatMap(
              key -> {
                try {
                  backend.setCurrentKey(key);
                  return StreamSupport.stream(state.get().spliterator(), false);
                } catch (Exception e) {
                  throw new RuntimeException(
                      "Failed to retrieve buffered element from state backend.", e);
                }
              });
    }
  
    @Override
    public void clear() {
      List keys = backend.getKeys(stateName, VoidNamespace.INSTANCE).collect(Collectors.toList());
      try {
        for (Object key : keys) {
          backend.setCurrentKey(key);
          state.clear();
        }
      } catch (Exception e) {
        throw new RuntimeException("Failed to clear buffered element state", e);
      }
    }
  }
  