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.io.source;
  
  import java.io.Serializable;
  import java.util.List;
  import java.util.Map;
  import java.util.function.Function;
  import org.apache.beam.runners.core.construction.SerializablePipelineOptions;
  import org.apache.beam.runners.flink.FlinkPipelineOptions;
  import org.apache.beam.runners.flink.translation.utils.SerdeUtils;
  import org.apache.beam.runners.flink.translation.wrappers.streaming.io.source.bounded.FlinkBoundedSource;
  import org.apache.beam.runners.flink.translation.wrappers.streaming.io.source.impulse.BeamImpulseSource;
  import org.apache.beam.runners.flink.translation.wrappers.streaming.io.source.unbounded.FlinkUnboundedSource;
  import org.apache.beam.sdk.io.BoundedSource;
  import org.apache.beam.sdk.io.UnboundedSource;
  import org.apache.flink.api.common.eventtime.Watermark;
  import org.apache.flink.api.connector.source.Boundedness;
  import org.apache.flink.api.connector.source.Source;
  import org.apache.flink.api.connector.source.SplitEnumerator;
  import org.apache.flink.api.connector.source.SplitEnumeratorContext;
  import org.apache.flink.core.io.SimpleVersionedSerializer;
  
  /**
   * The base class for {@link FlinkBoundedSource} and {@link FlinkUnboundedSource}.
   *
   * @param <T> The data type of the records emitted by the raw Beam sources.
   * @param <OutputT> The data type of the records emitted by the Flink Source.
   */
  public abstract class FlinkSource<T, OutputT>
      implements Source<OutputT, FlinkSourceSplit<T>, Map<Integer, List<FlinkSourceSplit<T>>>> {
  
    protected final String stepName;
    protected final org.apache.beam.sdk.io.Source<T> beamSource;
    protected final Boundedness boundedness;
    protected final SerializablePipelineOptions serializablePipelineOptions;
  
    private final int numSplits;
  
    // ----------------- public static methods to construct sources --------------------
  
    public static <T> FlinkBoundedSource<T> bounded(
        String stepName,
        BoundedSource<T> boundedSource,
        SerializablePipelineOptions serializablePipelineOptions,
        int numSplits) {
      return new FlinkBoundedSource<>(
          stepName, boundedSource, serializablePipelineOptions, Boundedness.BOUNDED, numSplits);
    }
  
    public static <T> FlinkUnboundedSource<T> unbounded(
        String stepName,
        UnboundedSource<T, ?> source,
        SerializablePipelineOptions serializablePipelineOptions,
        int numSplits) {
      return new FlinkUnboundedSource<>(stepName, source, serializablePipelineOptions, numSplits);
    }
  
    public static FlinkBoundedSource<byte[]> boundedImpulse() {
      return new FlinkBoundedSource<>(
          "Impulse",
          new BeamImpulseSource(),
          new SerializablePipelineOptions(FlinkPipelineOptions.defaults()),
          Boundedness.BOUNDED,
          1,
          record -> Watermark.MAX_WATERMARK.getTimestamp());
    }
  
    // ------ Common implementations for both bounded and unbounded source ---------
  
    protected FlinkSource(
        String stepName,
        org.apache.beam.sdk.io.Source<T> beamSource,
        SerializablePipelineOptions serializablePipelineOptions,
        Boundedness boundedness,
        int numSplits) {
      this.stepName = stepName;
      this.beamSource = beamSource;
      this.serializablePipelineOptions = serializablePipelineOptions;
      this.boundedness = boundedness;
      this.numSplits = numSplits;
    }
  
    @Override
    public Boundedness getBoundedness() {
      return boundedness;
    }
  
    @Override
    public SplitEnumerator<FlinkSourceSplit<T>, Map<Integer, List<FlinkSourceSplit<T>>>>
        createEnumerator(SplitEnumeratorContext<FlinkSourceSplit<T>> enumContext) throws Exception {
      return createEnumerator(enumContext, false);
    }
  
    public SplitEnumerator<FlinkSourceSplit<T>, Map<Integer, List<FlinkSourceSplit<T>>>>
        createEnumerator(
            SplitEnumeratorContext<FlinkSourceSplit<T>> enumContext, boolean splitInitialized)
            throws Exception {
  
      if (boundedness == Boundedness.BOUNDED) {
        return new LazyFlinkSourceSplitEnumerator<>(
            enumContext, beamSource, serializablePipelineOptions.get(), numSplits, splitInitialized);
      } else {
        return new FlinkSourceSplitEnumerator<>(
            enumContext, beamSource, serializablePipelineOptions.get(), numSplits, splitInitialized);
      }
    }
  
    @Override
    public SplitEnumerator<FlinkSourceSplit<T>, Map<Integer, List<FlinkSourceSplit<T>>>>
        restoreEnumerator(
            SplitEnumeratorContext<FlinkSourceSplit<T>> enumContext,
            Map<Integer, List<FlinkSourceSplit<T>>> checkpoint)
            throws Exception {
      SplitEnumerator<FlinkSourceSplit<T>, Map<Integer, List<FlinkSourceSplit<T>>>> enumerator =
          createEnumerator(enumContext, true);
      checkpoint.forEach(
          (subtaskId, splitsForSubtask) -> enumerator.addSplitsBack(splitsForSubtask, subtaskId));
      return enumerator;
    }
  
    @Override
    public SimpleVersionedSerializer<FlinkSourceSplit<T>> getSplitSerializer() {
      return FlinkSourceSplit.serializer();
    }
  
    @Override
    public SimpleVersionedSerializer<Map<Integer, List<FlinkSourceSplit<T>>>>
        getEnumeratorCheckpointSerializer() {
      return SerdeUtils.getNaiveObjectSerializer();
    }
  
    public int getNumSplits() {
      return numSplits;
    }
  
    @FunctionalInterface
    public interface TimestampExtractor<T> extends Function<T, Long>, Serializable {}
  }
  