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package io.ray.streaming.api.stream;

import io.ray.streaming.api.function.impl.AggregateFunction;
import io.ray.streaming.api.function.impl.ReduceFunction;
import io.ray.streaming.api.partition.Partition;
import io.ray.streaming.api.partition.impl.KeyPartition;
import io.ray.streaming.operator.StreamOperator;
import io.ray.streaming.operator.impl.ReduceOperator;
import io.ray.streaming.python.stream.PythonDataStream;
import io.ray.streaming.python.stream.PythonKeyDataStream;

/**
 * Represents a DataStream returned by a key-by operation.
 *
 * @param  Type of the key.
 * @param  Type of the data.
 */
@SuppressWarnings("unchecked")
public class KeyDataStream extends DataStream {

  public KeyDataStream(DataStream input, StreamOperator streamOperator) {
    super(input, streamOperator, (Partition) new KeyPartition());
  }

  /**
   * Create a java stream that reference passed python stream. Changes in new stream will be
   * reflected in referenced stream and vice versa
   */
  public KeyDataStream(PythonDataStream referencedStream) {
    super(referencedStream);
  }

  /**
   * Apply a reduce function to this stream.
   *
   * @param reduceFunction The reduce function.
   * @return A new DataStream.
   */
  public DataStream reduce(ReduceFunction reduceFunction) {
    return new DataStream<>(this, new ReduceOperator(reduceFunction));
  }

  /**
   * Apply an aggregate Function to this stream.
   *
   * @param aggregateFunction The aggregate function
   * @param  The type of aggregated intermediate data.
   * @param  The type of result data.
   * @return A new DataStream.
   */
  public  DataStream aggregate(AggregateFunction aggregateFunction) {
    return new DataStream<>(this, null);
  }

  /**
   * Convert this stream as a python stream. The converted stream and this stream are the same
   * logical stream, which has same stream id. Changes in converted stream will be reflected in this
   * stream and vice versa.
   */
  public PythonKeyDataStream asPythonStream() {
    return new PythonKeyDataStream(this);
  }

}