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/**
 * This class represents a kind of partitioned data stream. For this stream, Each key group is a
 * partition, and the partition to which the data belongs is determined.
 */
public interface KeyedPartitionStream<K, T> {
    /**
     * Apply an operation to this {@link KeyedPartitionStream}.
     *
     * <p>This method is used to avoid shuffle after applying the process function. It is required
     * that for the same record, the new {@link KeySelector} must extract the same key as the
     * original {@link KeySelector} on this {@link KeyedPartitionStream}.
     *
     * @param processFunction to perform operation.
     * @param newKeySelector to select the key after process.
     * @return new {@link KeyedPartitionStream} with this operation.
     */
    <OUT> KeyedPartitionStream<K, OUT> process(
            OneInputStreamProcessFunction<T, OUT> processFunction,
            KeySelector<OUT, K> newKeySelector);

    /**
     * Apply an operation to this {@link KeyedPartitionStream};
     *
     * @param processFunction to perform operation.
     * @return new {@link NonKeyedPartitionStream} with this operation.
     */
    <OUT> NonKeyedPartitionStream<OUT> process(
            OneInputStreamProcessFunction<T, OUT> processFunction);

    /**
     * Apply a two output operation to this {@link KeyedPartitionStream}.
     *
     * <p>This method is used to avoid shuffle after applying the process function. It is required
     * that for the same record, these new two {@link KeySelector}s must extract the same key as the
     * original {@link KeySelector}s on this {@link KeyedPartitionStream}.
     *
     * @param processFunction to perform two output operation.
     * @param keySelector1 to select the key of first output.
     * @param keySelector2 to select the key of second output.
     * @return new {@link TwoKeyedPartitionStreamTwoKeyedPartitionStreams} with this operation.
     */
    <OUT1, OUT2> TwoKeyedPartitionStreams<K, OUT1, OUT2> process(
            TwoOutputStreamProcessFunction<T, OUT1, OUT2> processFunction,
            KeySelector<OUT1, K> keySelector1,
            KeySelector<OUT2, K> keySelector2);

    /**
     * Apply a two output operation to this {@link KeyedPartitionStream}.
     *
     * @param processFunction to perform two output operation.
     * @return new {@link TwoNonKeyedPartitionStreamTwoNonKeyedPartitionStreams} with this operation.
     */
    <OUT1, OUT2> TwoNonKeyedPartitionStreams<OUT1, OUT2> process(
            TwoOutputStreamProcessFunction<T, OUT1, OUT2> processFunction);

    /**
     * Apply a two input operation to this and other {@link KeyedPartitionStream}. The two keyed
     * streams must have the same partitions, otherwise it makes no sense to connect them.
     *
     * @param other {@link KeyedPartitionStream} to perform operation with two input.
     * @param processFunction to perform operation.
     * @return new {@link NonKeyedPartitionStream} with this operation.
     */
    <T_OTHER, OUT> NonKeyedPartitionStream<OUT> connectAndProcess(
            KeyedPartitionStream<K, T_OTHER> other,
            TwoInputNonBroadcastStreamProcessFunction<T, T_OTHER, OUT> processFunction);

     /**
     * Apply a two input operation to this and other {@link KeyedPartitionStream}.The two keyed
     * streams must have the same partitions, otherwise it makes no sense to connect them.
     *
     * <p>This method is used to avoid shuffle after applying the process function. It is required
     * that for the same record, the new {@link KeySelector} must extract the same key as the
     * original {@link KeySelector}s on these two {@link KeyedPartitionStream}s.
     *
     * @param other {@link KeyedPartitionStream} to perform operation with two input.
     * @param processFunction to perform operation.
     * @param newKeySelector to select the key after process.
     * @return new {@link KeyedPartitionStream} with this operation.
     */
    <T_OTHER, OUT> KeyedPartitionStream<K, OUT> connectAndProcess(
            KeyedPartitionStream<K, T_OTHER> other,
            TwoInputNonBroadcastStreamProcessFunction<T, T_OTHER, OUT> processFunction,
            KeySelector<OUT, K> newKeySelector);

    /**
     * Apply a two input operation to this and other {@link BroadcastStream}.
     *
     * @param processFunction to perform operation.
     * @return new stream with this operation.
     */
    <T_OTHER, OUT> NonKeyedPartitionStream<OUT> connectAndProcess(
            BroadcastStream<T_OTHER> other,
            TwoInputBroadcastStreamProcessFunction<T, T_OTHER, OUT> processFunction);

    /**
     * Apply a two input operation to this and other {@link BroadcastStream}.
     *
     * <p>This method is used to avoid shuffle after applying the process function. It is required
     * that for the record from non-broadcast input, the new {@link KeySelector} must extract the
     * same key as the original {@link KeySelector}s on the {@link KeyedPartitionStream}. For the
     * record from broadcast input, the output key from keyed partition itself instead of new key
     * selector, so it is safe already.
     *
     * @param other {@link BroadcastStream} to perform operation with two input.
     * @param processFunction to perform operation.
     * @param newKeySelector to select the key after process.
     * @return new {@link KeyedPartitionStream} with this operation.
     */
    <T_OTHER, OUT> KeyedPartitionStream<K, OUT> connectAndProcess(
            BroadcastStream<T_OTHER> other,
            TwoInputBroadcastStreamProcessFunction<T, T_OTHER, OUT> processFunction,
            KeySelector<OUT, K> newKeySelector);

    /**
     * Coalesce this stream to a {@link GlobalStream}.
     *
     * @return the coalesced global stream.
     */
    GlobalStream<T> global();

    /**
     * Transform this stream to a new {@link KeyedPartitionStream}.
     *
     * @param keySelector to decide how to map data to partition.
     * @return the transformed stream partitioned by key.
     */
    <NEW_KEY> KeyedPartitionStream<NEW_KEY, T> keyBy(KeySelector<T, NEW_KEY> keySelector);

    /**
     * Transform this stream to a new {@link NonKeyedPartitionStream}, data will be shuffled between
     * these two streams.
     *
     * @return the transformed stream after shuffle.
     */
    NonKeyedPartitionStream<T> shuffle();

    /**
     * Transform this stream to a new {@link BroadcastStream}.
     *
     * @return the transformed {@link BroadcastStream}.
     */
    BroadcastStream<T> broadcast();

    /**
     * Sink data from this stream.
     *
     * @param sink to receive data from this stream.
     */
    void toSink(Sink<T> sink);

    /**
     * This class represents a combination of two {@link KeyedPartitionStream}. It will be used as
     * the return value of operation with two output.
     */
    interface TwoKeyedPartitionStreams<K, T1, T2> {
        /** Get the first stream. */
        KeyedPartitionStream<K, T1> getFirst();

        /** Get the second stream. */
        KeyedPartitionStream<K, T2> getSecond();
    }
}