/**
 * Base interface for developing a sink. A basic {@link Sink} is a stateless sink that can flush
 * data on checkpoint to achieve at-least-once consistency. Sinks with additional requirements
 * should implement {@link StatefulSink} or {@link TwoPhaseCommittingSink}.
 *
 * <p>The {@link Sink} needs to be serializable. All configuration should be validated eagerly. The
 * respective sink writers are transient and will only be created in the subtasks on the
 * taskmanagers.
 *
 * @param <InputT> The type of the sink's input
 */
@PublicEvolving
public interface Sink<InputT> extends Serializable {

    /**
     * Create a {@link SinkWriter}.
     *
     * @param context the runtime context.
     * @return A sink writer.
     * @throws IOException for any failure during creation.
     */
    SinkWriter<InputT> createWriter(InitContext context) throws IOException;

    /** The interface exposes some runtime info for creating a {@link SinkWriter}. */
    interface InitContext {
  ... Similar to Sink V1 InitContext
    }
}

/**
 * A {@link Sink} with a stateful {@link SinkWriter}.
 *
 * <p>The {@link StatefulSink} needs to be serializable. All configuration should be validated
 * eagerly. The respective sink writers are transient and will only be created in the subtasks on
 * the taskmanagers.
 *
 * @param <InputT> The type of the sink's input
 * @param <WriterStateT> The type of the sink writer's state
 */
@PublicEvolving
public interface StatefulSink<InputT, WriterStateT> extends Sink<InputT> {

    /**
     * Create a {@link StatefulSinkWriter}.
     *
     * @param context the runtime context.
     * @return A sink writer.
     * @throws IOException for any failure during creation.
     */
    StatefulSinkWriter<InputT, WriterStateT> createWriter(InitContext context) throws IOException;

    /**
     * Create a {@link StatefulSinkWriter} from a recovered state.
     *
     * @param context the runtime context.
     * @return A sink writer.
     * @throws IOException for any failure during creation.
     */
    StatefulSinkWriter<InputT, WriterStateT> recoverWriter(
            InitContext context, Collection<WriterStateT> recoveredState) throws IOException;

    /**
     * Any stateful sink needs to provide this state serializer and implement {@link
     * StatefulSinkWriter#snapshotState(long)} properly. The respective state is used in {@link
     * #recoverWriter(InitContext, Collection)} on recovery.
     *
     * @return the serializer of the writer's state type.
     */
    SimpleVersionedSerializer<WriterStateT> getWriterStateSerializer();

    interface StateCompatible {
        /**
         * A list of state names of sinks from which the state can be restored. For example, the new
         * {@code FileSink} can resume from the state of an old {@code StreamingFileSink} as a
         * drop-in replacement when resuming from a checkpoint/savepoint.
         */
        Collection<String> getCompatibleWriterStateNames();
    }

    /**
     * A {@link SinkWriter} whose state needs to be checkpointed.
     *
     * @param <InputT> The type of the sink writer's input
     * @param <WriterStateT> The type of the writer's state
     */
    @PublicEvolving
    interface StatefulSinkWriter<InputT, WriterStateT> extends SinkWriter<InputT> {
        /**
         * @return The writer's state.
         * @throws IOException if fail to snapshot writer's state.
         */
        Collection<WriterStateT> snapshotState(long checkpointId) throws IOException;
    }
}

/**
 * A {@link Sink} for exactly-once semantics using a two-phase commit protocol. The {@link Sink}
 * consists of a {@link SinkWriter} that performs the precommits and a {@link Committer} that
 * actually commits the data. To facilitate the separation the {@link SinkWriter} creates
 * <i>committables</i> on checkpoint or end of input and the sends it to the {@link Committer}.
 *
 * <p>The {@link TwoPhaseCommittingSink} needs to be serializable. All configuration should be
 * validated eagerly. The respective sink writers and committers are transient and will only be
 * created in the subtasks on the taskmanagers.
 *
 * @param <InputT> The type of the sink's input
 * @param <CommT> The type of the committables.
 */
@PublicEvolving
public interface TwoPhaseCommittingSink<InputT, CommT> extends Sink<InputT> {

    /**
     * Create a {@link PrecommittingSinkWriter} that creates committables on checkpoint or end of
     * input.
     *
     * @param context the runtime context.
     * @return A sink writer for the two-phase commit protocol.
     * @throws IOException for any failure during creation.
     */
    PrecommittingSinkWriter<InputT, CommT> createWriter(InitContext context) throws IOException;

    /**
     * Creates a {@link Committer} that permanently makes the previously written data visible
     * through {@link Committer#commit(Collection)}.
     *
     * @return A committer for the two-phase commit protocol.
     * @throws IOException for any failure during creation.
     */
    Committer<CommT> createComm
itter() throws IOException;

    /** Returns the serializer of the committable type. */
    SimpleVersionedSerializer<CommT> getCommittableSerializer();


    /** A {@link SinkWriter} that performs the first part of a 2pc protocol. */
	@PublicEvolving
    interface PrecommittingSinkWriter<InputT, CommT> extends SinkWriter<InputT> {
        /**
         * Prepare for a commit.
         *
         * <p>This method will be called after {@link #flush(boolean)} and before {@link
         * StatefulSinkWriter#snapshotState(long)}.
         *
         * @return The data to commit as the second step of the 2pc protocol.
         * @throws IOException if fail to prepare for a commit.
         */
        Collection<CommT> prepareCommit() throws IOException, InterruptedException;
    }
}

/** Allows expert users to implement a custom topology before {@link SinkWriter}. */
@Experimental
public interface WithPreWriteTopology<InputT> extends Sink<InputT> {

    /**
     * Adds an arbitrary topology before the writer. The topology may be used to repartition the
     * data.
     *
     * @param inputDataStream the stream of input records.
     * @return the custom topology before {@link SinkWriter}.
     */
    DataStream<InputT> addPreWriteTopology(DataStream<InputT> inputDataStream);
}

/**
 * Allows expert users to implement a custom topology after {@link SinkWriter} and before {@link
 * Committer}.
 */
@Experimental
public interface WithPreCommitTopology<InputT, CommT>
        extends TwoPhaseCommittingSink<InputT, CommT> {

    /**
     * Intercepts and modifies the committables sent on checkpoint or at end of input. Implementers
     * need to ensure to modify all {@link CommittableMessage}s appropriately.
     *
     * @param committables the stream of committables.
     * @return the custom topology before {@link Committer}.
     */

    DataStream<CommittableMessage<CommT>> addPreCommitTopology(
            DataStream<CommittableMessage<CommT>> committables);
}

/** Allows expert users to implement a custom topology after {@link Committer}. */
@Experimental
public interface WithPostCommitTopology<InputT, CommT>
        extends TwoPhaseCommittingSink<InputT, CommT> {

    /**
     * Adds a custom post-commit topology where all committables can be processed.
     *
     * <p>It's strongly recommended to keep this pipeline stateless such that batch and streaming
     * modes do not require special cases.
     *
     * <p>All operations need to be idempotent: on recovery, any number of committables may be
     * replayed that have already been committed. It's mandatory that these committables have no
     * effect on the external system.
     */
    void addPostCommitTopology(DataStream<CommittableMessage<CommT>> committables);