/**
 * The {@code GlobalCommitter} is responsible for creating and committing an aggregated committable,
 * which we call global committable (see {@link #combine}).
 *
 * <p>The {@code GlobalCommitter} runs with parallelism equal to 1.
 *
 * @param <CommT>         The type of information needed to commit data staged by the sink
 * @param <GlobalCommT>   The type of the aggregated committable
 */
public interface GlobalCommitter<CommT, GlobalCommT> extends AutoCloseable {

	/**
	 * Find out which global committables need to be retried when recovering from the failure.
	 * @param globalCommittables A list of {@link GlobalCommT} for which we want to verify
	 *                              which ones were successfully committed and which ones did not.
	 *
	 * @return A list of {@link GlobalCommT} that should be committed again.
	 *
	 * @throws IOException if fail to filter the recovered committables.
	 */
	List<GlobalCommT> filterRecoveredCommittables(List<GlobalCommT> globalCommittables) throws IOException;

	/**
	 * Compute an aggregated committable from a list of committables.
	 * @param committables A list of {@link CommT} to be combined into a {@link GlobalCommT}.
	 *
	 * @return an aggregated committable
	 *
	 * @throws IOException if fail to combine the given committables.
	 */
	GlobalCommT combine(List<CommT> committables) throws IOException;

	/**
	 * Commit the given list of {@link GlobalCommT}.
	 *
	 * @param globalCommittables a list of {@link GlobalCommT}.
	 *
	 * @return A list of {@link GlobalCommT} needed to re-commit, which is needed in case we implement a "commit-with-retry" pattern.
	 *
	 * @throws IOException if the commit operation fail and do not want to retry any more.
	 */
	List<GlobalCommT> commit(List<GlobalCommT> globalCommittables) throws IOException;

	/**
	 * Signals that there is no committable any more.
	 *
	 * @throws IOException if fail to handle this notification.
	 */
	void endOfInput() throws IOException;
}