-type flow() ::
          #flow{id :: binary(),
                module :: module(),
                module_vsn :: undefined | module_vsn(),
                stream_filter :: undefined | string(),
                stream_names :: undefined | stream_names(),
                mapper_window :: undefined | pos_integer(),
                mapper_nodes :: undefined | [node()],
                mapper_opts :: mapper_opts(),
                reducer_window :: undefined | pos_integer(),
                reducer_node :: node(),
                reducer_opts :: reducer_opts(),
                reducer_skip :: undefined | boolean(),
                output_opts :: output_opts(),
                heartbeat :: undefined | pos_integer(),
                window_sync :: undefined | boolean(),
                started_at :: undefined | erlang:timestamp(),
                start_node :: node()}.

-type flow_opts() ::
          {heartbeat, pos_integer()} |
          {mapper_opts, mapper_opts()} |
          {mapper_window, pos_integer()} |
          {output_opts, output_opts()} |
          {reducer_opts, reducer_opts()} |
          {reducer_skip, boolean()} |
          {reducer_window, pos_integer()} |
          {stream_filter, string()} |
          {stream_names, stream_names()} |
          {window_sync, boolean()}.

-type mapper_opts() :: term().

-type module_vsn() :: pos_integer().

-type output_opts() :: term().

-type reducer_opts() :: term().

-type stream_name() :: atom().

-type stream_names() :: [stream_name()].