% Functor applicator. Functor returns turple passed with some elem

%   wrapped into fun-parameter.

%

on_fst(F) -> fun ({A, B}) -> { F(A), B } end.

on_snd(F) -> fun ({A, B}) -> { A, F(B) } end.



% Datetime-structure clearers.

%

zero_1() -> fun ({A, B, _}) -> { A, B, 0 } end.

zero_2() -> fun ({A, _, _}) -> { A, 0, 0 } end.

zero_3() -> fun ({_, _, _}) -> { 0, 0, 0 } end.



% Returns the functor, clamping datetime to candle start.

%

candle_open(Scale) ->

    case Scale of

        minute -> c([ on_fst(id()),        on_snd(zero_1()) ]);



        hour ->   c([ on_fst(id()),        on_snd(zero_2()) ]);



        day ->    c([ on_fst(id()),        on_snd(zero_3()) ]);



        month ->  c([ on_fst(zero_1()),    on_snd(zero_3()) ]);



        week ->   c([ on_fst(open_week()), on_snd(zero_3()) ])

    end.



% Returns the functor clamping date to week start.

%

open_week() ->

    fun (Date) ->

        Seconds = t({ Date, { 0, 0, 0} }),

        WeekStart = Seconds - (calendar:day_of_the_week(Date) - 1) * 24 * 60 * 60,

        { NewDate, _ } = un_t(WeekStart),

        NewDate

    end.



% Returns property selector from some datetime.

%

property(Scale) ->

    fun (Trade) ->

        {{Y, Mth, D}, {H, M, _S}} = Trade#trade.point,

        case Scale of

            minute -> M;

            hour   -> H;

            day    -> D;

            month  -> Mth;

            week   -> calendar:iso_week_number({Y, Mth, D})

        end

    end.



% Datetime to second (and back) converters.

%

t   (GregTime) -> calendar:datetime_to_gregorian_seconds(GregTime).

un_t(Datetime) -> calendar:gregorian_seconds_to_datetime(Datetime).