datebook

-module(datebook@date).
-compile([no_auto_import, nowarn_unused_vars, nowarn_unused_function, nowarn_nomatch, inline]).
-define(FILEPATH, "src/datebook/date.gleam").
-export([next/1, previous/1, range/2]).

-if(?OTP_RELEASE >= 27).
-define(MODULEDOC(Str), -moduledoc(Str)).
-define(DOC(Str), -doc(Str)).
-else.
-define(MODULEDOC(Str), -compile([])).
-define(DOC(Str), -compile([])).
-endif.

?MODULEDOC(" Utility functions for `gleam/time`'s `calendar.Date`.\n").

-file("src/datebook/date.gleam", 16).
?DOC(
    " Returns the next `Date` for a given `Date`.\n"
    "\n"
    " # Examples\n"
    "\n"
    " ```gleam\n"
    " next(calendar.Date(2026, calendar.March, 22))\n"
    " // -> calendar.Date(2026, calendar.March, 23)\n"
    " ```\n"
).
-spec next(gleam@time@calendar:date()) -> gleam@time@calendar:date().
next(Date) ->
    {Month, Day} = case erlang:element(4, Date) =:= datebook@month:last_day(
        erlang:element(3, Date),
        erlang:element(2, Date)
    ) of
        true ->
            {datebook@month:next(erlang:element(3, Date)), 1};

        false ->
            {erlang:element(3, Date), erlang:element(4, Date) + 1}
    end,
    Year = case {Month, Day} of
        {january, 1} ->
            erlang:element(2, Date) + 1;

        {_, _} ->
            erlang:element(2, Date)
    end,
    {date, Year, Month, Day}.

-file("src/datebook/date.gleam", 38).
?DOC(
    " Returns the previous `Date` for a given `Date`.\n"
    "\n"
    " # Examples\n"
    "\n"
    " ```gleam\n"
    " previous(calendar.Date(2026, calendar.March, 22))\n"
    " // -> calendar.Date(2026, calendar.March, 21)\n"
    " ```\n"
).
-spec previous(gleam@time@calendar:date()) -> gleam@time@calendar:date().
previous(Date) ->
    {Month@1, Day} = case erlang:element(4, Date) =:= 1 of
        true ->
            Month = datebook@month:previous(erlang:element(3, Date)),
            {Month, datebook@month:last_day(Month, erlang:element(2, Date))};

        false ->
            {erlang:element(3, Date), erlang:element(4, Date) - 1}
    end,
    Year = case {Month@1, Day} of
        {december, 31} ->
            erlang:element(2, Date) - 1;

        {_, _} ->
            erlang:element(2, Date)
    end,
    {date, Year, Month@1, Day}.

-file("src/datebook/date.gleam", 55).
-spec range_rec(
    gleam@time@calendar:date(),
    gleam@time@calendar:date(),
    list(gleam@time@calendar:date())
) -> list(gleam@time@calendar:date()).
range_rec(From, To, Acc) ->
    case From =:= To of
        true ->
            [From | Acc];

        false ->
            range_rec(From, previous(To), [To | Acc])
    end.

-file("src/datebook/date.gleam", 88).
?DOC(
    " Returns the inclusive list of dates between `from` and `to`.\n"
    " \n"
    " Fails if `from` > `to`.\n"
    "\n"
    " # Examples\n"
    "\n"
    " ```gleam\n"
    " range(Date(2026, March, 29), Date(2026, April, 2))\n"
    " // -> Ok([\n"
    " //   Date(2026, March, 29),\n"
    " //   Date(2026, March, 30),\n"
    " //   Date(2026, March, 31),\n"
    " //   Date(2026, April, 1),\n"
    " //   Date(2026, April, 2),\n"
    " // ])\n"
    " ```\n"
    "\n"
    " ```gleam\n"
    " range(Date(2026, March, 22), Date(2026, March, 22))\n"
    " // -> Ok([Date(2026, March, 22)])\n"
    " ```\n"
    "\n"
    " ```gleam\n"
    " range(Date(2026, March, 22), Date(2026, March, 21))\n"
    " // -> Error(Nil)\n"
    " ```\n"
).
-spec range(gleam@time@calendar:date(), gleam@time@calendar:date()) -> {ok,
        list(gleam@time@calendar:date())} |
    {error, nil}.
range(From, To) ->
    gleam@bool:guard(
        gleam@time@calendar:naive_date_compare(From, To) =:= gt,
        {error, nil},
        fun() -> {ok, range_rec(From, To, [])} end
    ).