datebook

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

-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.Month`.\n").

-file("src/datebook/month.gleam", 23).
?DOC(
    " Returns the last day of the month in a given year.\n"
    "\n"
    " # Examples\n"
    "\n"
    " ```gleam\n"
    " last_day(March, 2005)\n"
    " // -> 31\n"
    " ```\n"
    "\n"
    " ```gleam\n"
    " last_day(February, 2024)\n"
    " // -> 29\n"
    " ```\n"
    " \n"
    " ```gleam\n"
    " last_day(February, 2025)\n"
    " // -> 28\n"
    " ```\n"
).
-spec last_day(gleam@time@calendar:month(), integer()) -> integer().
last_day(Month, Year) ->
    case Month of
        february ->
            case gleam@time@calendar:is_leap_year(Year) of
                true ->
                    29;

                false ->
                    28
            end;

        april ->
            30;

        june ->
            30;

        september ->
            30;

        november ->
            30;

        january ->
            31;

        march ->
            31;

        may ->
            31;

        july ->
            31;

        august ->
            31;

        october ->
            31;

        december ->
            31
    end.

-file("src/datebook/month.gleam", 50).
?DOC(
    " Returns the next month for a given `Month`.\n"
    "\n"
    " # Examples\n"
    "\n"
    " ```gleam\n"
    " next(March)\n"
    " // -> April\n"
    " ```\n"
).
-spec next(gleam@time@calendar:month()) -> gleam@time@calendar:month().
next(Month) ->
    case Month of
        january ->
            february;

        february ->
            march;

        march ->
            april;

        april ->
            may;

        may ->
            june;

        june ->
            july;

        july ->
            august;

        august ->
            september;

        september ->
            october;

        october ->
            november;

        november ->
            december;

        december ->
            january
    end.

-file("src/datebook/month.gleam", 75).
?DOC(
    " Returns the previous month for a given `Month`.\n"
    "\n"
    " # Examples\n"
    "\n"
    " ```gleam\n"
    " previous(March)\n"
    " // -> February\n"
    " ```\n"
).
-spec previous(gleam@time@calendar:month()) -> gleam@time@calendar:month().
previous(Month) ->
    case Month of
        january ->
            december;

        february ->
            january;

        march ->
            february;

        april ->
            march;

        may ->
            april;

        june ->
            may;

        july ->
            june;

        august ->
            july;

        september ->
            august;

        october ->
            september;

        november ->
            october;

        december ->
            november
    end.