defmodule TimeUtil do
    @moduledoc false

    def cur_year() do
        {{year, _, _}, _} = :calendar.local_time
        year
    end

    def cur_ymd() do
        {ymd, _} = :calendar.local_time
        ymd
    end

    @day_30 [2, 4, 6, 9, 11]
    @hms {0, 0, 0}
    def ym_first_last_day() do
        {{y, m, d}, _} = :calendar.local_time
        t = cond do
            m == 2 ->
                case rem(y, 4) == 0 && rem(y, 100) != 0 do
                    true ->
                        {y, m, 29}
                    _ ->
                        {y, m, 28}
                end
            Enum.member?(@day_30, m) ->
                {y, m, 30}
            true ->
                {y, m, 31}
        end
        {NaiveDateTime.from_erl!({{y, m, 1}, @hms}), NaiveDateTime.from_erl!({t, @hms})}
    end


    def naive_local_now,
        do: :calendar.local_time
            |> NaiveDateTime.from_erl!

    def naive_local_now_string,
        do: :calendar.local_time
            |> NaiveDateTime.from_erl!
            |> NaiveDateTime.to_string

    def naive_date_today,
        do: :calendar.local_time
            |> NaiveDateTime.from_erl!
            |> NaiveDateTime.to_date

    def naive_date_today_string,
        do: :calendar.local_time
            |> NaiveDateTime.from_erl!
            |> NaiveDateTime.to_date
            |> Date.to_string

    def naive_string_to_date(date_str) do
        case NaiveDateTime.from_iso8601(date_str) do
            {:ok, naive_date} ->
                naive_date
            _reason ->
                TimeUtil.naive_local_now()
        end
    end

end