parse dates

dates.ex

defmodule Dates do
  @valid_dates [
                 Date.utc_today() |> Date.to_iso8601(),
                 NaiveDateTime.utc_now() |> NaiveDateTime.to_iso8601(),
                 DateTime.utc_now() |> DateTime.to_iso8601()
               ]
               |> Enum.map(&to_string/1)
               |> Enum.join(" or ")

  @invalid_date_message "Invalid date. Expected formated date. ie #{@valid_dates}"

  def parse_date(nil), do: {:ok, NaiveDateTime.utc_now()}

  def parse_date(input) do
    result =
      with {:error, _} <- NaiveDateTime.from_iso8601(input),
           {:error, _} <- DateTime.from_iso8601(input),
           {:error, _} <- Date.from_iso8601(input) do
        {:error, @invalid_date_message}
      end

    to_naive(result)
  end

  defp to_naive({:ok, %NaiveDateTime{} = date}), do: {:ok, date}
  defp to_naive({:ok, %DateTime{} = date, _offset}), do: {:ok, DateTime.to_naive(date)}

  defp to_naive({:ok, %Date{day: day, month: month, year: year}}) do
    {:ok,
     %NaiveDateTime{
       day: day,
       month: month,
       year: year,
       hour: 0,
       minute: 0,
       second: 0
     }}
  end

  defp to_naive(other), do: other
end