defmodule Meetup do
  @moduledoc """
  Calculate meetup dates.
  """

  @type weekday ::
          :monday
          | :tuesday
          | :wednesday
          | :thursday
          | :friday
          | :saturday
          | :sunday

  @type schedule :: :first | :second | :third | :fourth | :last | :teenth

  @doc """
  Calculate a meetup date.

  The schedule is in which week (1..4, last or "teenth") the meetup date should
  fall.
  """
  @spec meetup(pos_integer, pos_integer, weekday, schedule) :: :calendar.date()
  def meetup(year, month, weekday, schedule) do
  end
end