Freakenstein code

meetup.exs

defmodule Meetup do

  defmacrop dayname_parts, do: %W(mon tues wednes thurs fri satur sun)

  defmacrop dayname(range_id, dayname_part) do
    if (range_id == :teenth) do
  	  dayname_part <> "teenth"
  	else
  	  bin = atom_to_binary(range_id)
  	  bin <> "_" <> dayname_part <> "day"
  	end
  	 |> binary_to_atom
  end

  defp range(:teenth,_month,_year), do: 13..19
  defp range(:first ,_month,_year), do: 1..7
  defp range(:second,_month,_year), do: 8..14
  defp range(:third ,_month,_year), do: 15..21
  defp range(:forth ,_month,_year), do: 22..28
  defp range(:last  , month, year), do: last_7_days(month,year)

  defp last_7_days(month,year) do
  	last_day = :calendar.last_day_of_the_month(year, month)
  	last_day-6..last_day
  end

  defp day_of_the_week(range_id,day_of_the_week,month,year) do
    range(range_id,month,year)
      |> Enum.map(&({year,month,&1}))
      |> Enum.filter(&(:calendar.day_of_the_week(&1)==day_of_the_week))
      |> Enum.first()
  end

  defmacrop def_dates_for_range(range_id) do
  	dayname_parts()
  	  |> Enum.with_index()
  	  |> Enum.map(fn {index,dayname_part} -> {index+1,dayname(range_id,dayname_part)} end)
  	  |> Enum.map(fn {day_index, function_name}-> 
  	  	  quote do
  	  		def unquote(function_name)(month, year) do
  		  	  day_of_the_week(range_id, unquote(day_index), month, year)
  		  	end
  		  end
  		end)
  end

  def_dates_for_range(:teenth)
  def_dates_for_range(:first)
  def_dates_for_range(:second)
  def_dates_for_range(:third)
  def_dates_for_range(:forth)
  def_dates_for_range(:last)
  
end