defmodule BottleSong do
  @moduledoc """
  Handles lyrics of the popular children song: Ten Green Bottles
  """

  defp verse(n) do
    bottle_sense = fn
      0 -> "No green bottles"
      1 -> "One green bottle"
      2 -> "Two green bottles"
      3 -> "Three green bottles"
      4 -> "Four green bottles"
      5 -> "Five green bottles"
      6 -> "Six green bottles"
      7 -> "Seven green bottles"
      8 -> "Eight green bottles"
      9 -> "Nine green bottles"
      10 -> "Ten green bottles"
    end

    "#{bottle_sense.(n)} hanging on the wall,\n#{bottle_sense.(n)} hanging on the wall,\nAnd if one green bottle should accidentally fall,\nThere'll be #{String.downcase(bottle_sense.(n-1))} hanging on the wall."
  end

  @spec recite(pos_integer, pos_integer) :: String.t()
  def recite(start_bottle, take_down) do
    Enum.map_join(0..(take_down - 1), "\n\n", &verse(start_bottle - &1))
  end
end