99bottles3.ex

defmodule Bottles do
  def song, do: verses(99, 0)

  def verses(first, last) do
    Enum.map_join first..last, "\n", &verse/1
  end

  def verse(number) do
    "#{String.capitalize(containers(number))} of beer on the wall, " <>
    "#{containers(number)} of beer.\n" <>
    "#{action(number)}, " <>
    "#{containers(successor(number))} of beer on the wall.\n"
  end

  defp containers(6), do: "1 six-pack"
  defp containers(number), do: "#{quantity(number)} #{bottles(number)}"

  defp quantity(0), do: "no more"
  defp quantity(number), do: to_string number

  defp bottles(1), do: "bottle"
  defp bottles(_number), do: "bottles"

  defp action(0), do: "Go to the store and buy some more"
  defp action(number), do: "Take #{pronoun(number)} down and pass it around"

  defp pronoun(1), do: "it"
  defp pronoun(_number), do: "one"

  defp successor(0), do: 99
  defp successor(number), do: number - 1
end