bottles.exs

defmodule Bottles do
  def verses(from, to) do
    Enum.map_join(from..to, "\n", &verse(&1))
  end

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

  def song do
    verses(99, 0)
  end

  defp action(0), do: "Go to the store and buy some more, 99 bottles of beer on the wall"
  defp action(n), do: "Take #{it_or_one(n)} down and pass it around, #{bottles_left(n)} of beer on the wall"

  defp pluralise_bottle(1), do: "bottle"
  defp pluralise_bottle(_), do: "bottles"

  defp it_or_one(1), do: "it"
  defp it_or_one(_), do: "one"

  defp bottles_of_beer_on_the_wall(0), do: "no more bottles"
  defp bottles_of_beer_on_the_wall(n), do: "#{n} #{pluralise_bottle(n)}"

  defp bottles_left(1), do: "no more bottles"
  defp bottles_left(2), do: "1 bottle"
  defp bottles_left(n), do: "#{n-1} bottles"
end