99-bottles.exs

defmodule BeerSong do
  @moduledoc """
  This showcases recursion, pattern-matching, multi-line strings,
  default arguments, embedded docs and pipes.
  """
  import String, only: [downcase: 1]

  @drink "Take one down and pass it around"
  @no_beer "Go to the store and buy some more"

  def sing(beers) when beers < 0, do: :the_end

  def sing(beers \\ 99) do
    beers
    |> song
    |> lyrics
    |> IO.puts

    sing(beers - 1)
  end

  defp lyrics({count, next_count, phrase}) do
    """
    #{count} of beer on the wall, #{downcase(count)} of beer. 
    #{phrase}, #{next_count} of beer on the wall.
    """
  end

  defp song(0), do: {"No more bottles", "99 bottles", @no_beer}
  defp song(1), do: {"1 bottle", "no more bottles", @drink}
  defp song(2), do: {"2 bottles", "1 bottle", @drink}
  defp song(beers), do: {"#{beers} bottles", "#{beers - 1} bottles", @drink}
end