99bottles.rb

class Bottles
  def song
    verses(99, 0)
  end

  def verses(from_bottle_count, to_bottle_count)
    from_bottle_count
      .downto(to_bottle_count)
      .map { |c| verse(c) }
      .join("\n")
  end

  def verse(bottle_count)
    line1 = "#{pluralize(bottle_count).capitalize} of beer on the wall, #{pluralize bottle_count} of beer."
    line2 = case bottle_count
            when 0 then "Go to the store and buy some more, 99 bottles of beer on the wall."
            when 1 then "Take it down and pass it around, no more bottles of beer on the wall."
            else "Take one down and pass it around, #{pluralize bottle_count - 1} of beer on the wall."
            end
    "#{line1}\n#{line2}\n"
  end

  private

  def pluralize(bottle_count)
    case bottle_count
    when 0 then "no more bottles"
    when 1 then "1 bottle"
    else "#{bottle_count} bottles"
    end
  end
end