class Bottle
  def self.verse(bottles)
    new(bottles).song
  end

  attr_reader :bottles

  def initialize(bottles)
    @bottles = bottles
  end

  def song
    [bottles_message, "\n", take_down_message, "\n"].join
  end

  def bottles_message
    "#{context_bottle(bottles, empty: 'No more bottles')} of beer on the wall, #{context_bottle(bottles)} of beer."
  end

  def take_down_message
    return buy_more_message if bottles == 0

    @bottles -= 1
    "#{context_down} and pass it around, #{context_bottle(bottles)} of beer on the wall."
  end

  def context_bottle(amount, empty: 'no more bottles')
    if amount > 1
      "#{amount} bottles"
    elsif amount == 1
      "#{amount} bottle"
    else
      empty
    end
  end

  def context_down
    bottles > 0 ? "Take one down" : "Take it down"
  end

  def buy_more_message
    "Go to the store and buy some more, 99 bottles of beer on the wall."
  end
end

class Bottles
  def verse(num)
    Bottle.verse(num)
  end

  def verses(top, bottom)
    top.downto(bottom).map { |current| verse(current) }.join("\n")
  end

  def song
    verses(99, 0)
  end
end