kata_bowling_game.rb

class Game
  def initialize
    @rolls = Array.new(21) {0}
    @current_roll = 0
  end

  def roll(pins)
    @rolls[@current_roll] = pins
    @current_roll += 1
  end
  
  def score
    total_score = 0
    roll_index = 0
    
    10.times do
      if is_strike? roll_index
        total_score += 10 + get_strike_bonus(roll_index)
        roll_index += 1
      elsif is_spare? roll_index
        total_score += 10 + get_spare_bonus(roll_index)
        roll_index += 2
      else
        total_score += get_frame_score(roll_index)
        roll_index += 2
      end
    end
    
    total_score
  end

  private
  
  @rolls
  @current_roll

  def is_spare?(roll_index)
    get_frame_score(roll_index) == 10
  end
  
  def is_strike?(roll_index)
    @rolls[roll_index] == 10
  end
  
  def get_strike_bonus roll_index
    get_frame_score(roll_index+1)
  end
  
  def get_spare_bonus frame
    @rolls[frame*2+2]
  end
  
  def get_frame_score roll_index
    @rolls[roll_index] + @rolls[roll_index+1]
  end
end