bcdice_v3.rb

module BCDice  
  VERSION = "3.0.0b"
  
  # @return [Class]
  def self.game_system_class(id)
    # ...
  end
end

class BCDice::GameSystem::Base  
  def initialize
    @randomizer = Randomizer.new
    @secret = false
  end
  
  def id
    self.class::ID
  end
  
  def name
    self.class::NAME
  end
  
  # @return [String, nil]
  def eval(command)
    @secret = match_secret?(command)
    res = eval_game_system_specific_command(command)
    if res
      return res
    end

    [AddDice, RerollDice, Choice].each do |klass|
      common = klass.new(@randomizer, this)
      res = common.eval(command)
      if res
        return res
      end
    end

    return nil
  end
  
  # @return [Boolean]
  def secret?
    @secret
  end
  
  # @return [Array<Array<(Integer, Integer)>>]
  def rand_results
    @randomizer.rand_results
  end
  
  private
  
  # @return [nil]
  def eval_game_system_specific_command(command); end
end

def BCDice::GameSystem::Cthulhu < BCDice::GameSystem::Base
  ID = "Cthulhu"
  NAME = "クトゥルフ神話"
  
  private
  
  # @return [String]
  # @return [nil]
  def eval_game_system_specific_command(command)
    if command.start_with?("CC")
      return skill_check(command)
    else
      return nil
    end
  end
  
  # @return [String]
  def skill_check(command)
    value = roll_d(1, 100)
    
    m = /^CC<=(\d+)$/.match(command)
    if m
      target = m[1].to_i
      suffix = value <= target ? "成功" : "失敗"
      return ":(1D100) ＞ #{value} ＞ #{suffix}"
    else
      return ":(1D100) ＞ #{value}"
    end
  end
end

class AddDice
  def initialize(randomizer, game_system)
    @randomizer = randomizer
    @game_system = game_system
  end

  # @return [String]
  # @return [nil]
  def eval(command)
    #
  end
end

game_system_class = BCDice.game_system_class("Cthulhu") #=> BCDice::GameSystem::Cthulhu
game_system_class.ID #=> "Cthulhu"
game_system_class.NAME #=> "クトゥルフ神話"
game_system_class.HELP_MESSAGE #=> ...
game_system = game_system_class.new
game_system.eval("CC<=70 目星") #=> "(1D100) ＞ 60 ＞ 成功"
game_system.eval("1D6 SANチェック") #=> "(1D6) ＞ 5"
game_system.eval("2B6") #=> "(2B6) ＞ [5,2]"
game_system.secret? #=> false
game_system.id #=> "Cthulhu"
game_system.name #=> "クトゥルフ神話"
game_system.help_message #=> ...