robot_name.rb

class Robot
  NAME_LETTERS = ("A".."Z").to_a
  NAME_NUMBERS = (100..999).to_a

  attr_accessor :name

  def initialize
    reset
  end

  def reset
    self.name = build_robot_name
  end

  private

  def build_robot_name
    firstname = NAME_LETTERS.product(NAME_LETTERS).sample
    lastname = NAME_NUMBERS.sample
    name_generator(firstname, lastname)
  end

  def name_generator(firstname, lastname)
    remove_name_combinations(firstname, lastname)
    firstname.join('') + lastname.to_s
  end

  def remove_name_combinations(firstname, lastname)
    remove_firstname(firstname)
    remove_lastname(lastname)
  end

  def remove_firstname(firstname)
    firstname.each do |letter|
      NAME_LETTERS.delete(letter)
    end
  end

  def remove_lastname(lastname)
    NAME_NUMBERS.delete(lastname)
  end
end