day_2.rb

module Part2
  #     1
  #   2 3 4
  # 5 6 7 8 9
  #   A B C
  #     D
  class State
    def go_u; self; end
    def go_d; self; end
    def go_l; self; end
    def go_r; self; end

    def to_s
      "State is: #{self.class.to_s.downcase}"
    end
  end

  class One < State # done
    def go_d; Three.new; end
  end

  class Two < State # done
    def go_d; Six.new; end
    def go_r; Three.new; end
  end

  class Three < State # done
    def go_u; One.new; end
    def go_d; Seven.new; end
    def go_l; Two.new; end
    def go_r; Four.new; end
  end

  class Four < State # done
    def go_d; Eight.new; end
    def go_l; Three.new; end
  end

  class Five < State # done
    def go_r; Six.new; end
  end

  class Six < State # done
    def go_u; Two.new; end
    def go_d; A.new; end
    def go_l; Five.new; end
    def go_r; Seven.new; end
  end

  class Seven < State # done
    def go_u; Three.new; end
    def go_d; B.new; end
    def go_l; Six.new; end
    def go_r; Eight.new; end
  end

  class Eight < State
    def go_u; Four.new; end
    def go_l; Seven.new; end
    def go_r; Nine.new; end
    def go_d; C.new; end
  end

  class Nine < State
    def go_l; Eight.new; end
  end

  class A < State
    def go_u; Six.new; end
    def go_r; B.new; end
  end

  class B < State
    def go_u; Seven.new; end
    def go_d; D.new; end
    def go_l; A.new; end
    def go_r; C.new; end
  end

  class C < State
    def go_u; Eight.new; end
    def go_l; B.new; end
  end

  class D < State
    def go_u; B.new; end
  end
end

module Part1
  # 1 2 3
  # 4 5 6
  # 7 8 9

  class State
    def go_u; self; end
    def go_d; self; end
    def go_l; self; end
    def go_r; self; end

    def to_s
      "State is: #{self.class.to_s.downcase}"
    end
  end

  class One < State
    def go_r; Two.new; end
    def go_d; Four.new; end
  end

  class Two < State
    def go_d; Five.new; end
    def go_l; One.new; end
    def go_r; Three.new; end
  end

  class Three < State
    def go_d; Six.new; end
    def go_l; Two.new; end
  end

  class Four < State
    def go_u; One.new; end
    def go_d; Seven.new; end
    def go_r; Five.new; end
  end

  class Five < State
    def go_u; Two.new; end
    def go_d; Eight.new; end
    def go_l; Four.new; end
    def go_r; Six.new; end
  end

  class Six < State
    def go_u; Three.new; end
    def go_d; Nine.new; end
    def go_l; Five.new; end
  end

  class Seven < State
    def go_u; Four.new; end
    def go_r; Eight.new; end
  end

  class Eight < State
    def go_u; Five.new; end
    def go_l; Seven.new; end
    def go_r; Nine.new; end
  end

  class Nine < State
    def go_u; Six.new; end
    def go_l; Eight.new; end
  end
end

LINES = ARGF.readlines.map(&:strip)

def run(initial_state:)
LINES
  .reduce(initial_state) { |initial_line_state, line|
    final_line_state = line.chars.reduce(initial_line_state) { |curr_state, instruction|
      curr_state.public_send("go_#{instruction.downcase}")
    }
    puts "Final line state: #{final_line_state}"
    final_line_state
  }
end

run(initial_state: Part1::Five.new)
run(initial_state: Part2::Five.new)