robots! ruby!

robot.rb

class Robot

  DIRECTIONS = {
    1 => "NORTH",
    2 => "EAST",
    3 => "SOUTH",
    4 => "WEST"
  }

  attr_accessor :grid_size, :x, :y, :facing

  def initialize grid_size
    @grid_size = grid_size
  end

  def parse_input str
    str.split("\n").each do |line|
      cmd, args = line.split(" ")
      args = args.to_s.split(",")
  
      self.send cmd.downcase.to_sym, *args
    end
  end

  def left
    rotate -1
  end

  def right
    rotate +1
  end

  def rotate modifier
    return unless placed?

    idx = DIRECTIONS.key(facing)

    next_dir_idx = idx + modifier
    next_dir_idx = 1 if next_dir_idx > 4 
    next_dir_idx = 4 if next_dir_idx < 1

    @facing = DIRECTIONS[next_dir_idx]
  end

  def move
    return unless placed?

    x_, y_ = x, y

    case facing
    when "NORTH"
      y_ = y + 1
    when "SOUTH"
      y_ = y - 1
    when "EAST"
      x_ = x + 1
    when "WEST"
      x_ = x - 1
    end

    if valid_move?(x_, y_)
      @x = x_
      @y = y_
    end
  end

  def place x, y, direction
    x = x.to_i
    y = y.to_i

    return unless valid_move?(x, y) && valid_direction?(direction)

    @x = x
    @y = y
    @facing = direction
  end

  def report
    return [x, y, facing].join(",")
  end

  def placed?
    !x.nil? && !y.nil?
  end

  def valid_move? x, y
    return (0...grid_size-1) === x && (0...grid_size-1) === y
  end

  def valid_direction? direction
    return DIRECTIONS.values.include?(direction)
  end
end