simulator.rb

class Robot
  attr_reader :directions

  def initialize
    @directions = [:north, :east, :south, :west]
  end

  def orient(direction)
    if invalid_direction? direction
      raise ArgumentError
    else
      orient_to direction
    end
  end

  def invalid_direction?(direction)
    !directions.include?(direction)
  end

  def orient_to(direction)
    until self.bearing == direction
      self.turn_right
    end
  end

  def bearing
    directions[0]
  end

  def turn_right
    directions.push directions.shift
  end

  def turn_left
    directions.unshift directions.pop
  end

  def at(x,y)
    @x = x
    @y = y
  end

  def coordinates
    [@x, @y]
  end

  def advance
    case self.bearing
    when :north
      @y += 1
    when :south
      @y -= 1
    when :east
      @x += 1
    when :west
      @x -= 1
    end
  end
end

class Simulator
  INSTRUCTIONS = { turn_left: 'L', turn_right: 'R', advance: 'A' }

  def instructions(commands)
    command_list(commands).map { |command| INSTRUCTIONS.key(command) }
  end

  def command_list(commands)
    commands.split('')
  end

  def place(robot, options ={})
    robot.at(options[:x], options[:y])
    robot.orient(options[:direction])
  end

  def evaluate(robot, commands)
    self.instructions(commands).map { |command| robot.send(command) }
  end
end