Robot Simulator

simulator.rb

class Robot
  attr_accessor :bearing, :coordinates
  
  def orient(direction)
    if [:north, :east, :south, :west].include? direction
      self.bearing = direction
    else
      raise ArgumentError, "Invalid direction"
    end
  end

  def turn_right
    turn('r')
  end
  
  def turn_left
    turn('l')
  end
  
  def advance
    case bearing
      when :north then self.coordinates[1] += 1
      when :east then self.coordinates[0] += 1
      when :south then self.coordinates[1] -= 1
      when :west then self.coordinates[0] -= 1
    end
  end
  
  def at(x, y)
    self.coordinates = [x, y]
  end
  
  private
    
    def turn(direction)
      if direction == 'r'
        case bearing
          when :north then self.bearing = :east
          when :east then self.bearing = :south
          when :south then self.bearing = :west
          when :west then self.bearing = :north
        end
      else
        case bearing
          when :north then self.bearing = :west
          when :east then self.bearing = :north
          when :south then self.bearing = :east
          when :west then self.bearing = :south
        end
      end
    end
end

class Simulator
  
  def place(robot, args)
    robot.at(args[:x], args[:y])
    robot.orient(args[:direction])
  end
  
  def evaluate(robot, input_commands)
    instructions(input_commands).each do |action|
      case action
        when :turn_right then robot.turn_right
        when :turn_left then robot.turn_left
        when :advance then robot.advance
      end
    end
  end
  
  def instructions(input_commands)
    input_commands.split('').map do |command|  
      case command
        when 'R' then :turn_right
        when 'L' then :turn_left
        when 'A' then :advance
      end
    end
  end
end