Ruby Mars Rover

rover.rb

class Rover
  # attr_reader :x, :y, :direction
  def initialize(x, y, dir)
    @x = x
    @y = y
    @dir = dir
  end

  def to_s
    puts "#{@x} #{@y} #{@dir}"
  end

  def command(s)
    s.split('').each do |cmd|
      if cmd == 'M' # move
        case @dir
        when 'N'
          @y += 1
        when 'S'
          @y -= 1
        when 'W'
          @x -= 1
        when 'E'
          @x += 1
        end
      else # turn
        dir = Direction.new(@dir)
        case cmd
        when 'L'
          @dir = dir.turn_left
        when 'R'
          @dir = dir.turn_right
        end
      end
    end
    puts self
  end

end

class Direction
  DIRECTION = ['N','E','S','W']

  def initialize(dir)
    @i = DIRECTION.find_index {|d| d == dir}
  end
  def turn_left
    @i -= 1
    @i = 3 if @i < 0
    return DIRECTION[@i]
  end
  def turn_right
    @i += 1
    @i = 0 if @i > 3
    return DIRECTION[@i]
  end
end

# Test Input:
rover = Rover.new(1, 2, 'N')
rover.command('M')
# Expected Output:
# 1 3 N
# Test Input:
rover = Rover.new(1, 2, 'N') 
rover.command('LMLMLMLMM')
# Expected Output:
# 1 3 N
# Test Input:
rover = Rover.new(3, 3, 'E')
rover.command('MMRMMRMRRM')
# Expected Output:
# 5 1 E