mars_rover_example.rb

# Rover
# - move
# - turn_left
# - turn_right



class Rover
  attr_reader :x, :y, :direction

  COMPASS = %w[N E S W]

  DIRECTION_VECTORS = {
    "N" => [0,1],
    "S" => [0,-1],
    "E" => [1,0],
    "W" => [-1,0],
  }

  def initialize(x,y,direction,width=10,height=10)
    @x, @y, @direction = x, y, direction
    @width, @height = width, height
  end

  def move
    dx, dy = DIRECTION_VECTORS[@direction]

    @x += dx
    @y += dy

    @x = 0       if @x < 0
    @x = @width  if @x > @width
    @y = 0       if @y < 0
    @y = @height if @y > @height
  end

  def turn(n=1)
    pos = COMPASS.index(@direction)
    @direction = COMPASS.rotate(n)[pos]
  end

  def turn_left
    turn(-1)
  end

  def turn_right
    turn(1)
  end

  def read_instruction(i)
    case i
    when "M"
      move
    when "L"
      turn_left
    when "R"
      turn_right
    end

    puts self
  end

  def to_s
    "<Rover: #{x},#{y} facing #{direction}>"
  end

end

r = Rover.new(1,1,"N",5,5)

# r.move
# r.turn_left
# r.turn_right
# r.read_instruction("M")
# r.read_instruction("L")
# r.read_instruction("R")

input = "RMMMMLMMMLRLLLRRRMMM"

input.each_char do |c|
  r.read_instruction(c)
end