# works on things turning and moving
class Grid
  attr_accessor :x, :y

  def at(x, y)
    self.x = x
    self.y = y
  end

  def coordinates
    [x, y]
  end

  def advance(bearing)
    self.y += 1 if bearing == :north
    self.y -= 1 if bearing == :south
    self.x += 1 if bearing == :east
    self.x -= 1 if bearing == :west
  end
end

# can orient and move
class Robot
  DIRECTIONS = [:north, :east, :south, :west].freeze
  attr_accessor :bearing, :grid

  def initialize
    @grid = Grid.new
  end

  def place(args = {})
    x         = args[:x]
    y         = args[:y]
    direction = args[:direction]

    at(x, y)
    self.bearing = direction
    self
  end

  def orient(direction)
    raise ArgumentError unless DIRECTIONS.include? direction
    self.bearing = direction
  end

  def turn_right
    current_index = DIRECTIONS.index(bearing)
    next_indext   = (current_index + 1) % 4
    self.bearing  = DIRECTIONS[next_indext]
  end

  def turn_left
    current_index = DIRECTIONS.index(bearing)
    next_indext   = (current_index - 1)
    self.bearing  = DIRECTIONS[next_indext]
  end

  def at(x, y)
    grid.at(x, y)
  end

  def coordinates
    grid.coordinates
  end

  def advance
    grid.advance(bearing)
  end
end

# handles instructions for robot
class Simulator
  DICTIONARY = { 'L' => :turn_left,
                 'R' => :turn_right,
                 'A' => :advance }.freeze

  def instructions(command_string)
    command_string.chars.map do |letter|
      DICTIONARY[letter]
    end
  end

  def place(robot, args = {})
    robot.place(args)
  end

  def evaluate(robot, command_string)
    instructions = instructions(command_string)
    instructions.each do |instruction|
      robot.send(instruction)
    end
  end
end