Mars rover 🚀 problem

rover.rb

DIRECTIONS = ['N', 'E', 'S', 'W']
CONTROLS = ['L', 'R', 'M']
MOVES = {
  'N' => {'L' => 'W', 'R' => 'E'},
  'E' => {'L' => 'N', 'R' => 'S'},
  'S' => {'L' => 'E', 'R' => 'W'},
  'W' => {'L' => 'S', 'R' => 'N'}
}

class GridError < StandardError; end
class RoverError < StandardError; end

class Grid
  attr_reader :pos_x, :pos_y

  def initialize(pos_x, pos_y)
    @pos_x = pos_x
    @pos_y = pos_y
  end

  def valid?
    pos_x > 0 && pos_y > 0
  end

  def valid!
    raise GridError, "Grid is invalid" unless valid?
  end
end

class Rover
  attr_reader :grid, :start_position
  attr_accessor :pos_x, :pos_y, :direction, :controls

  def initialize(grid)
    @grid = grid
  end

  def move!
    for control in controls do
      if control == 'M'
        puts "Cannot move #{control} ahead." and next unless can_move?
        move
      else
        turn(control)
      end
    end
  end

  def land!(pos_x, pos_y, direction)
    unless pos_x > 0 && pos_x < grid.pos_x && pos_y > 0 && pos_y < grid.pos_y && DIRECTIONS.include?(direction)
      raise("RoverError", "Landed out of the grid!")
    end
    self.start_position = [pos_x, pos_y, direction]
  end

  private

  def start_position=(position)
    @start_position = position
    @pos_x, @pos_y, @direction = position
  end

  def can_move?
    case direction
    when 'N'
      (pos_y + 1) < grid.pos_y
    when 'E'
      (pos_x + 1) < grid.pos_x
    when 'S'
      (pos_y - 1) >= 0
    when 'W'
      (pos_x - 1) >= 0
    else
      false
    end
  end

  def move
    case direction
    when 'N'
      @pos_y += 1
    when 'E'
      @pos_x += 1
    when 'S'
      @pos_y -= 1
    when 'W'
      @pos_x -= 1
    end
  end

  def turn(control)
    @direction = MOVES[direction][control]
  end
end

begin
  puts "Enter the co-ordinates of grid: "
  co_ords = gets.chomp.split.map(&:to_i)
  grid = Grid.new(*co_ords)
  grid.valid!
rescue StandardError
  puts "Grid is is invalid."
  retry
end

while true do
  rover = Rover.new(grid)
  begin
    puts "Enter the landing position of the rover"
    postion = gets.chomp.split

    pos_x = postion[0].to_i
    pos_y = postion[1].to_i
    direction = postion[2]

    rover.land!(pos_x, pos_y, direction)
  rescue StandardError => e
    puts "Invalid landing position."
    retry
  end

  puts "Enter the controls to move the rover (invalid controls will be rejected): "
  rover.controls = gets.chomp.each_char.select{|ch| CONTROLS.include?(ch.upcase)}.map(&:upcase)
  rover.move!
  puts "Rover reached #{rover.pos_x} #{rover.pos_y} #{rover.direction}."

  puts "Do you want to send another rover? (y to continue, press any other key to exit)"
  break unless gets.chomp == "y"
end