(define (get-word text-port)
  (let loop [(w '())]
    (let [(c (get-char text-port))]
      (if (or (eof-object? c) (char-whitespace? c))
	(list->string (reverse w))
	(loop (cons c w))))))

(let [(file (open-input-file "day-2.input"))]
  (let loop [(x 0) (y 0)]
    (let [(amount (string->number (get-word file)))
	  (move (get-word file))]
      (cond
	((string=? move "forward")
	 (loop (+ x amount) y))
	((string=? move "down")
	 (loop x (+ y amount)))
	((string=? move "up")
	 (loop x (- y amount)))
	(else
	  (display "part 1: ")
	  (display (* x y))
	  (newline))))))

(let [(file (open-input-file "day-2.input"))]
  (let loop [(x 0) (y 0) (aim 0)]
    (let [(amount (string->number (get-word file)))
	  (move (get-word file))]
      (cond
	((string=? move "forward")
	 (loop 
	   (+ x amount) 
	   (+ y (* aim amount))
	   aim))
	((string=? move "down")
	 (loop x y (+ aim amount)))
	((string=? move "up")
	 (loop x y (- aim amount)))
	(else
	  (display "part 2: ")
	  (display (* x y))
	  (newline))))))