;;; random.ss
;;; A connect-5 player who simply moves to a random unoccupied location.
;;;

;; An on/off switch for any debugging statements.
(define debugging-on false)
(define program-name "random.ss") ; used in debugging.

;; debug: string, strings... --> (void)
;; Print a message (via printf) to stderr, if debugging-on.
;; (We can't print to stdout -- the referee awaits an answer there.)
;;
(define (debug msg . args)
  (when debugging-on
     (let* {[msg-w-src (string-append program-name " debug: " msg "~n")]
            [arg-list  (cons msg-w-src args)]  ; The list of arguments for printf.
            [full-msg-string (apply format arg-list)]}
     (fprintf (current-error-port) full-msg-string))))



;; unoccupied? : symbol --> boolean
;; Is 
(define (unoccupied? content) (symbol=? content '-))

;(boolean=? (unoccupied? '-)  true)
;(boolean=? (unoccupied? 'X)  false)
;(boolean=? (unoccupied? 'O)  false)
;(boolean=? (unoccupied? 'kiwi-fruit-with-the-skin-still-on)  false)



(define check-for-occupied true)

(define (a-random-location board)
  (local [(define rows (length board))
          (define cols (length (first board)))
          (define a-row (random rows))
          (define a-col (random cols))]
     (if (or (not check-for-occupied)
             (unoccupied? (list-ref (list-ref board a-row) a-col)))
         (list a-col a-row)
         (a-random-location board))
         ))


; Compute the answer, then print it:
;
(printf "~s~n" (a-random-location (read)))

#|
(define board (read))
(debug "Read the board: ~s." board)

(define answer (a-random-location board))
(debug "Returning answer ~s." answer)
(printf "~s~n" answer)
|#