(use srfi-13 srfi-1 irregex)

(define (has-abba? str i)
  (and (not (char=? (string-ref str i)
                    (string-ref str (- i 1))))
       (char=? (string-ref str i)
               (string-ref str (- i 3)))
       (char=? (string-ref str (- i 1))
               (string-ref str (- i 2)))))

(define (string-abbas str)
  (let ((abbas '()))
    (string-for-each-index
     (lambda (i)
       (if (and (<= 0 (- i 3)) (has-abba? str i))
           (set! abbas (cons (substring str (- i 3) (+ i 1)) abbas)))) str)
    abbas))

(define (has-aba? str i)
  (and (char=? (string-ref str i)
               (string-ref str (- i 2)))
       (not (char=? (string-ref str i)
                    (string-ref str (- i 1))))))

(define (string-abas str)
  (let ((abas '()))
    (string-for-each-index
     (lambda (i)
       (if (and (<= 0 (- i 2)) (has-aba? str i))
           (set! abas (cons (substring str (- i 2) (+ i 1)) abas)))) str)
    abas))

(define (is-ssl? str)
  (let* ((astrs (irregex-split '(: "[" (* alnum) "]") str))
         (bstrs (irregex-extract '(: "[" (* alnum) "]") str))
         (abas (flatten (map string-abas astrs)))
         (babs (flatten (map string-abas bstrs))))
    (not (null?
          (flatten
           (filter
            (lambda (bab)
              (fold
               (lambda (a b) (or a b)) #f
               (map (lambda (aba)
                      (and (char=? (string-ref bab 0)
                                   (string-ref aba 1))
                           (char=? (string-ref bab 1)
                                   (string-ref aba 0)))) abas))) babs))))))

(define (is-tls? str)
  (call/cc
   (lambda (ret)
     (let ((astrs (irregex-split '(: "[" (* alnum) "]") str))
           (bstrs (irregex-extract '(: "[" (* alnum) "]") str)))
       (and (not (null? (flatten (map string-abbas astrs))))
            (null? (flatten (map string-abbas bstrs))))))))

(define (solvep1 file)
  (with-input-from-file file
    (lambda ()
      (let loop ((l (read-line))
                 (count 0))
        (if (eof-object? l)
            count
            (if (is-tls? l)
                (loop (read-line) (+ count 1))
                (loop (read-line) count)))))))

(define (solvep2 file)
  (with-input-from-file file
    (lambda ()
      (let loop ((l (read-line))
                 (count 0))
        (if (eof-object? l)
            count
            (if (is-ssl? l)
                (loop (read-line) (+ count 1))
                (loop (read-line) count)))))))