(use-modules (ice-9 match)
             (ice-9 rdelim))

(define (read-config path)
  (call-with-input-file path
    (lambda (port)
      (let loop ((line (read-line port)) (acc '()))
        (if (eof-object? line)
            acc
            (match (string-split line #\=)
              ((key-part value-part)
               (let ((key (string->symbol key-part))
                     (value (match value-part
                              ("y" #t)
                              ("n" #f)
                              ("m" 'm)
                              ((? (lambda (x) (string-prefix? "0x" x)))
                               (string->number (substring value-part 2) 16))
                              (_ (call-with-input-string value-part read)))))
                 (loop (read-line port) (cons `(,key . ,value) acc))))
              (_ (loop (read-line port) acc))))))))

(define (kequal? a b)
  (or (equal? a b)
      (and (memq a '(m #t))
           (memq b '(m #t)))))

(match (program-arguments)
  ((_ p1 p2 p3)
   (let ((c1 (read-config p1))
         (c2 (read-config p2))
         (c3 (read-config p3)))
     (for-each (match-lambda
                 ((k2 . v2)
                  (let ((v1 (match (assq k2 c1)
                              ((_ . v1) v1)
                              (#f 'nil)))
                        (v3 (match (assq k2 c3)
                              ((_ . v3) v3)
                              (#f 'nil))))
                    (unless (or (kequal? v1 v2)
                                (kequal? v1 v3))
                      (write `(,k2 ,v1 -> ,v2 / ,v3))
                      (newline)))))
               c2))))