(in-package #:json)

(defparameter number-parser
  (let ((signed-digits
          (comp ((sign (zero-or-one (unit (lambda (x) (or (char= x #\-)
                                                          (char= x #\+))))))
                 (natural (one-or-more (unit #'digit-char-p))))
            (cons sign natural))))
    (comp ((base (either signed-digits
                         (fail "Malformed number.")))
           (dot (zero-or-one (unit (lambda (x) (char= x #\.)))))
           (fraction (if dot
                       (either (one-or-more (unit #'digit-char-p))
                               (fail "Malformed fractional part."))
                       nothing))
           (e (zero-or-one (unit (lambda (x) (or (char= x #\e)
                                                 (char= x #\E))))))
           (exponent (if e
                       (either signed-digits
                               (fail "Malformed exponent part."))
                       nothing)))
      (list 'number base fraction exponent))))

(defparameter string-parser
  (comp ((start (unit (lambda (x) (char= x #\"))))
         (chars (zero-or-more (either (comp ((slash (unit (lambda (x) (char= x #\\))))
                                             (escaped (unit))
                                             (codepoints (if (and escaped (char= escaped #\u))
                                                           (comp ((cp0 (unit #'digit-char-p))
                                                                  (cp1 (unit #'digit-char-p))
                                                                  (cp2 (unit #'digit-char-p))
                                                                  (cp3 (unit #'digit-char-p)))
                                                             (let ((str (make-string 4)))
                                                               (setf (char str 0) cp0)
                                                               (setf (char str 1) cp1)
                                                               (setf (char str 2) cp2)
                                                               (setf (char str 3) cp3)
                                                               str))
                                                           nothing)))
                                        (case escaped
                                          (#\n
                                           #\Newline)
                                          (#\t
                                           #\Tab)
                                          (#\u
                                           codepoints)
                                          (t escaped)))
                                      (unit (lambda (x) (char/= x #\"))))))
         (end (unit (lambda (x) (char= x #\")))))
    (list 'string chars)))