;; Copyright © 2024 Jaidyn Ann <jadedctrl@posteo.at>
;;
;; This program is free software: you can redistribute it and/or
;; modify it under the terms of the GNU General Public License as
;; published by the Free Software Foundation, either version 3 of
;; the License, or (at your option) any later version.
;;
;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;;
;; You should have received a copy of the GNU General Public License
;; along with this program. If not, see <https://www.gnu.org/licenses/>.


(import
  scheme
  (chicken io)
  (chicken irregex)
  srfi-1
  srfi-130)


;; Splits a string into a list of CRLF’d lines.
(define (unlines lines)
  (string-join lines "\r\n"))


;; Splits a string into a list of CRLF’d lines.
(define (lines string)
  (remove string-null? (string-split string "\r\n")))


;; Splits a line into a cons of the property-string and value-string.
;; … basically splits the string along the first unescaped colon (:).
;;    "apple\:berry:mom:dad" → ("apple\:berry" . "mom:dad")
(define (split-vcard-line line)
  (let [(split (irregex-extract "(\\\\:|[^:])*" line))]
    (if (>= (length split) 2)
        (cons
         (car split)
         ;; Drop the value’s first char (redundant “:”) and concatenate the
         ;; rest of the string-parts which were erroneously split along “:”.
         (string-drop (reduce-right
                       (lambda (a b) (string-concatenate (list a ":" b)))
                       "" (cdr split))
                      1))
        #f)))


;; Splits a key or value-element into its (potentially multiple) parameters.
(define (split-vcard-element key-or-value)
  (irregex-extract "(\\\\;|[^;])*" key-or-value))


;; Parse a line of a vcard file into an alist-friendly format:
;;    (KEY ("keyprop1=d" "keyprop2=b") "VALUE" ("valprop1=a" "valprop2=b"))
(define (parse-vcard-line line)
  (let* [(key-value-strings (split-vcard-line line))
         (key-elements (split-vcard-element (car key-value-strings)))
         (value-elements (split-vcard-element (cdr key-value-strings)))]
    (list (string->symbol (car key-elements))
          (car value-elements)
          (cdr key-elements)
          (cdr value-elements))))


;; Reader thunk. Read/parse an entire vcard into a “vcard alist.”
(define (read-vcard)
  (let [(element (read-vcard-element))]
    (if (not (eof-object? (peek-char)))
        (append (list element) (read-vcard))
        element)))


;; Read a single unfolded line into a vcard “element” list.
(define (read-vcard-element)
  (parse-vcard-line (read-folded-line)))


;; Reader-thunk. Read a “logical” folded-line, where a line beginning with a
;; space is a continuation of the previous line — like with vcards.
(define (read-folded-line)
  (let [(line (read-line))]
    (if (eq? (peek-char) #\space)
        (string-concatenate
         (list line
               (string-drop (read-element) 1)))
        line)))