Add NORMALIZE-VCARD; ensure a vCard alist’s legal

vcarded.scm

@@ -14,7 +14,7 @@
 ;; along with this program. If not, see <https://www.gnu.org/licenses/>.
 
 (module vcarded
-    (read-vcard write-vcard)
+    (read-vcard write-vcard normalize-vcard)
 
   (import
     scheme
@@ -88,6 +88,33 @@
               vcard-alist))
 
 
+  ;; Returns a “normalized” version of the given VCARD-ALIST.
+  ;; Will make sure that required properties (“BEGIN” and “END”) are included,
+  ;; and optionally update the PRODID and VERSION properties.
+  (define (normalize-vcard vcard-alist #!optional
+                           (update-prod-id? #t) (update-version? #t))
+    (let ([empty-alist? (or (null? vcard-alist)
+                            (eq? (length vcard-alist) 1))])
+      (when update-version?
+        (set! vcard-alist
+          (alist-update 'VERSION (list '() "4.0") vcard-alist)))
+      (when update-prod-id?
+        (set! vcard-alist
+          (alist-update 'PRODID (list '() ".//jadedctrl//chicken-vcarded") vcard-alist)))
+      (when (or empty-alist?
+                (not (eq? (caar vcard-alist) 'BEGIN)))
+        (set! vcard-alist
+          (append '((BEGIN () "VCARD"))
+                  (remove (lambda (a) (eq? (car a) 'BEGIN))
+                          vcard-alist))))
+      (when (or empty-alist?
+                (not (eq? (car (last vcard-alist)) 'END)))
+        (set! vcard-alist
+          (append
+           (remove (lambda (a) (eq? (car a) 'END)) vcard-alist)
+           '((END () "VCARD")))))
+      vcard-alist))
+
 
   ;;; ~ vCard parsing [string→alist] ~