Start adding serializing vCard alists into strings

vcarded.scm

@@ -148,7 +148,9 @@
             (list date-prop
                   string->any-date
                   (lambda (datetime)
-                    (date->string datetime "~Y~m~dT~H~M~S~z"))))
+                    (if (date? datetime)
+                        (date->string datetime "~Y~m~dT~H~M~S~z")
+                        datetime))))
           vcard-datetime-properties)
      (map (lambda (csv-prop)
              (list csv-prop
@@ -199,11 +201,17 @@
             (string-split string delimiter)))))
 
 
-  (define (parse-vcard-prop property elements)
+  ;; Given a vCard property and its values (e.g., “VERSION” and “3.0”),
+  ;; parse them into a list.
+  ;;    “EMAIL;TYPE=home” "mom@dad.com” → '(EMAIL ("TYPE=home") "mom@dad.com")
+  (define (parse-vcard-property property elements)
     (append (list property)
             (list elements)))
 
 
+  ;; Given the value(s) of a vCard element’s value string(s), returned a
+  ;; parsed object.
+  ;;    'BIRTHDAY "2024-01-02T00:00:00" → #@2024-01-02T00:00:00-0600
   (define (parse-vcard-value prop elements)
     (let [(parser-and-unparser-funcs (alist-ref prop vcard-value-parsers))]
       (if parser-and-unparser-funcs
@@ -213,6 +221,30 @@
           (list elements))))
 
 
+  ;; With an element of a parsed vCard alist, serialize it (back) into a
+  ;; string.
+  (define (serialize-vcard-element element)
+    (let [(property (string-join
+                     (append (list (symbol->string (car element)))
+                             (second element)) ";"))
+          (value (serialize-vcard-value (car element) (last element)))]
+      (string-join (list property value) ":")))
+
+
+  ;; Serialize the value of a vCard property (from a parsed vCard alist)
+  ;; into a string.
+  (define (serialize-vcard-value prop value)
+   (let [(parser-and-unparser-funcs (alist-ref prop vcard-value-parsers))]
+     (if parser-and-unparser-funcs
+         (apply (cadr parser-and-unparser-funcs) (list value))
+         value)))
+
+
+  ;; Serialize a vCard parsed-alist into a set of line-strings, once more.
+  (define (serialized-vcard vcard-alist)
+    (map serialize-vcard-element vcard-alist))
+
+
   ;; 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)
@@ -220,7 +252,7 @@
            (prop-elements (string-split-unescaped (car prop-value-strings) ";"))
            (value-elements (cdr prop-value-strings))
            (property (string->symbol (string-upcase (car prop-elements))))]
-      (append (parse-vcard-prop property (cdr prop-elements))
+      (append (parse-vcard-property property (cdr prop-elements))
               (parse-vcard-value property value-elements))))