fix(web): prefill birthday in contact form for imported contacts

internal/web/contacts.go

@@ -14,7 +14,9 @@ import (
 	"sort"
 	"strconv"
 	"strings"
+	"time"
 
+	"git.arnef.de/arnef/nidus/internal/birthdays"
 	"git.arnef.de/arnef/nidus/internal/store"
 	"git.arnef.de/arnef/nidus/internal/web/templates"
 	vcard "github.com/emersion/go-vcard"
@@ -490,6 +492,27 @@ func photoDataURL(card vcard.Card) string {
 	return ""
 }
 
+// birthdayInputValue returns birthday in the "YYYY-MM-DD" form the contact
+// form's <input type="date"> renders. vCards from other clients often store
+// the date in vCard 3.0's compact "YYYYMMDD" form or year-less "--MMDD"
+// form; a browser date input silently ignores values it can't parse, which
+// would leave the field looking empty and drop the birthday on the next
+// save. A year-less value can't be shown in a year-bearing date input as-is,
+// so it's pre-filled with the current year — the field still shows the
+// contact's real month/day (never the blank state the bug produced), and the
+// user can correct the year if they know it. Unrecognized values pass
+// through unchanged (the empty string for contacts without a birthday).
+func birthdayInputValue(birthday string) string {
+	month, day, year, ok := birthdays.ParseBirthday(birthday)
+	if !ok {
+		return birthday
+	}
+	if year == 0 {
+		year = time.Now().Year()
+	}
+	return fmt.Sprintf("%04d-%02d-%02d", year, int(month), day)
+}
+
 func labeledValues(card vcard.Card, key string) []templates.LabeledValue {
 	fields := card[key]
 	out := make([]templates.LabeledValue, 0, len(fields))
@@ -541,7 +564,7 @@ func contactFormFromCard(book, id string, data []byte) (templates.ContactFormDat
 		Surname:      surname,
 		Organization: card.PreferredValue(vcard.FieldOrganization),
 		Note:         card.PreferredValue(vcard.FieldNote),
-		Birthday:     card.PreferredValue(vcard.FieldBirthday),
+		Birthday:     birthdayInputValue(card.PreferredValue(vcard.FieldBirthday)),
 		PhotoDataURL: photoDataURL(card),
 		Phones:       ensureAtLeastOne(labeledValues(card, vcard.FieldTelephone)),
 		Emails:       ensureAtLeastOne(labeledValues(card, vcard.FieldEmail)),