fix(03): WR-01 preserve existing RRULE on edit instead of resetting to none

apps/api/src/broker/vevent.ts

@@ -43,6 +43,29 @@ export const RRULE_PRESETS: Record<string, string> = {
   yearly: 'FREQ=YEARLY',
 }
 
+/**
+ * WR-01: Extract the existing RRULE string from a stored VCALENDAR/VEVENT, so the
+ * outbox worker can preserve recurrence on an edit whose payload omits it (the PWA
+ * occurrence contract does not expose recurrence, D-03). Returns the RRULE value as a
+ * 'FREQ=…' string (e.g. 'FREQ=WEEKLY'), or undefined when the event has no RRULE or
+ * the input cannot be parsed.
+ */
+export function extractRruleString(rawVevent: string): string | undefined {
+  let parsed: ReturnType<typeof ICAL.parse>
+  try {
+    parsed = ICAL.parse(rawVevent)
+  } catch {
+    return undefined
+  }
+  const comp = new ICAL.Component(parsed)
+  const vevent = comp.getFirstSubcomponent('vevent')
+  if (!vevent) return undefined
+  const rrule = vevent.getFirstPropertyValue('rrule')
+  if (!rrule) return undefined
+  // ICAL.Recur#toString() yields the RECUR value, e.g. 'FREQ=WEEKLY'.
+  return typeof rrule === 'string' ? rrule : (rrule as ICAL.Recur).toString()
+}
+
 /**
  * Builds a VCALENDAR/VEVENT iCalendar string from form parameters.
  *