Improve family invitations and absence management flows

src/lib/absence-policy.ts

@@ -0,0 +1,37 @@
+// Absences are calendar dates stored as UTC dates, independent of the server timezone.
+export function absenceDate(value: string) {
+  if (!/^\d{4}-\d{2}-\d{2}$/.test(value)) throw new Error("Ungültiges Datum.");
+  const date = new Date(`${value}T00:00:00.000Z`);
+  if (Number.isNaN(date.getTime()) || date.toISOString().slice(0, 10) !== value)
+    throw new Error("Ungültiges Datum.");
+  return date;
+}
+
+export function isAbsenceDate(value: string) {
+  try {
+    absenceDate(value);
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+export function absenceToday(now = new Date()) {
+  const parts = new Intl.DateTimeFormat("en-CA", {
+    timeZone: "Europe/Berlin",
+    year: "numeric",
+    month: "2-digit",
+    day: "2-digit",
+  }).formatToParts(now);
+  const part = (type: string) =>
+    parts.find((item) => item.type === type)!.value;
+  return `${part("year")}-${part("month")}-${part("day")}`;
+}
+
+export function canManageKitaAbsences(role: string) {
+  return ["ADMIN", "KOORDINATOR", "ERZIEHER"].includes(role);
+}
+
+export function canEditOwnAbsence(startDate: string, today: string) {
+  return startDate > today;
+}