initial commit

src/lib/format.ts

@@ -0,0 +1,41 @@
+import { format as dfFormat } from "date-fns";
+import { de } from "date-fns/locale";
+
+export const eur = new Intl.NumberFormat("de-DE", {
+  style: "currency",
+  currency: "EUR",
+});
+
+export const pct = new Intl.NumberFormat("de-DE", {
+  style: "percent",
+  minimumFractionDigits: 1,
+  maximumFractionDigits: 1,
+});
+
+export function formatDate(date: Date | string | undefined): string {
+  if (!date) return "–";
+  const d = typeof date === "string" ? new Date(date) : date;
+  return dfFormat(d, "dd.MM.yyyy", { locale: de });
+}
+
+export function formatMonth(monthKey: string | undefined): string {
+  if (!monthKey) return "–";
+  const [year, month] = monthKey.split("-");
+  return `${month}.${year}`;
+}
+
+export function formatAmount(amount: number): string {
+  if (amount === 0) return eur.format(0);
+  return eur.format(amount);
+}
+
+export function amountClass(amount: number): string {
+  if (amount < 0) return "text-red-600 dark:text-red-400";
+  if (amount > 0) return "text-emerald-600 dark:text-emerald-400";
+  return "";
+}
+
+export function dashIfZero(value: number, formatter: (n: number) => string = (n) => String(n)): string {
+  if (value === 0) return "–";
+  return formatter(value);
+}