ADD: changed to rect router

app/lib/tax.ts

@@ -0,0 +1,40 @@
+export const TAX_RATES = [
+  { label: "19% MwSt. (Regelsteuersatz)", value: 19 },
+  { label: "7% MwSt. (ermäßigt)", value: 7 },
+  { label: "0% (steuerfrei / §13b UStG)", value: 0 },
+] as const;
+
+export function calcItemAmounts(
+  quantity: number,
+  unitPrice: number,
+  taxRate: number
+) {
+  const netAmount = Math.round(quantity * unitPrice * 100) / 100;
+  const taxAmount = Math.round(netAmount * (taxRate / 100) * 100) / 100;
+  const grossAmount = Math.round((netAmount + taxAmount) * 100) / 100;
+  return { netAmount, taxAmount, grossAmount };
+}
+
+export function calcInvoiceTotals(
+  items: Array<{ netAmount: number; taxAmount: number; grossAmount: number }>
+) {
+  const netTotal = items.reduce((sum, i) => sum + i.netAmount, 0);
+  const taxTotal = items.reduce((sum, i) => sum + i.taxAmount, 0);
+  const grossTotal = items.reduce((sum, i) => sum + i.grossAmount, 0);
+  return {
+    netTotal: Math.round(netTotal * 100) / 100,
+    taxTotal: Math.round(taxTotal * 100) / 100,
+    grossTotal: Math.round(grossTotal * 100) / 100,
+  };
+}
+
+export function formatCurrency(amount: number | string): string {
+  return new Intl.NumberFormat("de-DE", {
+    style: "currency",
+    currency: "EUR",
+  }).format(Number(amount));
+}
+
+export function formatDate(date: Date | string): string {
+  return new Intl.DateTimeFormat("de-DE").format(new Date(date));
+}