feat: reminder due calculation

app/api/vouchers/route.ts

@@ -2,6 +2,7 @@ import { NextRequest, NextResponse } from "next/server";
 import { getDb } from "@/lib/db";
 import { getVoucherStatus } from "@/lib/voucher-status";
 import { validateVoucher, isExpiringSoon } from "@/lib/vouchers";
+import { parseReminderDays } from "@/lib/reminders";
 
 export async function GET(req: NextRequest) {
   const filter = req.nextUrl.searchParams.get("filter");
@@ -47,6 +48,11 @@ export async function POST(req: NextRequest) {
       kategorie: input.kategorie,
       notiz: input.notiz,
       contacts: contactIds.length ? { create: contactIds.map((contactId) => ({ contactId })) } : undefined,
+      rules: {
+        create: parseReminderDays(
+          typeof body.reminderDays === "string" ? body.reminderDays : Array.isArray(body.reminderDays) ? body.reminderDays.join(",") : undefined
+        ).map((tageVorher) => ({ tageVorher })),
+      },
     },
   });
   return NextResponse.json(created, { status: 201 });

app/vouchers/new/page.tsx

@@ -23,6 +23,7 @@ export default function NewVoucherPage() {
   const [serverError, setServerError] = useState("");
   const [contacts, setContacts] = useState<{ id: number; name: string }[]>([]);
   const [contactIds, setContactIds] = useState<number[]>([]);
+  const [reminderDays, setReminderDays] = useState("30,6,1");
 
   useEffect(() => {
     fetch("/api/contacts")
@@ -55,7 +56,7 @@ export default function NewVoucherPage() {
     const res = await fetch("/api/vouchers", {
       method: "POST",
       headers: { "content-type": "application/json" },
-      body: JSON.stringify({ ...input, contactIds }),
+      body: JSON.stringify({ ...input, contactIds, reminderDays }),
     });
     if (!res.ok) {
       const data = await res.json().catch(() => ({}));
@@ -87,6 +88,20 @@ export default function NewVoucherPage() {
             {errors.includes(f.name) && <p className="mt-1 text-sm text-red-600">Ungültig: {f.name}</p>}
           </div>
         ))}
+        <div>
+          <label htmlFor="reminderDays" className="block text-sm font-medium">
+            Erinnerung (Tage vorher, Kommaliste)
+          </label>
+          <input
+            id="reminderDays"
+            name="reminderDays"
+            type="text"
+            value={reminderDays}
+            onChange={(e) => setReminderDays(e.target.value)}
+            placeholder="30,6,1"
+            className="mt-1 w-full rounded border px-3 py-2"
+          />
+        </div>
         <section id="kontakte">
           <h2 className="text-sm font-medium">Empfänger</h2>
           {contacts.map((c) => (

lib/reminders.ts

@@ -0,0 +1,33 @@
+export const DEFAULT_REMINDER_DAYS = [30, 6, 1];
+
+export function toDateKey(d: Date): string {
+  return `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, "0")}-${String(d.getDate()).padStart(2, "0")}`;
+}
+
+export function dueRulesToday(
+  v: { ablaufdatum: Date | null; status: string },
+  rules: { id: number; tageVorher: number }[],
+  heute: Date
+): number[] {
+  if (v.status !== "aktiv" || !v.ablaufdatum) return [];
+  const out: number[] = [];
+  for (const r of rules) {
+    const ziel = new Date(v.ablaufdatum);
+    ziel.setDate(ziel.getDate() - r.tageVorher);
+    if (toDateKey(ziel) === toDateKey(heute)) out.push(r.id);
+  }
+  return out;
+}
+
+export function idempotencyKey(ruleId: number, kanal: string, empfaenger: string, zielDatum: string): string {
+  return `${ruleId}|${kanal}|${empfaenger}|${zielDatum}`;
+}
+
+export function parseReminderDays(raw: string | null | undefined): number[] {
+  if (raw == null || !raw.trim()) return [...DEFAULT_REMINDER_DAYS];
+  const days = raw
+    .split(",")
+    .map((s) => Number(s.trim()))
+    .filter((n) => Number.isInteger(n) && n >= 0);
+  return [...new Set(days)].sort((a, b) => b - a);
+}

tests/reminders.test.ts

@@ -0,0 +1,17 @@
+import { describe, it, expect } from "vitest";
+import { dueRulesToday, idempotencyKey } from "../lib/reminders";
+describe("dueRulesToday", () => {
+  it("30/6/1 trifft am richtigen Tag", () => {
+    const ablauf = new Date("2026-12-01T00:00:00");
+    const rules = [{ id: 1, tageVorher: 30 }, { id: 2, tageVorher: 6 }, { id: 3, tageVorher: 1 }];
+    expect(dueRulesToday({ ablaufdatum: ablauf, status: "aktiv" }, rules, new Date("2026-11-01T12:00:00"))).toEqual([1]);
+    expect(dueRulesToday({ ablaufdatum: ablauf, status: "aktiv" }, rules, new Date("2026-11-30T08:00:00"))).toEqual([3]);
+  });
+  it("kein Ablaufdatum und eingelöst nie fällig", () => {
+    expect(dueRulesToday({ ablaufdatum: null, status: "aktiv" }, [{ id: 1, tageVorher: 7 }], new Date())).toEqual([]);
+    expect(dueRulesToday({ ablaufdatum: new Date(), status: "eingeloest" }, [{ id: 1, tageVorher: 0 }], new Date())).toEqual([]);
+  });
+  it("key ist stabil", () => {
+    expect(idempotencyKey(1, "mail", "a@b.de", "2026-12-01")).toBe("1|mail|a@b.de|2026-12-01");
+  });
+});