Fix FinTS transaction deduplication

convex/bank/fintsMap.test.ts

@@ -0,0 +1,65 @@
+import { describe, expect, test } from "vitest";
+import { mapFinTsTransaction } from "./fintsMap";
+
+const salaryShift = {
+  enabled: true,
+  categoryNames: ["Gehalt & Besoldung"],
+  dayThreshold: 25,
+};
+
+function baseTransaction(overrides: Partial<Parameters<typeof mapFinTsTransaction>[0]> = {}) {
+  return {
+    valueDate: new Date(2026, 5, 22),
+    entryDate: new Date(2026, 5, 22),
+    amount: -12.34,
+    transactionType: "NMSC",
+    bankReference: "",
+    customerReference: "",
+    bookingText: "Kartenzahlung",
+    purpose: "REWE SAGT DANKE",
+    remoteName: "REWE",
+    ...overrides,
+  };
+}
+
+describe("mapFinTsTransaction", () => {
+  test("does not expose MT940 placeholder references as external references", () => {
+    const placeholders = [
+      "NONREF",
+      "NOTPROVIDED",
+      "NOT PROVIDED",
+      "N/A",
+      "POS 13",
+      "POS-42",
+      "POS_1155",
+      "-",
+      "",
+    ];
+
+    for (const placeholder of placeholders) {
+      const mapped = mapFinTsTransaction(
+        baseTransaction({
+          bankReference: placeholder,
+          customerReference: placeholder,
+        }),
+        [],
+        salaryShift,
+      );
+
+      expect(mapped.externalRef).toBeUndefined();
+    }
+  });
+
+  test("keeps real FinTS references for provider-level duplicate detection", () => {
+    const mapped = mapFinTsTransaction(
+      baseTransaction({
+        bankReference: "5J2C21XL0470L56V/39761",
+        customerReference: "NONREF",
+      }),
+      [],
+      salaryShift,
+    );
+
+    expect(mapped.externalRef).toBe("5J2C21XL0470L56V/39761");
+  });
+});

convex/bank/fintsMap.ts

@@ -14,6 +14,54 @@ export type FintsStatementTransaction = {
   customerReference?: string;
 };
 
+const FINTS_EXTERNAL_REF_PLACEHOLDERS = new Set([
+  "0",
+  "00",
+  "000",
+  "0000",
+  "00000",
+  "000000",
+  "0000000",
+  "00000000",
+  "000000000",
+  "0000000000",
+  "KEINE",
+  "N/A",
+  "NA",
+  "NONE",
+  "NONREF",
+  "NOREF",
+  "NOTPROVIDED",
+  "NULL",
+  "UNBEKANNT",
+]);
+
+function normalizeFinTsExternalRefValue(value?: string): string | undefined {
+  const trimmed = value?.trim();
+  if (!trimmed) return undefined;
+
+  const compact = trimmed.replace(/[\s_-]+/g, "").toUpperCase();
+  if (
+    !compact ||
+    FINTS_EXTERNAL_REF_PLACEHOLDERS.has(compact) ||
+    /^POS\d+$/.test(compact)
+  ) {
+    return undefined;
+  }
+
+  return trimmed;
+}
+
+export function normalizeFinTsExternalRef(
+  bankReference?: string,
+  customerReference?: string,
+): string | undefined {
+  return (
+    normalizeFinTsExternalRefValue(bankReference) ??
+    normalizeFinTsExternalRefValue(customerReference)
+  );
+}
+
 export function formatFinTsDate(date: Date): string {
   const y = date.getFullYear();
   const m = String(date.getMonth() + 1).padStart(2, "0");
@@ -55,7 +103,7 @@ export function mapFinTsTransaction(
     vorgang,
     isPending: false,
     rawText: rawText || undefined,
-    externalRef: tx.bankReference || tx.customerReference || undefined,
+    externalRef: normalizeFinTsExternalRef(tx.bankReference, tx.customerReference),
     categoryName,
     assignedMonth,
     effectiveMonth,