fix: import identical JSON transactions

backend/src/services/import.integration.test.ts

@@ -8,6 +8,12 @@ const makeStatement = (sourceIds: string[]) => ({
   transactions: sourceIds.map((sourceId) => ({ operationAt: '2026-08-20T10:00:00+03:00', amountSigned: 100, commission: 0, description: 'Пополнение', sourceId })),
 });
 
+const duplicateStatement = {
+  schemaVersion: '1.0', bank: 'TEST',
+  statement: { accountNumber: 'fingerprint-test', currency: 'RUB', openingBalance: 0, closingBalance: 200, exportedAt: '2026-08-20T12:00:00+03:00' },
+  transactions: Array.from({ length: 2 }, () => ({ operationAt: '2026-08-20T00:00:00+03:00', amountSigned: 100, commission: 0, description: 'Пополнение' })),
+};
+
 async function run(): Promise<void> {
   try {
     await importStatement(makeStatement(['first', 'first-second']));
@@ -18,11 +24,21 @@ async function run(): Promise<void> {
     await importStatement(makeStatement(['second']));
     const result = await pool.query('SELECT account_type, status FROM accounts WHERE id = $1', [account.rows[0].id]);
     assert.deepEqual(result.rows[0], { account_type: 'savings', status: 'closed' });
+    const duplicateResult = await importStatement(duplicateStatement);
+    if ('status' in duplicateResult) throw new Error(duplicateResult.message);
+    assert.deepEqual(duplicateResult, {
+      accountId: duplicateResult.accountId,
+      isNewAccount: true,
+      accountNumberMasked: 'fingerp******test',
+      imported: 2,
+      duplicatesSkipped: 0,
+      totalInFile: 2,
+    });
     console.log('import metadata SQL: OK');
   } finally {
-    await pool.query('DELETE FROM transactions WHERE account_id IN (SELECT id FROM accounts WHERE bank = \'TEST\' AND account_number = \'metadata-test\')');
-    await pool.query("DELETE FROM imports WHERE account_id IN (SELECT id FROM accounts WHERE bank = 'TEST' AND account_number = 'metadata-test')");
-    await pool.query("DELETE FROM accounts WHERE bank = 'TEST' AND account_number = 'metadata-test'");
+    await pool.query("DELETE FROM transactions WHERE account_id IN (SELECT id FROM accounts WHERE bank = 'TEST' AND account_number IN ('metadata-test', 'fingerprint-test'))");
+    await pool.query("DELETE FROM imports WHERE account_id IN (SELECT id FROM accounts WHERE bank = 'TEST' AND account_number IN ('metadata-test', 'fingerprint-test'))");
+    await pool.query("DELETE FROM accounts WHERE bank = 'TEST' AND account_number IN ('metadata-test', 'fingerprint-test')");
     await pool.end();
   }
 }

backend/src/services/import.test.ts

@@ -1,10 +1,12 @@
 import assert from 'node:assert/strict';
-import { determineDirection } from './import';
+import { computeFingerprint, determineDirection } from './import';
 
 assert.equal(determineDirection(1, 'Перечисление средств на счет N 123 со счета N 456'), 'transfer');
 assert.equal(determineDirection(1, 'Перечисление средств на вклад N 123'), 'transfer');
 assert.equal(determineDirection(-1, 'Перечисление суммы вклада при закрытии'), 'transfer');
 assert.equal(determineDirection(-1, 'Оплата покупки'), 'expense');
 assert.equal(determineDirection(1, 'Выплата процентов'), 'income');
+const duplicateTransaction = { operationAt: '2026-08-20T00:00:00+03:00', amountSigned: 100, commission: 0, description: 'Пополнение' };
+assert.notEqual(computeFingerprint('fingerprint-test', duplicateTransaction, 0), computeFingerprint('fingerprint-test', duplicateTransaction, 1));
 
 console.log('import direction: OK');

backend/src/services/import.ts

@@ -14,9 +14,10 @@ const TRANSFER_PHRASES = [
 const CASHBACK_KEYWORD = 'зачисление';
 const UUID_RE = /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;
 
-function computeFingerprint(
+export function computeFingerprint(
   accountNumber: string,
   tx: { operationAt: string; amountSigned: number; commission: number; description: string; sourceId?: string },
+  sourcePosition?: number,
 ): string {
   if (tx.sourceId) {
     const raw = [accountNumber, tx.sourceId.trim()].join('|');
@@ -29,6 +30,7 @@ function computeFingerprint(
     String(tx.amountSigned),
     String(tx.commission),
     tx.description.trim(),
+    ...(sourcePosition === undefined ? [] : [String(sourcePosition)]),
   ].join('|');
   const hash = crypto.createHash('sha256').update(raw, 'utf-8').digest('hex');
   return `sha256:${hash}`;
@@ -139,7 +141,7 @@ function validateSemantics(data: StatementFile): ValidationError | null {
   const operationIds = new Set<string>();
   for (let i = 0; i < data.transactions.length; i++) {
     const fp = computeFingerprint(data.statement.accountNumber, data.transactions[i]);
-    if (fps.has(fp)) {
+    if (data.transactions[i].sourceId && fps.has(fp)) {
       return { status: 422, error: 'VALIDATION_ERROR', message: `Duplicate fingerprint found within file at transaction index ${i}` };
     }
     fps.add(fp);
@@ -165,6 +167,15 @@ export async function importStatement(
   const data = body as StatementFile;
   const semErr = validateSemantics(data);
   if (semErr) return semErr;
+  const fallbackFingerprints = new Set<string>();
+  const duplicateFallbackFingerprints = new Set<string>();
+  for (const tx of data.transactions) {
+    if (!tx.sourceId) {
+      const fp = computeFingerprint(data.statement.accountNumber, tx);
+      if (fallbackFingerprints.has(fp)) duplicateFallbackFingerprints.add(fp);
+      fallbackFingerprints.add(fp);
+    }
+  }
 
   const client = await db.connect();
   try {
@@ -223,7 +234,10 @@ export async function importStatement(
     const insertedIds: number[] = [];
 
     for (const [sourcePosition, tx] of data.transactions.entries()) {
-      const fp = computeFingerprint(data.statement.accountNumber, tx);
+      const fallbackFingerprint = computeFingerprint(data.statement.accountNumber, tx);
+      const fp = !tx.sourceId && duplicateFallbackFingerprints.has(fallbackFingerprint)
+        ? computeFingerprint(data.statement.accountNumber, tx, sourcePosition)
+        : fallbackFingerprint;
       const isCashbackCommissionImport =
         tx.amountSigned === 0 &&
         tx.commission > 0 &&