Check if signature exists before writing to DB

src/app/api/flux/route.ts

@@ -56,7 +56,7 @@ export async function POST(req: NextRequest): Promise<NextResponse> {
       )
     }
 
-    await markSignatureAsUsed(transactionSignature)
+    await markSignatureAsUsed(transactionSignature);
 
     console.log('Generating with Flux model:', modelId)
     console.log('Prompt:', prompt)

src/data-source.ts

@@ -1,4 +1,5 @@
 import { DataSource } from 'typeorm';
+
 import { Payment } from './entity/Payment';
 
 export const AppDataSource = new DataSource({

src/utils/verifyPayment.ts

@@ -3,6 +3,7 @@ import { TOKEN_PROGRAM_ID } from '@solana/spl-token';
 
 import { AppDataSource } from '../data-source';
 import { Payment } from '../entity/Payment';
+import { getManager } from 'typeorm';
 
 const SOLANA_RPC_URL = process.env.NEXT_PUBLIC_SOLANA_RPC_URL;
 const SOLANA_WEBSOCKET_URL = process.env.NEXT_PUBLIC_SOLANA_WEBSOCKET_URL;
@@ -26,10 +27,18 @@ export async function isSignatureUsed(transactionSignature: string): Promise<boo
 }
 
 export async function markSignatureAsUsed(transactionSignature: string): Promise<void> {
-  const paymentRepository = AppDataSource.getRepository(Payment);
-  const payment = new Payment();
-  payment.transactionSignature = transactionSignature;
-  await paymentRepository.save(payment);
+  await AppDataSource.transaction(async (transactionalEntityManager) => {
+    const paymentRepository = transactionalEntityManager.getRepository(Payment);
+
+    // Check if the payment with the given signature already exists
+    const exists = await paymentRepository.exists({ where: { transactionSignature } });
+
+    // If not, create a new payment entry
+    if (!exists) {
+      const newPayment = paymentRepository.create({ transactionSignature });
+      await paymentRepository.save(newPayment);
+    }
+  });
 }
 
 export async function verifyPayment(