payment-gateway-expert · diff
v3.0.0 to v4.0.0
132 added, 130 removed. Audit A to A.
- ---
- name: payment-gateway-expert
- description: "Expert guide for integrating payment gateways (Stripe, PayPal, Xendit, Midtrans, DOKU) and secure webhooks into SaaS platforms / Panduan ahli integrasi payment gateway dan webhook aman."
- author: "Roedy Rustam"
- version: "3.0.0"
- ---
-
- # Payment Gateway Expert / Ahli Payment Gateway
-
- [English](#english) | [Bahasa Indonesia](#bahasa-indonesia)
-
- ---
-
- <a name="english"></a>
- ## English
-
- ### Description
- Expert guide for integrating major payment gateways (Stripe, PayPal, Xendit, Midtrans, DOKU) into modern SaaS platforms. Covers checkout flows, secure webhook handling, subscription management, and synchronization with local databases.
-
- ### Instructions
- - **Security First**: Always validate webhook signatures before processing any payment event. Never trust client-side data for prices or payment status. For DOKU, ensure signature components (like request target) are arranged strictly according to documentation.
- - **Idempotency**: Implement idempotency keys for all payment creation requests to avoid duplicate charges. Webhook handlers must also be idempotent. For DOKU, include a unique `Request-Id` header.
- - **State Synchronization**: Ensure the local database (e.g., PostgreSQL, Supabase) is updated immediately and transactionally upon receiving successful webhook events.
- - **Subscription Management**: Map the provider's subscription statuses (e.g., `active`, `past_due`, `canceled`) accurately to the SaaS platform's internal state machine.
- - **Testing**: Use sandbox/test environments provided by the gateways and simulate webhooks using CLI tools (like Stripe CLI) during development.
-
- ### Implementation Checklist
- - [ ] Create a dedicated Webhook endpoint (e.g., `/api/webhooks/stripe`).
- - [ ] Use raw request body for signature verification (do not parse JSON before verification).
- - [ ] Ensure idempotency by tracking processed event IDs in the database.
- - [ ] Update local user/subscription state transactionally upon success.
- - [ ] Handle asynchronous failures with a dead-letter queue or retry mechanism.
-
- ### Example: Stripe Webhook Signature Verification (Next.js App Router)
- ```typescript
- import Stripe from 'stripe';
- import { headers } from 'next/headers';
-
- const stripe = new Stripe(process.env.STRIPE_SECRET_KEY!);
-
- export async function POST(req: Request) {
- const body = await req.text(); // Raw body required for signature
- const signature = headers().get('Stripe-Signature') as string;
-
- let event: Stripe.Event;
-
- try {
- event = stripe.webhooks.constructEvent(
- body,
- signature,
- process.env.STRIPE_WEBHOOK_SECRET!
- );
- } catch (err: any) {
- return new Response(`Webhook Error: ${err.message}`, { status: 400 });
- }
-
- // Handle the event
- if (event.type === 'checkout.session.completed') {
- // Process successful payment, check idempotency, update DB
- }
-
- return new Response(JSON.stringify({ received: true }), { status: 200 });
- }
- ```
-
- ## Orchestration & Integration
- - Integrates with: `saas-billing`, `doku-payment-gateway`, `saas-mvp-launcher`.
-
- ### Trigger Conditions
- Active whenever the user is working on billing integration, payment checkout, webhook handling, or integrating platforms like PayPal, Stripe, Xendit, Midtrans, or DOKU.
-
- ---
-
- <a name="bahasa-indonesia"></a>
- ## Bahasa Indonesia
-
- ### Deskripsi
- Panduan ahli untuk mengintegrasikan payment gateway utama (Stripe, PayPal, Xendit, Midtrans, DOKU) ke platform SaaS modern. Mencakup alur checkout, penanganan webhook yang aman, manajemen langganan, dan sinkronisasi dengan database lokal.
-
- ### Instruksi
- - **Keamanan Utama**: Selalu validasi signature webhook sebelum memproses event pembayaran apa pun. Jangan pernah mempercayai data dari sisi klien untuk harga atau status pembayaran. Untuk DOKU, pastikan komponen signature (seperti request target) disusun secara ketat sesuai dokumentasi.
- - **Idempotensi**: Implementasikan kunci idempotensi (idempotency keys) untuk semua permintaan pembuatan pembayaran untuk menghindari tagihan ganda. Handler webhook juga harus idempoten. Untuk DOKU, sertakan header `Request-Id` unik.
- - **Sinkronisasi State**: Pastikan database lokal (misal: PostgreSQL, Supabase) diperbarui secara langsung dan transaksional saat menerima event webhook yang berhasil.
- - **Manajemen Langganan**: Petakan status langganan dari provider (misal: `active`, `past_due`, `canceled`) secara akurat ke state machine internal platform SaaS.
- - **Pengujian**: Gunakan lingkungan sandbox/test yang disediakan oleh gateway dan simulasikan webhook menggunakan tool CLI (seperti Stripe CLI) selama pengembangan.
-
- ### Checklist Implementasi
- - [ ] Buat endpoint Webhook khusus (misal: `/api/webhooks/stripe`).
- - [ ] Gunakan raw request body untuk verifikasi signature (jangan parse JSON sebelum verifikasi).
- - [ ] Pastikan idempotensi dengan melacak ID event yang sudah diproses di database.
- - [ ] Perbarui state langganan/pengguna lokal secara transaksional saat sukses.
- - [ ] Tangani kegagalan asinkron dengan dead-letter queue atau mekanisme retry.
-
- ### Contoh: Verifikasi Signature Webhook Stripe (Next.js App Router)
- ```typescript
- import Stripe from 'stripe';
- import { headers } from 'next/headers';
-
- const stripe = new Stripe(process.env.STRIPE_SECRET_KEY!);
-
- export async function POST(req: Request) {
- const body = await req.text(); // Raw body dibutuhkan untuk signature
- const signature = headers().get('Stripe-Signature') as string;
-
- let event: Stripe.Event;
-
- try {
- event = stripe.webhooks.constructEvent(
- body,
- signature,
- process.env.STRIPE_WEBHOOK_SECRET!
- );
- } catch (err: any) {
- return new Response(`Webhook Error: ${err.message}`, { status: 400 });
- }
-
- // Tangani event
- if (event.type === 'checkout.session.completed') {
- // Proses pembayaran sukses, cek idempotensi, update DB
- }
-
- return new Response(JSON.stringify({ received: true }), { status: 200 });
- }
- ```
-
- ## Integrasi Orkestrasi
- - Terintegrasi dengan: `saas-billing`, `doku-payment-gateway`, `saas-mvp-launcher`.
-
- ### Kondisi Pemicu
- Aktif setiap kali pengguna sedang mengerjakan integrasi billing, checkout pembayaran, penanganan webhook, atau mengintegrasikan platform seperti PayPal, Stripe, Xendit, Midtrans, atau DOKU.
+ ---
+ name: payment-gateway-expert
+ description: "Expert guide for integrating payment gateways (Stripe, PayPal, Xendit, Midtrans, DOKU SNAP BI) and secure webhooks into SaaS platforms / Panduan ahli integrasi payment gateway dan webhook aman."
+ author: "Roedy Rustam"
+ version: "4.0.0"
+ ---
+
+ # Payment Gateway Expert / Ahli Payment Gateway
+
+ [English](#english) | [Bahasa Indonesia](#bahasa-indonesia)
+
+ ---
+
+ <a name="english"></a>
+ ## English
+
+ ### Description
+ Expert guide for integrating major payment gateways (Stripe, PayPal, Xendit, Midtrans, DOKU SNAP BI) into modern SaaS platforms. Covers checkout flows, secure raw-body webhook handling, atomic idempotency to prevent race conditions, subscription state machines, and local database synchronization.
+
+ ### Core Principles
+ - **Security First**: Always validate webhook signatures using the raw, unparsed request body before processing any payment event. Never trust client-side data for prices or payment status. For Indonesian gateways (DOKU, Midtrans, Xendit), strictly enforce the **SNAP BI standard (HMAC-SHA512)** and ISO8601 UTC/WIB timestamps.
+ - **Idempotency & Race Condition Prevention**: Implement idempotency keys for all payment creation requests. For webhook ingestion, **DO NOT rely solely on `findUnique` checks**, as concurrent webhook retries cause race conditions. Always use **Atomic Updates** (`UPDATE ... WHERE status = 'PENDING'`) or database pessimistic locks (`SELECT ... FOR UPDATE`).
+ - **Raw Body Ingestion**: Webhook signature verification fails if JSON is parsed or re-serialized with modified key ordering. Extract the exact raw string buffer (`req.text()` in Fetch API or `express.raw({ type: 'application/json' })` in Express).
+ - **Early 200 OK Acknowledgment**: If a webhook event is verified but already processed, immediately return `200 OK` so the payment gateway halts retries.
+ - **State Synchronization**: Ensure the local database (e.g., PostgreSQL, Supabase via Drizzle/Prisma) is updated transactionally upon receiving successful webhook events.
+ - **Subscription Management**: Map provider subscription statuses (`trialing`, `active`, `past_due`, `canceled`) accurately to internal SaaS state machines.
+
+ ### Implementation Checklist
+ - [ ] Create dedicated raw Webhook endpoint (e.g., `/api/webhooks/stripe`, `/api/webhooks/doku`).
+ - [ ] Use raw request body string for signature verification (never parsed JSON).
+ - [ ] Verify signature using proper algorithm (HMAC-SHA256 for Stripe/PayPal; HMAC-SHA512 for SNAP BI).
+ - [ ] Implement Atomic Update idempotency (`WHERE status = 'PENDING'`) to eliminate race conditions.
+ - [ ] Acknowledge duplicate webhooks immediately with HTTP `200 OK`.
+ - [ ] Offload heavy post-payment operations (invoicing, emails, webhooks) to background job queues (BullMQ/Temporal).
+
+ ### Example: SNAP BI Webhook & Atomic Idempotency (Next.js App Router)
+ ```typescript
+ import { headers } from 'next/headers';
+ import crypto from 'crypto';
+ import { db } from '@/lib/db';
+
+ export async function POST(req: Request) {
+ const rawBody = await req.text(); // Raw body is mandatory
+ const headerList = await headers();
+
+ const timestamp = headerList.get('x-timestamp') || '';
+ const receivedSig = headerList.get('x-signature') || '';
+ const authHeader = headerList.get('authorization') || '';
+ const token = authHeader.replace(/^Bearer\s+/i, '');
+ const path = new URL(req.url).pathname;
+
+ // 1. SNAP BI Body Hash & Signature Verification (HMAC-SHA512)
+ const bodyHash = crypto.createHash('sha256').update(rawBody, 'utf8').digest('hex').toLowerCase();
+ const stringToSign = `POST:${path}:${token}:${bodyHash}:${timestamp}`;
+ const calculatedSig = crypto
+ .createHmac('sha512', process.env.DOKU_SECRET_KEY!)
+ .update(stringToSign, 'utf8')
+ .digest('base64');
+
+ const isValid = crypto.timingSafeEqual(Buffer.from(receivedSig), Buffer.from(calculatedSig));
+ if (!isValid) {
+ return new Response('Invalid Signature', { status: 401 });
+ }
+
+ const payload = JSON.parse(rawBody);
+ const invoiceNumber = payload.order?.invoice_number;
+
+ // 2. Atomic Update: Eliminates Race Conditions by locking on 'PENDING' status
+ const updated = await db.transaction.updateMany({
+ where: {
+ invoiceNumber: invoiceNumber,
+ status: 'PENDING', // Key race condition prevention gate
+ },
+ data: {
+ status: 'PAID',
+ paidAt: new Date(),
+ externalReference: payload.transaction?.original_reference_no,
+ },
+ });
+
+ // 3. Duplicate Webhook Handling (Idempotency)
+ if (updated.count === 0) {
+ // Already processed or invalid invoice — return 200 to halt gateway retry spam
+ return new Response(JSON.stringify({ status: 'ALREADY_PROCESSED' }), { status: 200 });
+ }
+
+ // 4. Fulfillment (Execute only once)
+ await grantUserSubscription(invoiceNumber);
+
+ return new Response(JSON.stringify({ status: 'SUCCESS' }), { status: 200 });
+ }
+
+ async function grantUserSubscription(invoiceNumber: string) {
+ // Safe business logic execution
+ }
+ ```
+
+ ## Orchestration & Integration
+ - Integrates with: `saas-billing`, `doku-payment-gateway`, `doku-mcp-server`, `async-queue-temporal-expert`, `database-orm-expert`.
+
+ ### Trigger Conditions
+ Active whenever the user is working on billing integration, payment checkout, webhook handling, or integrating platforms like PayPal, Stripe, Xendit, Midtrans, or DOKU SNAP BI.
+
+ ---
+
+ <a name="bahasa-indonesia"></a>
+ ## Bahasa Indonesia
+
+ ### Deskripsi
+ Panduan ahli untuk mengintegrasikan payment gateway utama (Stripe, PayPal, Xendit, Midtrans, DOKU SNAP BI) ke platform SaaS modern. Mencakup alur checkout, penanganan webhook raw-body aman, pencegahan race condition melalui atomic update, state machine langganan, dan sinkronisasi database lokal.
+
+ ### Prinsip Utama
+ - **Keamanan Utama**: Selalu validasi signature webhook menggunakan *raw request body* murni sebelum memproses event pembayaran. Jangan pernah mempercayai data dari sisi klien untuk harga atau status pembayaran. Untuk gateway Indonesia (DOKU, Midtrans, Xendit), terapkan **standar SNAP BI (HMAC-SHA512)** dan format timestamp ISO8601.
+ - **Idempotensi & Pencegahan Race Condition**: Implementasikan kunci idempotensi untuk semua pembuatan pembayaran. Pada penerimaan webhook, **JANGAN hanya mengandalkan pengecekan `findUnique`**, karena panggilan webhook paralel dari gateway dapat memicu race condition. Selalu gunakan **Atomic Update** (`UPDATE ... WHERE status = 'PENDING'`) atau database lock (`SELECT ... FOR UPDATE`).
+ - **Raw Body Webhook**: Verifikasi tanda tangan akan gagal jika JSON di-parse atau di-serialize ulang karena perubahan urutan key atau spasi. Ambil buffer teks mentah (`req.text()` pada Fetch API atau `express.raw({ type: 'application/json' })` di Express).
+ - **Balasan Cepat 200 OK**: Jika signature valid namun transaksi sudah berstatus lunas (webhook duplikat/retry), segera kembalikan HTTP `200 OK` agar payment gateway berhenti mengirimkan retry.
+ - **Sinkronisasi State**: Pastikan database lokal (PostgreSQL/Supabase via Drizzle/Prisma) diperbarui secara transaksional saat menerima webhook sukses.
+ - **Manajemen Langganan**: Petakan status langganan dari provider (`trialing`, `active`, `past_due`, `canceled`) secara akurat ke state machine internal SaaS.
+
+ ### Checklist Implementasi
+ - [ ] Buat endpoint Webhook raw khusus (misal: `/api/webhooks/stripe`, `/api/webhooks/doku`).
+ - [ ] Gunakan raw request body string untuk verifikasi signature (jangan parse JSON sebelum verifikasi).
+ - [ ] Verifikasi signature dengan algoritma yang tepat (HMAC-SHA256 untuk Stripe/PayPal; HMAC-SHA512 untuk SNAP BI).
+ - [ ] Terapkan Atomic Update (`WHERE status = 'PENDING'`) untuk mematikan peluang race condition.
+ - [ ] Balas webhook duplikat secara instan dengan HTTP `200 OK`.
+ - [ ] Lemparkan proses berat pasca-bayar (pembuatan invoice PDF, email, push notification) ke antrean latar belakang (BullMQ/Temporal).
+
+ ## Integrasi Orkestrasi
+ - Terintegrasi dengan: `saas-billing`, `doku-payment-gateway`, `doku-mcp-server`, `async-queue-temporal-expert`, `database-orm-expert`.
+
+ ### Kondisi Pemicu
+ Aktif setiap kali pengguna sedang mengerjakan integrasi billing, checkout pembayaran, penanganan webhook, atau mengintegrasikan platform seperti PayPal, Stripe, Xendit, Midtrans, atau DOKU SNAP BI.