ACP Checkout: Webhooks, Idempotency, and Going Live

// Stripe webhook handler
app.post('/webhooks/stripe', express.raw({ type: 'application/json' }), async (req, res) => {
  const sig = req.headers['stripe-signature']
  const event = stripe.webhooks.constructEvent(req.body, sig, process.env.STRIPE_WEBHOOK_SECRET)

  switch (event.type) {
    case 'payment_intent.succeeded':
      await fulfillOrder(event.data.object.metadata.order_id)
      break
    case 'payment_intent.payment_failed':
      await markOrderFailed(event.data.object.metadata.order_id)
      break
  }

  res.json({ received: true })
})

// Middleware to handle idempotency
async function idempotencyMiddleware(req, res, next) {
  const key = req.headers['idempotency-key'] || req.body.idempotency_key

  if (!key) return next() // not required on updates

  const cached = await redis.get(`idem:${key}`)
  if (cached) {
    return res.json(JSON.parse(cached)) // return cached response
  }

  // Capture response before sending
  const originalJson = res.json.bind(res)
  res.json = (body) => {
    redis.setex(`idem:${key}`, 3600, JSON.stringify(body)) // cache for 1 hour
    return originalJson(body)
  }

  next()
}

app.post('/acp/checkout/complete', idempotencyMiddleware, async (req, res) => {
  // ... complete checkout
})