Let provider events move the order

How to do it

The rule confirm payments on the server explains why the success page proves nothing. Verify each event as in signed webhooks. Handle duplicates as in idempotent receivers, and expect any order, as in event order. Keep one table from event type to transition. Before acting, read the payment from the provider's API and compare amount, currency and order ID with the order. Answer 2xx within 5 seconds and queue the work. Log event types you do not handle, and ignore them.

Example

const EVENT_TRANSITIONS = {
  'payment_intent.processing': 'processing',
  'payment_intent.succeeded': 'paid',
  'payment_intent.payment_failed': 'payment_failed',
}

async function onPaymentEvent(event) {
  const to = EVENT_TRANSITIONS[event.type]
  if (!to) return logIgnoredEvent(event.type)
  const payment = await stripe.paymentIntents.retrieve(event.data.object.id)
  const order = await orders.get(payment.metadata.orderId)
  if (payment.amount !== order.totalMinor || payment.currency !== order.currency.toLowerCase()) {
    throw new Error(`Payment ${payment.id} does not match order ${order.id}`)
  }
  await moveOrder(db, order.id, order.state, to, event.id)
}

EVENT_TRANSITIONS = {
    "payment_intent.processing": "processing",
    "payment_intent.succeeded": "paid",
    "payment_intent.payment_failed": "payment_failed",
}

def on_payment_event(event) -> None:
    to_state = EVENT_TRANSITIONS.get(event["type"])
    if to_state is None:
        return log_ignored_event(event["type"])
    payment = stripe.PaymentIntent.retrieve(event["data"]["object"]["id"])
    order = orders.get(payment.metadata["order_id"])
    if payment.amount != order.total_minor or payment.currency != order.currency.lower():
        raise PaymentMismatch(payment.id, order.id)
    move_order(db, order.id, order.state, to_state, event["id"])

How to check

Send a signed test event for a payment whose amount differs from the order. The handler refuses to mark the order paid. Every event type enabled on the webhook endpoint appears in the mapping table or in an explicit ignore list.