Webhook Discord

server/lib/billing.js

@@ -400,6 +400,20 @@ const writeIdempotentValue = async (db, key, value) => {
   );
 };
 
+// Atomically claims a one-time slot for the given key (e.g. per webhook event
+// notification). Returns true only for the first caller; concurrent retries of
+// the same event lose the INSERT race and get false.
+const claimNotificationOnce = async (db, key) => {
+  const result = await run(
+    db,
+    `INSERT INTO billing_idempotency (id, response_json, created_at)
+     VALUES ($1, CAST($2 AS jsonb), $3)
+     ON CONFLICT (id) DO NOTHING`,
+    [key, JSON.stringify({ claimedAt: nowIso() }), nowIso()],
+  );
+  return result.changes > 0;
+};
+
 const grantRevenueCatTopupIfNeeded = async (db, account, transactionId, productId) => {
   if (!transactionId || !isSupportedTopupProduct(productId)) {
     return false;
@@ -790,6 +804,7 @@ const isInsufficientCreditsError = (error) => {
 module.exports = {
   AVAILABLE_PRODUCTS,
   chargeKey,
+  claimNotificationOnce,
   consumeCreditsWithIdempotency,
   endpointKey,
   ensureBillingSchema,