2 files changed, 45 insertions, 24 deletions
diff --git a/lib/db.js b/lib/db.js
index b22af94a..197697a0 100644
--- a/lib/db.js
+++ b/lib/db.js
@@ -1,9 +1,42 @@
 import config from "$config";
 import { sleep } from "$lib/utils";
-import { createClient } from "redis";
+import { createClient, defineScript } from "redis";
 import { warn } from "$lib/logging";
 
-export const db = createClient({ url: config.db });
+let SCRIPT = `
+local balanceKey = KEYS[1]
+local creditKey = KEYS[2]
+local amount = tonumber(ARGV[1])
+local tip = tonumber(ARGV[2])
+local fee = tonumber(ARGV[3])
+local ourfee = tonumber(ARGV[4])
+
+local balance = tonumber(redis.call('get', balanceKey) or '0')
+local credit = tonumber(redis.call('get', creditKey) or '0')
+
+local covered = math.min(credit, ourfee)
+ourfee = ourfee - covered
+
+if balance < amount + tip + fee + ourfee then
+    return {err = 'Insufficient funds'}
+end
+
+redis.call('decrby', creditKey, tostring(math.floor(covered)))
+redis.call('decrby', balanceKey, tostring(math.floor(amount + tip + fee + ourfee)))
+
+return {ok = 'ok'}
+`;
+
+let debit = defineScript({
+  NUMBER_OF_KEYS: 2,
+  SCRIPT,
+  transformArguments: (...args) => args.map(a => a.toString())
+});
+
+export const db = createClient({
+  url: config.db,
+  scripts: { debit }
+});
 await db.connect();
 export default db;
 
diff --git a/lib/payments.js b/lib/payments.js
index e1ed5d0b..f39e2937 100644
--- a/lib/payments.js
+++ b/lib/payments.js
@@ -63,29 +63,17 @@ export let debit = async (
     ? Math.round(amount * config.fee)
     : 0;
 
-  await t(`balance:${uid}`, async (balance, db) => {
-    await t(`credit:${type}:${uid}`, async (credit, db) => {
-      let covered = Math.min(credit, ourfee) || 0;
-      ourfee -= covered;
+  let r = await db.debit(
+    `balance:${uid}`,
+    `credit:${type}:${uid}`,
+    amount || 0,
+    tip || 0,
+    fee || 0,
+    ourfee || 0
+  );
+
 
-      l(
-        "debiting",
-        user.username,
-        balance,
-        amount,
-        tip,
-        fee,
-        ourfee,
-        amount + fee + ourfee + tip
-      );
-      if (balance < amount + tip + fee + ourfee) fail("Insufficient funds");
-      await db
-        .multi()
-        .decrBy(`credit:${type}:${uid}`, covered)
-        .decrBy(`balance:${uid}`, amount + tip + fee + ourfee)
-        .exec();
-    });
-  });
+  if (r !== "ok") fail("Insufficient funds");
 
   let p = {
     id,