From fd312032a4188ddfd658355933169dafc8406f87 Mon Sep 17 00:00:00 2001
From: Alex Gleason <alex@alexgleason.me>
Date: Sat, 25 Jan 2025 15:31:49 -0600
Subject: [PATCH] MultiRateLimiter: ensure the active limiter is used for
 ratelimit values

---
 src/utils/ratelimiter/MultiRateLimiter.test.ts |  2 ++
 src/utils/ratelimiter/MultiRateLimiter.ts      | 14 ++++++++++----
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/utils/ratelimiter/MultiRateLimiter.test.ts b/src/utils/ratelimiter/MultiRateLimiter.test.ts
index 3cfa4696..9b1fd648 100644
--- a/src/utils/ratelimiter/MultiRateLimiter.test.ts
+++ b/src/utils/ratelimiter/MultiRateLimiter.test.ts
@@ -34,6 +34,8 @@ Deno.test('MultiRateLimiter', async (t) => {
   });
 
   await t.step('throws when hit if second limit exceeded', () => {
+    assertEquals(limiter.client('test').limiter, limiter1);
     assertThrows(() => limiter.client('test').hit(), Error);
+    assertEquals(limiter.client('test').limiter, limiter2);
   });
 });
diff --git a/src/utils/ratelimiter/MultiRateLimiter.ts b/src/utils/ratelimiter/MultiRateLimiter.ts
index dc9b62a7..14b23142 100644
--- a/src/utils/ratelimiter/MultiRateLimiter.ts
+++ b/src/utils/ratelimiter/MultiRateLimiter.ts
@@ -3,7 +3,7 @@ import { RateLimiter, RateLimiterClient } from './types.ts';
 export class MultiRateLimiter {
   constructor(private limiters: RateLimiter[]) {}
 
-  client(key: string): RateLimiterClient {
+  client(key: string): MultiRateLimiterClient {
     return new MultiRateLimiterClient(key, this.limiters);
   }
 }
@@ -15,16 +15,22 @@ class MultiRateLimiterClient implements RateLimiterClient {
     }
   }
 
+  /** Returns the _active_ limiter, which is either the first exceeded or the first. */
+  get limiter(): RateLimiter {
+    const exceeded = this.limiters.find((limiter) => limiter.client(this.key).remaining < 0);
+    return exceeded ?? this.limiters[0];
+  }
+
   get hits(): number {
-    return this.limiters[0].client(this.key).hits;
+    return this.limiter.client(this.key).hits;
   }
 
   get resetAt(): Date {
-    return this.limiters[0].client(this.key).resetAt;
+    return this.limiter.client(this.key).resetAt;
   }
 
   get remaining(): number {
-    return this.limiters[0].client(this.key).remaining;
+    return this.limiter.client(this.key).remaining;
   }
 
   hit(n?: number): void {