From 27cd12553287385b8bdc70e5e86f0afbdb981522 Mon Sep 17 00:00:00 2001
From: gauthier-th <mail@gauthierth.fr>
Date: Wed, 26 Jun 2024 14:55:47 +0200
Subject: [PATCH] refactor: add rate limit to fetch api

---
 server/utils/rateLimit.ts | 61 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 server/utils/rateLimit.ts

diff --git a/server/utils/rateLimit.ts b/server/utils/rateLimit.ts
new file mode 100644
index 00000000..6049037e
--- /dev/null
+++ b/server/utils/rateLimit.ts
@@ -0,0 +1,61 @@
+export type RateLimitOptions = {
+  maxRequests?: number;
+  perMilliseconds?: number;
+  maxRPS?: number;
+};
+
+export default function rateLimit<
+  T extends (...args: Parameters<T>) => Promise<U>,
+  U
+>(fn: T, options: RateLimitOptions): (...args: Parameters<T>) => Promise<U> {
+  const maxRequests = options.maxRPS ?? options.maxRequests ?? 1;
+  const perMilliseconds = options.maxRPS
+    ? 1000
+    : options.perMilliseconds ?? 1000;
+
+  const queue: {
+    args: Parameters<T>;
+    resolve: (value: U) => void;
+  }[] = [];
+  let activeRequests = 0;
+  let timer: NodeJS.Timeout | null = null;
+
+  const processQueue = () => {
+    if (queue.length === 0) {
+      if (timer) {
+        clearInterval(timer);
+        timer = null;
+      }
+      return;
+    }
+
+    while (activeRequests < maxRequests) {
+      activeRequests++;
+      const item = queue.shift();
+      if (!item) break;
+      const { args, resolve } = item;
+      fn(...args)
+        .then(resolve)
+        .finally(() => {
+          activeRequests--;
+          if (queue.length > 0) {
+            if (!timer) {
+              timer = setInterval(processQueue, perMilliseconds);
+            }
+          } else {
+            if (timer) {
+              clearInterval(timer);
+              timer = null;
+            }
+          }
+        });
+    }
+  };
+
+  return (...args: Parameters<T>): Promise<U> => {
+    return new Promise<U>((resolve) => {
+      queue.push({ args, resolve });
+      processQueue();
+    });
+  };
+}