From 37cc5f16def3a804ad973162166ec578bc715383 Mon Sep 17 00:00:00 2001
From: shiftinv <me@shiftinv.cc>
Date: Sat, 3 Sep 2022 18:03:51 +0200
Subject: [PATCH] feat: handle ratelimits (kinda)

---
 lib/config.ts  |  2 ++
 lib/handler.ts | 38 +++++++++++++++++++++++++++++++-------
 lib/util.ts    |  4 ++++
 3 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/lib/config.ts b/lib/config.ts
index d8e4e48..9249e33 100644
--- a/lib/config.ts
+++ b/lib/config.ts
@@ -13,4 +13,6 @@ export default {
     hostname: get("HOSTNAME", "127.0.0.1"),
     port: parseInt(get("PORT", "8080")),
     signKey: get("SIGN_KEY"),
+    maxWebhookRetries: parseInt(get("MAX_RETRIES", "3")),
+    maxWebhookRetryMs: parseInt(get("MAX_RETRY_MS", "30000")),
 };
diff --git a/lib/handler.ts b/lib/handler.ts
index 783308f..9850601 100644
--- a/lib/handler.ts
+++ b/lib/handler.ts
@@ -1,4 +1,5 @@
 import { http, log } from "../deps.ts";
+import config from "./config.ts";
 import { verify } from "./crypto.ts";
 import filterWebhook from "./filter.ts";
 import { UrlConfig } from "./types.d.ts";
@@ -65,11 +66,34 @@ async function sendWebhook(
     body: string,
 ): Promise<Response> {
     const url = `https://discord.com/api/webhooks/${id}/${token}/github?wait=1`;
-    log.info(`Sending webhook request to ${url}`);
-    const req = new Request(url, {
-        method: "POST",
-        headers: headers,
-        body: body,
-    });
-    return await fetch(req);
+
+    let res: Response;
+    let retries = 0;
+    do {
+        const req = new Request(url, {
+            method: "POST",
+            headers: headers,
+            body: body,
+        });
+
+        log.info(`sending webhook request to ${url}`);
+        res = await fetch(req);
+
+        // return response if everything's fine
+        if (res.status !== 429) break;
+
+        const reset = res.headers.get("retry-after");
+        // should always exist, even for cf bans, but checking anyway
+        if (reset === null) break;
+
+        const resetms = parseFloat(reset);
+        // if we'd wait longer than the configured limit, just return the 429
+        if (resetms > config.maxWebhookRetryMs) break;
+
+        // wait and try again
+        log.warning(`retrying after ${resetms}ms`);
+        await util.sleep(resetms);
+        retries++;
+    } while (retries <= config.maxWebhookRetries);
+    return res;
 }
diff --git a/lib/util.ts b/lib/util.ts
index 7fc7393..d33510a 100644
--- a/lib/util.ts
+++ b/lib/util.ts
@@ -1,3 +1,7 @@
 export function parseBool(s: string): boolean {
     return ["1", "true", "on", "y", "yes"].includes(s.toLowerCase());
 }
+
+export function sleep(ms: number): Promise<void> {
+    return new Promise((resolve) => setTimeout(resolve, ms));
+}