feat: add trailing backticks if description length exceeds discord limit

lib/formatter.ts

@@ -0,0 +1,34 @@
+// Empirically determined GitHub embed description limit in the Discord API.
+// Anything above this will be ellipsized :/
+const EMBED_LIMIT = 500;
+
+function maybeTransformText(s: string): string {
+    // If length exceeds limit, add backticks since they might otherwise be removed
+    const suffix = "…\n```";
+    const maxLen = EMBED_LIMIT - suffix.length;
+    if (s.includes("```") && s.length > maxLen) {
+        s = s.substring(0, maxLen) + suffix;
+    }
+    return s;
+}
+
+export default function fixupEmbeds(data: Record<string, any>): void {
+    for (
+        const field of [
+            // issue
+            "issue",
+            // issue/pr/discussion comment
+            "comment",
+            // pr
+            "pull_request",
+            // pr review
+            "review",
+            // discussion
+            "discussion",
+            // discussion answer
+            "answer",
+        ]
+    ) {
+        if (data[field]?.body) data[field].body = maybeTransformText(data[field].body);
+    }
+}

lib/handler.ts

@@ -2,6 +2,7 @@ import { http } from "../deps.ts";
 import config from "./config.ts";
 import { hasKey, verify } from "./crypto.ts";
 import filterWebhook from "./filter.ts";
+import fixupEmbeds from "./formatter.ts";
 import { UrlConfig } from "./types.d.ts";
 import { parseBool, requestLog } from "./util.ts";
 import { sendWebhook } from "./webhook.ts";
@@ -37,7 +38,7 @@ export default async function handle(
     // extract data
     const urlConfig = getUrlConfig(url.searchParams);
     const data = await req.text();
-    const json = JSON.parse(data);
+    const json: Record<string, any> = JSON.parse(data);
 
     // do the thing
     const filterReason = await filterWebhook(req.headers, json, urlConfig);
@@ -47,7 +48,10 @@ export default async function handle(
         return new Response(`Ignored by webhook filter (reason: ${filterReason})`, { status: 203 });
     }
 
-    return await sendWebhook(id, token, req.headers, data);
+    // mutate `json` in-place (fixing codeblocks etc.)
+    fixupEmbeds(json);
+
+    return await sendWebhook(id, token, req.headers, json);
 }
 
 function getUrlConfig(params: URLSearchParams): UrlConfig {

lib/webhook.ts

@@ -5,10 +5,11 @@ export async function sendWebhook(
     id: string,
     token: string,
     headers: Headers,
-    body: string,
+    data: Record<string, any>,
 ): Promise<[Response, Record<string, string>]> {
     const reqLog = requestLog(headers);
     const url = `https://discord.com/api/webhooks/${id}/${token}/github?wait=1`;
+    const body = JSON.stringify(data);
 
     let res: Response;
     let retries = 0;