feat: @discordjs/proxy (#7925)

Co-authored-by: Parbez <imranbarbhuiya.fsd@gmail.com>

packages/proxy/src/util/responseHelpers.ts

@@ -0,0 +1,54 @@
+import type { ServerResponse } from 'node:http';
+import { pipeline } from 'node:stream/promises';
+import type { DiscordAPIError, HTTPError, RateLimitError } from '@discordjs/rest';
+import type { Dispatcher } from 'undici';
+
+/**
+ * Populates a server response with the data from a Discord 2xx REST response
+ * @param res The server response to populate
+ * @param data The data to populate the response with
+ */
+export async function populateSuccessfulResponse(res: ServerResponse, data: Dispatcher.ResponseData): Promise<void> {
+	res.statusCode = data.statusCode;
+
+	for (const header of Object.keys(data.headers)) {
+		// Strip ratelimit headers
+		if (header.startsWith('x-ratelimit')) {
+			continue;
+		}
+
+		res.setHeader(header, data.headers[header]!);
+	}
+
+	await pipeline(data.body, res);
+}
+
+/**
+ * Populates a server response with the data from a Discord non-2xx REST response that is NOT a 429
+ * @param res The server response to populate
+ * @param error The error to populate the response with
+ */
+export function populateGeneralErrorResponse(res: ServerResponse, error: DiscordAPIError | HTTPError): void {
+	res.statusCode = error.status;
+	res.statusMessage = error.message;
+
+	if ('rawError' in error) {
+		res.setHeader('Content-Type', 'application/json');
+		res.write(JSON.stringify(error.rawError));
+	}
+}
+
+/**
+ * Populates a server response with the data from a Discord 429 REST response
+ * @param res The server response to populate
+ * @param error The error to populate the response with
+ */
+export function populateRatelimitErrorResponse(res: ServerResponse, error: RateLimitError): void {
+	res.statusCode = 429;
+	res.setHeader('Retry-After', error.timeToReset / 1000);
+}
+
+export function populateAbortErrorResponse(res: ServerResponse): void {
+	res.statusCode = 504;
+	res.statusMessage = 'Upstream timed out';
+}

packages/proxy/src/util/util.ts

@@ -0,0 +1,10 @@
+import type { IncomingMessage, ServerResponse } from 'node:http';
+
+/**
+ * Represents a potentially awaitable value
+ */
+export type Awaitable<T> = T | PromiseLike<T>;
+/**
+ * Represents a simple HTTP request handler
+ */
+export type RequestHandler = (req: IncomingMessage, res: ServerResponse) => Awaitable<void>;