[https-proxy-agent] Emit "proxyConnect" event on HTTP req (#154)

Part of #153.

I'd like to also emit this event on the `agent` instance itself, but
this is currently blocked by
DefinitelyTyped/DefinitelyTyped#65408.

.changeset/blue-buses-build.md

@@ -0,0 +1,5 @@
+---
+'https-proxy-agent': minor
+---
+
+Emit "proxyConnect" event on HTTP `request` object (part of #153)

packages/https-proxy-agent/src/index.ts

@@ -5,7 +5,7 @@ import assert from 'assert';
 import createDebug from 'debug';
 import { OutgoingHttpHeaders } from 'http';
 import { Agent, AgentConnectOpts } from 'agent-base';
-import parseProxyResponse from './parse-proxy-response';
+import { parseProxyResponse } from './parse-proxy-response';
 
 const debug = createDebug('https-proxy-agent');
 
@@ -130,9 +130,10 @@ export class HttpsProxyAgent<Uri extends string> extends Agent {
 
 		socket.write(`${payload}\r\n`);
 
-		const { statusCode, buffered } = await proxyResponsePromise;
+		const { connect, buffered } = await proxyResponsePromise;
+		req.emit('proxyConnect', connect);
 
-		if (statusCode === 200) {
+		if (connect.statusCode === 200) {
 			req.once('socket', resume);
 
 			if (opts.secureEndpoint) {

packages/https-proxy-agent/src/parse-proxy-response.ts

@@ -1,16 +1,18 @@
 import createDebug from 'debug';
+import { IncomingHttpHeaders } from 'http';
 import { Readable } from 'stream';
 
 const debug = createDebug('https-proxy-agent:parse-proxy-response');
 
-export interface ProxyResponse {
+export interface ConnectResponse {
 	statusCode: number;
-	buffered: Buffer;
+	statusText: string;
+	headers: IncomingHttpHeaders;
 }
 
-export default function parseProxyResponse(
+export function parseProxyResponse(
 	socket: Readable
-): Promise<ProxyResponse> {
+): Promise<{ connect: ConnectResponse; buffered: Buffer }> {
 	return new Promise((resolve, reject) => {
 		// we need to buffer any HTTP traffic that happens with the proxy before we get
 		// the CONNECT response, so that if the response is anything other than an "200"
@@ -60,16 +62,40 @@ export default function parseProxyResponse(
 				return;
 			}
 
-			const firstLine = buffered.toString(
-				'ascii',
-				0,
-				buffered.indexOf('\r\n')
-			);
-			const statusCode = +firstLine.split(' ')[1];
+			const headerParts = buffered.toString('ascii').split('\r\n');
+			const firstLine = headerParts.shift();
+			if (!firstLine) {
+				throw new Error('No header received');
+			}
+			const firstLineParts = firstLine.split(' ');
+			const statusCode = +firstLineParts[1];
+			const statusText = firstLineParts.slice(2).join(' ');
+			const headers: IncomingHttpHeaders = {};
+			for (const header of headerParts) {
+				if (!header) continue;
+				const firstColon = header.indexOf(':');
+				if (firstColon === -1) {
+					throw new Error(`Invalid header: "${header}"`);
+				}
+				const key = header.slice(0, firstColon).toLowerCase();
+				const value = header.slice(firstColon + 1).trimStart();
+				const current = headers[key];
+				if (typeof current === 'string') {
+					headers[key] = [current, value];
+				} else if (Array.isArray(current)) {
+					current.push(value);
+				} else {
+					headers[key] = value;
+				}
+			}
 			debug('got proxy server response: %o', firstLine);
 			cleanup();
 			resolve({
-				statusCode,
+				connect: {
+					statusCode,
+					statusText,
+					headers,
+				},
 				buffered,
 			});
 		}

packages/https-proxy-agent/test/test.ts

@@ -106,7 +106,13 @@ describe('HttpsProxyAgent', () => {
 
 			const agent = new HttpsProxyAgent(proxyUrl);
 
-			const res = await req(serverUrl, { agent });
+			const r = req(serverUrl, { agent });
+			const [connect] = await once(r, 'proxyConnect');
+			expect(connect.statusCode).toEqual(200);
+			expect(connect.statusText).toEqual('Connection established');
+			expect('date' in connect.headers).toBe(true);
+
+			const res = await r;
 			const body = await json(res);
 			assert.equal(serverUrl.host, body.host);
 		});