feat(httphandshake): added logic for implementing server initial http handshake response

Logic for headers needed was implemented following the official spec at
https://www.rfc-editor.org/rfc/rfc6455.html#section-4.2.2

Author: amscu-dev

src/index.ts

@@ -9,6 +9,7 @@ import CONFIG from "@/config/app.config";
 import * as CONSTANTS from "@/libs/custom_lib/constants/constants";
 
 import sendUpgradeErrorResponse from "./libs/custom_lib/sendUpgradeErrorResponse";
+import { upgradeHttpConnection } from "./libs/custom_lib/upgradeHttpConnection";
 import UpgradeValidatorFactory from "./libs/custom_lib/validateHttpHandshake";
 import handleProcessErrors from "./utils/handleProcessErrors";
 
@@ -45,8 +46,8 @@ httpServer.listen(CONFIG.PORT, CONFIG.HOST, () => {
 
 // handle inital http handshake in order to establish a ws connection
 // Docs: https://nodejs.org/docs/latest/api/http.html#event-upgrade_1
-// eslint-disable-next-line @typescript-eslint/no-unused-vars
-httpServer.on("upgrade", (request, socket, _head) => {
+
+httpServer.on("upgrade", (request, socket) => {
   // Parsing required client request headers in conformity with https://www.rfc-editor.org/rfc/rfc6455.html#section-4.1
   const validationResult = upgradeValidator.validate(request);
   // https://www.rfc-editor.org/rfc/rfc6455.html#section-4.2.1
@@ -58,6 +59,7 @@ httpServer.on("upgrade", (request, socket, _head) => {
     );
     return;
   }
+  upgradeHttpConnection(request, socket);
 });
 
 // implement basic error handling

src/libs/custom_lib/constants/constants.ts

@@ -16,3 +16,5 @@ export const upgradeConfig: UpgradeConfig = {
   method: "GET",
   allowedOrigins: ["http://127.0.0.1:5500", "http://localhost:5500"],
 };
+
+export const GUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";

src/libs/custom_lib/upgradeHttpConnection.ts

@@ -0,0 +1,83 @@
+import crypto from "node:crypto";
+import http from "node:http";
+import { Duplex } from "node:stream";
+
+import * as CONSTANTS from "@/libs/custom_lib/constants/constants";
+
+class UpgradeHeadersBuilder {
+  private headers: Record<string, string> = {};
+
+  constructor(request: http.IncomingMessage) {
+    this.buildDefaultHeaders(request);
+  }
+
+  private buildDefaultHeaders(request: http.IncomingMessage): void {
+    const secWebSocketKey = request.headers["sec-websocket-key"] || "";
+    const data = secWebSocketKey + CONSTANTS.GUID;
+    const hash = crypto.createHash("sha1").update(data).digest("base64");
+
+    this.headers = {
+      Upgrade: "websocket",
+      Connection: "Upgrade",
+      "Sec-WebSocket-Accept": hash,
+    };
+  }
+
+  addHeader(name: string, value: string): this {
+    this.headers[name] = value;
+    return this;
+  }
+
+  build(): Record<string, string> {
+    return this.headers;
+  }
+}
+
+class HttpResponseBuilder {
+  private statusCode: number = 101;
+  private statusText: string = "Switching Protocols";
+  private headers: Record<string, string>;
+
+  constructor(headers: Record<string, string>) {
+    this.headers = headers;
+  }
+
+  setStatus(code: number, text: string): this {
+    this.statusCode = code;
+    this.statusText = text;
+    return this;
+  }
+
+  addHeader(name: string, value: string): this {
+    this.headers[name] = value;
+    return this;
+  }
+
+  build(): string {
+    const statusLine = `HTTP/1.1 ${this.statusCode} ${this.statusText}\r\n`;
+    const headerLines = Object.entries(this.headers)
+      .map(([key, value]) => `${key}: ${value}`)
+      .join("\r\n");
+
+    return statusLine + headerLines + "\r\n\r\n";
+  }
+}
+
+function startWebSocketConnection(socket: Duplex) {
+  console.log(socket);
+}
+
+export function upgradeHttpConnection(
+  request: http.IncomingMessage,
+  socket: Duplex,
+): void {
+  const headers = new UpgradeHeadersBuilder(request).build();
+
+  const response = new HttpResponseBuilder(headers)
+    .setStatus(101, "Switching Protocols")
+    .build();
+
+  socket.write(response);
+
+  startWebSocketConnection(socket);
+}