rewrite XhrListener to use Express

src/config/app.ts

@@ -4,7 +4,6 @@ module.exports = {
   secret : process.env.SECRET || 'test',
   devToken: 'eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJkYXRhIjp7ImNsaWVudCI6InRlc3QiLCJjbGllbnRfdHlwZSI6InNpdGUiLCJ1c2VyX3R5cGUiOiJ1c2VyIiwidXNlcl9pZCI6MjAwLCJjaGFubmVsIjoidGVzdF9jaGFubmVsIn0sImF1ZCI6ImludGVybmFsIiwiaXNzIjoiWWFyZHN0aWNrIFNvZnR3YXJlIiwic3ViIjoiQnJhaWQgSldUIn0.5KNCov_EW1cycT4Ay0oSvk4Z4PHFedd3bWOyqkHHTBQ',
   port: process.env.PORT || 80,
-  httpPort: process.env.HTTP_PORT || 8080,
   hostname: process.env.HOSTNAME || 'ysbraid.localhost',
   environment: process.env.ENVIRONMENT || 'development',
   log_level: process.env.LOG_LEVEL || 'debug',

src/server.ts

@@ -2,10 +2,12 @@
 import * as WebSocket from 'ws';
 import * as jwt from 'jsonwebtoken';
 import * as url from 'url';
+import * as express from 'express';
 
 // internal imports
 const app = require('./config/app');
 const logger = require('./logger');
+const http = require('http');
 
 import ClientManager from './clientManager';
 import ChannelManager from './channelManager';
@@ -14,10 +16,15 @@ import PublicClient from './clients/types/publicClient';
 import PrivateClient from './clients/types/privateClient';
 import CustomClient from './clients/types/customClient';
 
-const wss = new WebSocket.Server({ maxPayload: 250000, port: app.port });
+const appExpress = express();
+const server = new http.createServer();
+// the port is no longer specified here as it induces WS to start running on its own
+// instead, we do it later in XhrListener
+const wss = new WebSocket.Server({ server: server, maxPayload: 250000 });
+
 const clientManager = new ClientManager();
 const channelManager = new ChannelManager();
-const xhrListener = new XhrListener(channelManager);
+const xhrListener = new XhrListener(channelManager, server, appExpress, express.json({type: 'application/json'}));
 
 function connectionManager() {
   wss.on('connection', (ws: WebSocket, request: any, args: string) => {

src/xhrListener.ts

@@ -5,9 +5,10 @@ const url = require('url');
 const http = require('http');
 const crypto = require('crypto');
 const app = require('./config/app');
+const cors = require('cors');
 
 const AUTH_TOKEN = app.archimedesToken;
-const HTTP_PORT = app.httpPort;
+const HTTP_PORT = app.port;
 
 import { Server, IncomingMessage, ServerResponse } from 'http'
 
@@ -19,14 +20,55 @@ interface ArchimedesMessage {
 class XhrListener {
   #cm: ChannelManager;
 
-  constructor(cm: ChannelManager) {
+  constructor(cm: ChannelManager, server: any, app: any, jsonParser: any) {
+
+    this.#cm = cm;
+    logger.debugLog.info("XhrListener running");
+
+    app.use(jsonParser);
+
+    // TODO: try to pin down origin to reflect client rather than use wildcard
+    app.options('*', cors());
+
     // I'm not entirely happy with bind(this) but it does let me break the
     // callback and event handlers out into class methods. It will be
     // problematic if the actual `this` needs to be accessed.
-    let xhrlisten = http.createServer(this.onRequest.bind(this));
+
-    xhrlisten.listen(HTTP_PORT);
+    app.post('/event/resume', cors(),
-    this.#cm = cm;
+      (req: any, res: any, next: any) => this.eventFromArchimedes.bind(this)("resumeExam", req, res));
-    logger.debugLog.info("XhrListener running");
+    app.post('/event/pause', cors(),
+      (req: any, res: any, next: any) => this.eventFromArchimedes.bind(this)("pauseExam", req, res));
+
+    server.on('request', app);
+
+    // note that this kicks off HTTP listen for the entire app - not just HTTP but WS as well!
+    server.listen(HTTP_PORT, () => logger.debugLog.info(`braid is now listening for HTTP and WS connections on port ${HTTP_PORT}`));
+  }
+
+  public authorized(authOffered: String): boolean {
+    return AUTH_TOKEN === authOffered;
+  }
+
+  public eventFromArchimedes(eventType: string, req: any, res: any) {
+    logger.debugLog.info(`eventFromArchimedes("${eventType}") called`);
+    let authorized: boolean = this.authorized(req.headers['x-proctoru-signature']);
+
+    if (!authorized) {
+      res.status(401);
+      res.send("Unauthorized");
+      return;
+    }
+
+    res.setHeader('Content-Type', 'application/json');
+    let amsg: ArchimedesMessage = { 'examId': req.body.examId, 'reservation_no': req.body.reservation_no };
+    if (this.relayEvent(eventType, amsg)) {
+      logger.debugLog.info('200 success relaying ' + eventType);
+      res.send(JSON.stringify(`${eventType} event was successfully relayed`));
+    } else {
+      logger.errorLog.info(`XhrListener: could not relay ${eventType} event "${amsg}" to Exam UI; body: "${req.body}"`);
+      res.status(400);
+      res.send(JSON.stringify(`error while relaying ${eventType} event`));
+    }
   }
 
   public relayEvent(event: string, archMsg: ArchimedesMessage): boolean {
@@ -50,77 +92,6 @@ class XhrListener {
     // did not match a channel; examId isn't valid for some reason
     return false;
   }
-
-  public onRequestEnded(body: Uint8Array[], request: IncomingMessage, response: ServerResponse): void {
-    logger.debugLog.info("XhrListener:onRequestEnded()");
-    if (request.method === 'OPTIONS') {
-      logger.debugLog.info("handling CORS preflight");
-      // CORS: implement permissive policy for XHR clients
-      response.setHeader('Access-Control-Allow-Origin', request.headers['origin'] || "*");
-      response.setHeader('Access-Control-Allow-Methods', request.headers['access-control-request-methods'] || "OPTIONS, GET, POST");
-      response.setHeader('Access-Control-Allow-Headers', request.headers['access-control-request-headers'] || "Content-Type");
-      response.setHeader('Access-Control-Allow-Credentials', "true");
-      response.end();
-    } else {
-      logger.debugLog.info("parsing Archimedes event: " + body);
-      let endpoint = url.parse(request.url).pathname
-      let returnVal: [number, string] = [-1, ""];
-      let authorized: boolean = request.headers['x-proctoru-signature'] === AUTH_TOKEN;
-
-      // body of POST is JSON: '{"examId":"proctor_u_id", "reservation_no":"primary_key_from_archimedes"}'
-      switch (true) {
-        // match /event/pause*
-        case /^\/event\/pause([/]+.*)*$/.test(endpoint):
-          if (authorized) {
-            let amsg: ArchimedesMessage = JSON.parse(Buffer.concat(body).toString());
-            if (this.relayEvent("pauseExam", amsg)) {
-              returnVal = [200, "pause event was successfully relayed"];
-            } else {
-              logger.errorLog.info(`XhrListener: could not relay pause event "${amsg}" to Exam UI; body: "${body}"`);
-              returnVal = [400, "error while relaying pause event"];
-            }
-          }
-
-          break;
-
-        // match /event/resume*
-        case /^\/event\/resume([/]+.*)*$/.test(endpoint):
-          if (authorized) {
-            let amsg: ArchimedesMessage = JSON.parse(Buffer.concat(body).toString());
-            if (this.relayEvent("resumeExam", amsg)) {
-              returnVal = [200, "resume event was successfully relayed"];
-            } else {
-              logger.errorLog.info(`XhrListener: could not relay resume event "${amsg}" to Exam UI; body: "${body}"`);
-              returnVal = [400, "error while relaying resume event"];
-            }
-          }
-          break;
-
-        default:
-          logger.errorLog.info(`XhrListener: bad event or other request; body: "${body}"`);
-          returnVal = [400, "Bad request"];
-          break;
-      };
-
-      if (-1 == returnVal[0]) {
-        response.writeHead(authorized ? 400 : 401);
-        response.end();
-      } else {
-        response.writeHead(returnVal[0], { 'Content-Type': 'application/json' });
-        response.end(JSON.stringify(returnVal[1]));
-      }
-    }
-  }
-
-  private onRequest(request: IncomingMessage, response: ServerResponse): void {
-    logger.debugLog.info("XhrListener:onRequest()");
-    let body: Uint8Array[] = [];
-    request.on('data', post_block => body.push(post_block));
-
-    request.on('end', () => {
-      this.onRequestEnded(body, request, response);
-    });
-  }
 }
 
 export default XhrListener;