web-drs-backend/server.node.ts

import * as fs from "fs";
import * as https from "https";
import { WebSocketServer } from "ws";

import * as crypto from "crypto";

import type {
  AckMessage,
  IdResponseMessage,
  TextMessage,
  TypingMessage,
} from "./lib/ServerMessage";

import {
  isServerMessage,
  isTextMessage,
  isTypingMessage,
  MessageType,
} from "./lib/ServerMessage";

const port = 8085;
const timeout = 15000;
const typingTimeout = 2000;

const httpsServer = https.createServer({
  key: fs.readFileSync("./key.pem"),
  cert: fs.readFileSync("./cert.pem"),
});
const webSocketServer = new WebSocketServer({ server: httpsServer });

/* If not using SSL/TLS
const webSocketServer = new WebSocketServer({ port });
*/

console.log("listening on port: " + port);

async function handleTextMessage(message: TextMessage, from: string) {
  for (const to of webSocketServer.clients) {
    to.send(
      JSON.stringify(
        Object.assign({}, message, {
          author: from,
        })
      )
    );
  }
}

const activeConnections = new Set<string>();
const currentlyTyping = new Set<string>();
const currentlyTypingTimeouts = new Map<string, ReturnType<typeof setTimeout>>();

async function handleTypingMessage(_message: TypingMessage, from: string) {
  currentlyTyping.add(from);

  if(currentlyTypingTimeouts.has(from)) {
    clearTimeout(currentlyTypingTimeouts.get(from)!);
  }
  currentlyTypingTimeouts.set(from, setTimeout(() => {
    currentlyTyping.delete(from);
    currentlyTypingTimeouts.delete(from);
    sendCurrentlyTypingMessage(from, true);
  }, typingTimeout));
  sendCurrentlyTypingMessage(from);
}

async function sendCurrentlyTypingMessage(from?: string, stopped = false) {
  for (const to of webSocketServer.clients) {
    to.send(
      JSON.stringify(
        Object.assign({
          type: MessageType.CURRENTLY_TYPING,
          date: Date.now(),
        }, {
          currently: Array.from(currentlyTyping.values()),
        }, from === undefined ? {
          __ctx: "regular update",
        } : {
          __ctx: from + (stopped ? " stopped typing" : " started typing"),
        })
      )
    )
  }
}

async function handleCloseConnection(id: string) {
  activeConnections.delete(id);
}

webSocketServer.on("connection", function connection(socket) {
  const close = (reason: string, code: number = 1000) => {
    socket.send(
      JSON.stringify({
        type: MessageType.ACK,
        date: Date.now(),
        __ctx: `closing connection. reason: ${reason}`,
      } as AckMessage)
    );
    socket.close(code, `closing connection. reason: ${reason}`);
    handleCloseConnection(authorId);
  };

  const authorId: string = crypto.randomUUID();

  socket.on("message", function (rawMessage: string) {
    const message = JSON.parse(rawMessage);
    if (!isServerMessage(message)) {
      console.error(`Unexpected message received from client "${authorId}": \`${message}\``);
      return;
    }

    if (isTextMessage(message)) {
      if (message.author === authorId) {
        handleTextMessage(message, authorId);
      }
    } else if (isTypingMessage(message)) {
      handleTypingMessage(message, authorId);
    }

    clearTimeout(closeTimeout);
    closeTimeout = setTimeout(close, timeout);
  });
  socket.on("close", function close() {
    console.log("closed a connection");
  });

  console.log("new client connected! ID:", authorId);
  socket.send(
    JSON.stringify({
      type: MessageType.ID_RESPONSE,
      __ctx: "connected successfully",
      date: Date.now(),
      authorId,
    } as IdResponseMessage)
  );
  activeConnections.add(authorId);
  let closeTimeout = setTimeout(close, timeout);
});

httpsServer.listen(port);