server.js

const request = require("request");
// const cors = require('cors');
const express = require("express");
const bodyParser = require("body-parser");
const app = express();
const http = require("http").Server(app);
const io = require("socket.io")(http);

app.use(express.static("dist", { index: "demo.html", maxage: "4h" }));
app.use(bodyParser.json());

const sessions = {};
const buffer = {};
// const historyIds = []

// handle admin Telegram messages
app.post(`/hook`, function (req, res) {
  try {
    const message = req.body.message || req.body.channel_post;
    const chatId = process.env.TELEGRAM_CHAT_ID; // || message.chat.id;
    let name = message.from.first_name || message.chat.first_name || "Support";
    const text = message.text || "";
    const reply = message.reply_to_message;

    // console.log(JSON.stringify(req.body));

    if (/(adriaan|simple)/gi.test(name)) name = "Adriaan";

    if (text.startsWith("/start")) {
      // console.log('/start chatId ' + chatId);
      sendTelegramMessage(
        chatId,
        "*Welcome to Intergram* \n" +
          "Your unique chat id is `" +
          chatId +
          "`\n" +
          "Use it to link between the embedded chat and this telegram chat",
        "Markdown"
      );
    } else if (reply) {
      let replyText = reply.text || "";
      let userId = replyText.split(":")[0];
      const socketId = sessions[userId];

      if (socketId) {
        io.to(socketId).emit(chatId + "-" + userId, {
          name,
          text,
          from: "admin",
        });
      } else {
        if (!buffer[userId]) {
          buffer[userId] = [];
        }

        console.log("client not connected buffering message");
        buffer[userId].unshift({
          chatId,
          name,
          text,
          from: "admin",
          adminName: name,
        });
      }
    } else if (text) {
      // io.emit(chatId, {name, text, from: 'admin'});
    }
  } catch (e) {
    console.error("hook error", e, req.body);
  }
  res.statusCode = 200;
  res.end();
});

// handle chat visitors websocket messages
io.on("connection", function (socket) {
  socket.on("register", function (registerMsg) {
    console.log("on register");
    let userId = registerMsg.userId;
    let chatId = registerMsg.chatId;
    // let messageReceived = false;

    sessions[userId] = socket.id;

    // if (historyIds.indexOf(userId) > -1) {
    //   messageReceived = true;
    //   sendTelegramMessage(chatId, `${userId}: re-opened chat`, null, true);
    // }

    if (buffer[userId]) {
      const buffered = buffer[userId];
      let msg = buffered.pop();
      console.log(`sending ${buffered.length} buffered messages`);
      while (msg) {
        const { chatId, name, text, from, adminName } = msg;
        io.to(socket.id).emit(chatId + "-" + userId, {
          name,
          text,
          from,
          adminName,
        });
        msg = buffered.pop();
      }
      delete buffer[userId];
    }

    socket.on("message", function (msg) {
      // console.log('on message', msg)
      messageReceived = true;
      // if (msg.from !== 'bot') io.emit(chatId + '-' + userId, msg);
      if (msg.from !== "bot") io.to(socket.id).emit(chatId + "-" + userId, msg);
      sendTelegramMessage(chatId, `${userId}: ${msg.text}`);
    });

    socket.on("disconnect", function () {
      // console.log('on disconnect')
      // if (historyIds.indexOf(userId) === -1) historyIds.push(userId)
      // if (messageReceived) {
      //   sendTelegramMessage(chatId, `${userId}: has left`, null, true);
      // }
      delete sessions[userId];
    });
  });
});

function sendTelegramMessage(
  chatId,
  text,
  parseMode,
  disableNotification = false
) {
  const data = {
    disable_notification: disableNotification,
    chat_id: chatId,
    text,
  };
  if (parseMode) data.parse_mode = parseMode;

  request
    .post(
      "https://api.telegram.org/bot" +
        process.env.TELEGRAM_TOKEN +
        "/sendMessage"
    )
    .form(data)
    .on("error", function (err) {
      console.error(err);
    });
}

// app.post('/usage-start', cors(), function(req, res) {
//   console.log('usage from', req.query.host);
//   res.statusCode = 200;
//   res.end();
// });

// // left here until the cache expires
// app.post('/usage-end', cors(), function(req, res) {
//   res.statusCode = 200;
//   res.end();
// });

http.listen(process.env.PORT || 3001, function () {
  console.log("listening on port:" + (process.env.PORT || 3001));
});