index.js

const express = require('express')
const http = require('http')
const { Server: SocketIO } = require('socket.io')
const shortid = require('shortid')

const app = express()
const server = http.Server(app)
const io = new SocketIO(server)
const port = process.env.PORT || 3000
const Room = function (user) {
  this.id = shortid.generate()
  this.users = new Set([user])
  return this
}
Room.prototype.addUser = function (newUser) {
  this.users.add(newUser)
  return this
}
Room.prototype.removeUser = function (user) {
  this.users.delete(user)
  return this
}
Room.prototype.getUserCount = function () {
  return this.users.size
}
Room.prototype.getId = function () {
  return this.id
}
Room.prototype.toString = function () {
  return `${this.id} - ${this.users.size}`
}
const RoomList = function () {
  this.rooms = []
}
RoomList.prototype.addRoom = function (user) {
  const newRoom = new Room(user)
  this.rooms.push(newRoom)
  return newRoom.id
}
RoomList.prototype.removeRoom = function (roomId) {
  this.rooms.splice(this.rooms.findIndex(room => room.id === roomId), 1)
}
RoomList.prototype.removeUserFromRoom = function (user, roomId) {
  if (
    this
      .findById(roomId)
      .removeUser(user)
      .getUserCount() === 0
  ) {
    this.removeRoom(roomId)
  }
  return this
}
RoomList.prototype.roomExist = function (roomId) {
  return Boolean(this.findById(roomId))
}
RoomList.prototype.addUserToRoom = function (user, roomId) {
  const room = this.findById(roomId)
  if (room.getUserCount() === 1) {
    room.addUser(user)
    return true
  }
  return false
}
RoomList.prototype.findById = function (roomId) {
  return this.rooms.find(room => room.getId() === roomId)
}
RoomList.prototype.toString = function () {
  return this.rooms.join(', ')
}
const roomList = new RoomList()

app.use(express.static(`${__dirname}/client/public`))

io.on('connection', socket => {
  let roomId = socket.handshake.query.roomId
  console.log(`User Connected, roomId: ${roomId}`)

  if (roomId && roomList.roomExist(roomId)) {
    const added = roomList.addUserToRoom(socket.id, roomId)
    if (added) {
      socket.join(roomId)
      socket.broadcast.to(roomId).emit('join')
      console.log(`User enter the room. ${roomList}`)
    } else {
      socket.emit(
        'tryAnotherRoom',
        'No one needs you here... This is a cruel world, what did you expect?'
      )
      roomId = roomList.addRoom(socket.id)
      socket.join(roomId)
      console.log(`New room added, user joined, roomList: ${roomList}`)
      socket.emit('room', roomId)
    }
  } else {
    if (roomId) {
      socket.emit(
        'tryAnotherRoom',
        'That room does not exist'
      )
    }
    roomId = roomList.addRoom(socket.id)
    socket.join(roomId)
    console.log(`New room added, user joined, roomList: ${roomList}`)
    socket.emit('room', roomId)
  }
  socket.on('message', msg => socket.broadcast.to(roomId).emit('message', msg))
  socket.on('disconnect', () => {
    roomList.removeUserFromRoom(socket.id, roomId)
    socket.broadcast.to(roomId).emit('tryAnotherRoom', 'Your friend is left the building...')
    console.log(`User Disconnected, roomList: ${roomList}`)
  })
})

server.listen(port, () => {
  console.log(`[INFO] Server is running on: http://localhost:${port}`)
})