vk-bingo/backend/index.js

const express = require('express')
const session = require('express-session')
const app = express()
const { MongoClient, ObjectId } = require('mongodb')
const MongoStore = require('connect-mongo')
const cors = require('cors')
require('dotenv').config()

app.use(cors({
  origin: [
    process.env.FRONTEND,
  ],
  credentials: true,
  exposedHeaders: ['set-cookie']
}))
app.use(express.json())
app.use(express.urlencoded({ extended: true }))

const names = require('./names.json')
const client = new MongoClient(process.env.URI, { useUnifiedTopology: true })

app.use(session({
  secret: process.env.SECRET,
  resave: false,
  saveUninitialized: true,
  store: MongoStore.create({
    client,
    dbName: process.env.DB_NAME
  }),
  cookie: { 
    secure: false,
    maxAge: 1000 * 60 * 60 * 24
  }
}))

client.connect()
const cardsCollection = client.db(process.env.DB_NAME).collection('cards')
const answersCollection = client.db(process.env.DB_NAME).collection('answers')

// Выравнивание вероятности
let dropProb = {} // Объект хранящий вероятности с которой карта каждого участника отбрасывается
cardsCollection.aggregate([
  {
    '$group': {
      '_id': '$name', 
      'count': {
        '$sum': 1
      }
    }
  }
]).toArray().then((memeCount) => {
  cardsCollection.countDocuments().then((totalCount) => {
    let quota, quotaTimes

    quota = totalCount/memeCount.length  // Квота мемов на человека
    console.log(totalCount + " мемов всего. Квота: " + quota)

    function activeUsers() {
      let activeUsers = 0
      memeCount.forEach((person) => {
        if (person.count > quota/10)
          activeUsers++
      })
      return activeUsers
    }

    memeCount.forEach((person) => {
      // Во сколько раз превышена квота:
      // (колич. астивных человек в конфе * колич. мемов данного человека / мемов всего)
      quotaTimes = activeUsers()*person.count/totalCount
      if (quotaTimes > 1) {
        dropProb[person._id] = 1 - (1/quotaTimes)
      } else {
        dropProb[person._id] = 0
      }
      console.log(person._id + " ["+person.count+"]: " + dropProb[person._id])
    })
  })
})

app.post('/api/auth', async (req, res) => {
  if (req.session.loggedIn) {
    res.status(200).send("Logged in")
  } else {
    try {
      const pass = req.body.pass
      if (pass && pass.toLowerCase() === process.env.PASSWORD) {
        req.session.loggedIn = true
        res.status(200).send("Logged in")
      } else {
        res.status(401).send("Wrong password")
      }
    } catch (e) {
      console.log("Error: " + e)
      res.status(500).send()
    }
  }
})

app.get('/api/card', async (req, res) => {
  async function drawCard() {
    let card
    // Тянем карты и отбрасываем их в соответствии с их вероятностью отбрасывания
    do {
      card = await cardsCollection.aggregate([
        {
          $sample: { size: 1 }
        }, {
          $unset: [ 'name', 'link', 'date' ]
        }
      ]).toArray()
      card = card[0]
    } while (Math.random() < dropProb[card.name])
    return card
  }

  if (req.session.loggedIn) {
    res.status(200).send(await drawCard())
  } else {
    res.status(403).send()
  }
})

app.get('/api/meme', async (req, res) => {
  const amount = Number(req.query.amount) || 1
  try {
    let cards = await cardsCollection.aggregate([{ $sample: { size: amount } }]).toArray()
    // Удаляем конфиденциальную информацию
    cards = cards.map((card) => {
      return card.image
    })
    res.status(200).send(cards)
  } catch (e) {
    console.log("Error: " + e)
    res.status(500).send()
  }
})

app.post('/api/answer', async (req, res) => {
  if (req.session.loggedIn) {
    if (req.body.data.id && req.body.data.name) {
      const card = await cardsCollection.findOne({ _id: ObjectId(req.body.data.id) })
      if (card) {
        const correct = card.name === req.body.data.name
        if (correct) {
          req.session.right++ 
        } else {
          req.session.wrong++
        }
        answersCollection.insertOne({ 
          correct,
          selected: req.body.data.name
        })
        res.status(200).send({
          correct,
          card
        })
      } else {
        res.status(500).send() 
      }
    } else {
      res.status(400).send()  
    }
  } else {
    res.status(403).send()
  }
})

app.get('/api/score', (req, res) => {
  if (req.session.loggedIn) {
    req.session.right = req.session.right || 0
    req.session.wrong = req.session.wrong || 0
    const scoreObj = {
      "right": req.session.right,
      "wrong": req.session.wrong
    }
    res.status(200).send(scoreObj)
  } else {
    res.status(403).send()
  }
})

app.get('/api/stats', async (req, res) => {
  if (req.session.loggedIn) {
    answersCollection.aggregate([
      {
        '$group': {
          '_id': '$selected', 
          'correct': {
            '$sum': {
              '$cond': [
                '$correct', 1, 0
              ]
            }
          }, 
          'wrong': {
            '$sum': {
              '$cond': [
                '$correct', 0, 1
              ]
            }
          }
        }
      }
    ]).toArray().then(stats => res.status(200).send(stats))
  } else {
    res.status(403).send()
  }
})

app.get('/api/options', async (req, res) => {
  if (req.session.loggedIn) {
    res.status(200).send(names)
  } else {
    res.status(403).send()
  }
})

app.listen(process.env.PORT, () => console.log('Server started on ' + process.env.PORT));