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
const 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 quotaTimes;

    const quota = totalCount / memeCount.length; // Квота мемов на человека
    console.log(`${totalCount} мемов всего. Квота: ${quota}`);

    function activeUsers() {
      let count = 0;
      memeCount.forEach((person) => {
        if (person.count > quota / 10) { count += 1; }
      });
      return count;
    }

    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;
      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 {
      /* eslint-disable no-await-in-loop */
      card = await cardsCollection.aggregate([
        {
          $sample: { size: 1 },
        }, {
          $unset: ['name', 'link', 'date'],
        },
      ]).toArray();
      /* eslint-enable no-await-in-loop */
      [card] = card;
    } 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) => 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 += 1;
        } else {
          req.session.wrong += 1;
        }
        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}`));