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 });

(async () => {
  await client.connect();
  const cardsCollection = client.db(process.env.DB_NAME).collection('cards');
  const answersCollection = client.db(process.env.DB_NAME).collection('answers');

  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,
    },
  }));

  // Выравнивание вероятности
  // Объект хранящий вероятности с которой карта каждого участника отбрасывается
  const dropProb = {};
  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}`));
})();