const express = require('express');
const router = express.Router();
const sha512 = require('js-sha512');
const shortid = require('shortid');

const salt = 'suola';

const low = require('lowdb');
const FileSync = require('lowdb/adapters/FileSync');

const adapter = new FileSync('db.json');
const db = low(adapter);

db.defaults({ users: [] }).write();

router.get('/', (req, res) => {
  res.json({
    message: 'Backend API',
  });
});

router.post('/register', (req, res) => {
  const { username, password } = req.body;
  if (!username || !password) {
    res.status(400);
    return res.json({
      error: 'Username or password missing.',
    });
  }

  const user = db.get('users').find({ username }).value();
  if (user) {
    res.status(400);
    return res.json({
      error: 'Username already taken.',
    });
  }

  const pwHash = sha512(salt + password);
  db.get('users').push({ username, password: pwHash }).write();
  return res.json({
    username,
  });
});

router.post('/login', (req, res) => {
  const { username, password } = req.body;
  if (!username || !password) {
    res.status(400);
    return res.json({
      error: 'Username or password missing.',
    });
  }

  const userObj = db.get('users').find({ username });
  const user = userObj.value();

  if (user) {
    const sessionId = shortid.generate();
    userObj.assign({ sessionId }).write();
    res.set('Set-Cookie', `sessionId=${sessionId}`);
    return res.json({
      username,
    });
  }

  res.status(403);
  res.json({
    error: 'Wrong username or password',
  });
});

router.post('/logout', (req, res) => {
  const cookies = req.cookies;
  const { sessionId } = cookies;

  const userObj = db.get('users').find({ sessionId });
  if (userObj) {
    userObj.assign({ sessionId: null }).write();
  }
  res.status(204);
  res.set('Set-Cookie', 'sessionId=deleted; expires=Thu, 01 Jan 1970 00:00:00 GMT');
  res.send();
});

router.get('/user', (req, res) => {
  const cookies = req.cookies;
  const { sessionId } = cookies;

  if (!sessionId) {
    res.status(403);
    return res.json({
      message: 'Log in first!',
    });
  }

  const userObj = db.get('users').find({ sessionId });
  const user = userObj.value();

  if (userObj) {
    return res.json({
      message: `Hello user ${user.username}!`,
      username: user.username,
    });
  }

  res.status(400);
  return res.json({
    message: 'Invalid session token.',
    sessionId,
  });
});

module.exports = router;