const express = require('express');
const sha512 = require('js-sha512');
const shortid = require('shortid');
const base64 = require('base-64');

const db = require('./db');

const buildSessionCookie = ({ username, sessionToken, isLogout, remember }) => {
  if (!isLogout) {
    const joinedToken = `${username}&${sessionToken}`;
    const encodedToken = base64.encode(joinedToken);
    if (remember) {
      return `sessionCookie=${encodedToken}; Domain=localhost; HttpOnly; SameSite=strict;`;
    } else {
      return `sessionCookie=${encodedToken}; Domain=localhost; HttpOnly; SameSite=strict; Max-Age=86400;`;
    }
  } else {
    return `sessionCookie=deleted; Domain=localhost; Expires=Thu, 01 Jan 1970 00:00:00 GMT; HttpOnly; SameSite=strict;`;
  }
};

const normalRouter = express.Router();
const authedRouter = express.Router();

authedRouter.use(async (req, res, next) => {
  const cookies = req.cookies;
  const encodedCookie = cookies.sessionCookie;

  if (!encodedCookie) {
    res.status(403);
    return res.json({
      message: 'Log in first!',
    });
  }
  const sessionCookie = base64.decode(encodedCookie);

  const [ username, sessionToken ] = sessionCookie.split('&');

  const user = await db('users').where({ username }).first();
  if (!user) {
    res.status(400);
    res.set('Set-Cookie', buildSessionCookie({ isLogout: true }));
    return res.json({
      message: 'Invalid session token.',
      sessionCookie,
    });
  }

  const salt = user.salt;

  const sessionTokenHash = sha512(salt + sessionToken);
  const token = await db('tokens').where({ type: 'session', value: sessionTokenHash });
  if (!token) {
    res.status(400);
    res.set('Set-Cookie', buildSessionCookie({ isLogout: true }));
    return res.json({
      message: 'Invalid session token.',
      sessionCookie,
    });
  }

  req.sessionTokenHash = sessionTokenHash;
  req.user = user;

  next();
});

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

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

  const existingUser = await db('users').where({ username }).first();
  if (existingUser) {
    res.status(400);
    return res.json({
      error: 'Username already taken.',
    });
  }

  const salt = shortid.generate();
  const pwHash = sha512(salt + password);

  const sessionToken = shortid.generate();
  const sessionTokenHash = sha512(salt + sessionToken);

  const user = (await db('users').insert({ username, password: pwHash, salt }).returning('*'))[0];
  await db('tokens').insert({ user_id: user.id, type: 'session', value: sessionTokenHash });

  res.set('Set-Cookie', buildSessionCookie({ username, sessionToken, remember: false, isLogout: false }));
  return res.json({
    username,
  });
});

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

  const user = await db('users').where({ username }).first();

  if (user) {
    const sessionToken = shortid.generate();
    const sessionTokenHash = sha512(user.salt + sessionToken);

    await db('tokens').insert({ user_id: user.id, type: 'session', value: sessionTokenHash });

    res.set('Set-Cookie', buildSessionCookie({ username, sessionToken, remember, isLogout: false }));

    return res.json({
      username,
    });
  }

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

authedRouter.post('/logout', async (req, res) => {
  await db('tokens').where({ type: 'session', user_id: req.user.id, value: req.sessionTokenHash }).delete();
  res.status(204);
  res.set('Set-Cookie', buildSessionCookie({ isLogout: true }));
  res.send();
});

authedRouter.get('/user', (req, res) => {
  const user = req.user;
  return res.json({
    message: `Hello user ${user.username}!`,
    username: user.username,
  });
});

module.exports = { authedRouter, normalRouter };