'use strict';
const mysql = require('mysql');

const Q = {
  'GET_USER': 'SELECT username, password FROM users WHERE username = ?',
  'ADD_USER': 'INSERT INTO users (username, password) VALUES (?, ?)'
};

const E = {
  'BAD_ADD': 'An error occured when adding your credentials to the database.',
  'BAD_VALIDATION': 'An error occured when validating your credentials.',
  'WRONG_CREDENTIALS': 'Your username or password was wrong.'
};

const pool = mysql.createPool({
  connectionLimit: 20,
  host: 'localhost',
  user: 'developer',
  password: 'developer',
  database: 'chat-app'
});

function query(query, args) {
  return new Promise((resolve, reject) => {
    pool.query(query, args, (err, res) => {
      if (err) return reject(err);
      return resolve(res);
    });
  });
}

exports.addUser = (user, cb) => {
  query(Q.ADD_USER, [user.username, user.password])
  .then(resultSet => cb(null, resultSet))
  .catch(error => cb(E.BAD_ADD, null));
}

exports.validateUser = (user, cb) => {
  query(Q.GET_USER, [user.username])
  .then(resultSet => {
    if (user.password === resultSet[0].password) return cb(null, true);
    return cb(E.WRONG_CREDENTIALS, false);
  })
  .catch(error => cb(E.BAD_VALIDATION, null));
}