const mysql = require("mysql2/promise")

const {host, port, user, database, password} = require("./../settings").db

/////////////////////////////////////////////////////////////////////////

let poolP = initPool()

async function initPool () {
   return mysql.createPool({
      host,
      port,
      database,
      user,
      password,
   })
}

/////////////////////////////////////////////////////////////////////////

module.exports = {
   getUsers,
   getUserCount,
   getUserByLogin,
   getUserByUserId,
   getUserDefinedFields,
   getUserDefinedField,
}

/////////////////////////////////////////////////////////////////////////

async function getUsers (offset = 0, limit = 10) {
   const sel = `usr_id, login, firstname, lastname, gender, email, institution, street, city, zipcode, country, department, active`
   // TODO user defined fields
   // TODO check args for SQL Injection

   const pool = await poolP
   const [results, fields] = await pool.query(
      `SELECT ${sel}
       FROM ilias.usr_data AS ud
       WHERE login REGEXP '^[0-9]+$'
       LIMIT ${limit}
       OFFSET ${offset}
      `
   )
   const count = await getUserCount()
   return {
      total: count,
      offset, limit,
      data: results,
   }
}

async function getUserCount () {
   const pool = await poolP
   const [results, fields] = await pool.query(
      `SELECT COUNT(*)
       FROM ilias.usr_data AS ud
       WHERE login REGEXP '^[0-9]+$'`
   )
   return results[0]["COUNT(*)"]
}

async function getUserByLogin (login) {
   const sel = `usr_id, login, firstname, lastname, gender, email, institution, street, city, zipcode, country, department, active`
   // TODO user defined fields
   // TODO check args for SQL Injection

   const pool = await poolP
   const [results, fields] = await pool.query(
      `SELECT ${sel}
       FROM ilias.usr_data AS ud
       WHERE login = '${login}'
         AND login REGEXP '^[0-9]+$'`
   )
   return joinUDF(results[0])
}

async function getUserByUserId (userId) {
   const sel = `usr_id, login, firstname, lastname, gender, email, institution, street, city, zipcode, country, department, active`
   // TODO user defined fields
   // TODO check args for SQL Injection

   const pool = await poolP
   const [results, fields] = await pool.query(
      `SELECT ${sel}
       FROM ilias.usr_data AS ud
       WHERE usr_id = '${userId}'
         AND login REGEXP '^[0-9]+$'`
   )
   return joinUDF(results[0])
}

async function getUserDefinedFields () {
   const pool = await poolP
   const [results] = await pool.query(
      `SELECT ut.usr_id, ud.field_name, ut.value
        FROM ilias.udf_definition ud  
        JOIN ilias.udf_text ut ON ut.field_id = ud.field_id`
   )
   return results
}

async function getUserDefinedField (usr_id) {
   const pool = await poolP
   const [results] = await pool.query(
      `SELECT ut.usr_id, ud.field_name, ut.value
        FROM ilias.udf_definition ud  
        JOIN ilias.udf_text ut ON ut.field_id = ud.field_id
        WHERE ut.usr_id = '${usr_id}'
        `
   )
   return results
}

/////////////////////////////////////////////////////////////////////////

async function promiseDelay (ms) {
   return new Promise(resolve => setTimeout(resolve, ms))
}

async function joinUDF (user) {
   const fields = await getUserDefinedField(user.usr_id)
   for(const field of fields) {
      user[field.field_name] = field.value
   }
   return user
}