const util = require("util");
const mysql = require("mysql");
const metamgr = require("./metamgr");
const log = require("./log");

let pool = null;

function execQuery(sql, params) {
  if (!pool) {
    pool = mysql.createPool({
      host     : metamgr.getMysqlConf()['host'],
      user     : metamgr.getMysqlConf()['user'],
      password : metamgr.getMysqlConf()['passwd'],
      database : metamgr.getMysqlConf()['database'],
      stringifyObjects : true
    });
  }
  return new Promise((resolve) => {
    const ret = {
      err: null,
      rows: null,
    };

    pool.getConnection(function(err, conn) {
      if (err) {
        try {
          ret.err = err;
          resolve(ret);
          log.error(util.format(
            'sql:%s err:%s',
            sql, err
          ));
        } finally {
          conn.release();
        }
      } else {
        conn.query(sql, params, (err, rows) => {
          try {
            if (err) {
              ret.err = err;
              resolve(ret);
              log.error(util.format(
                'sql:%s err:%s',
                sql, err
              ));
            } else {
              ret.err = err;
              ret.rows = rows;
              resolve(ret);
            }
          } finally {
            conn.release();
          }
        });
      }
    });
  });
}

async function execQueryOne(sql, params) {
  const {err, rows} = await execQuery(sql, params);
  return {
    'err': err,
    'row': rows.length > 0 ? rows[0] : null
  };
}

async function execScript(sql, params) {
  const {err, rows} = await execQuery(sql, params);
  return err;
}

exports.execQuery = execQuery;
exports.execQueryOne = execQueryOne;
exports.execScript = execScript;