const mysql = require('mysql2');


class MysqlGateway {
    constructor () {
      this.connection = null;
    }

    createConnection (host, database, user, password, options) {
      let connectionInfo = {
        connectionLimit: options.connectionLimit || 500,
        acquireTimeout: options.connectTimeout || 10000,
        connectTimeout: options.connectTimeout || 10000,
        timeout: options.requestTimeout || 40000,
        host: host,
        database: database,
        user: user,
        password: password,
        multipleStatements: true,
        dateStrings: true
      };
      console.log('Connection info:' + JSON.stringify(connectionInfo));
      return this.connection = mysql.createPool(connectionInfo);
    }
    executeQuery (query) {
        return new Promise((resolve, reject) => {
          if (this.connection === null) {
            let error = new Error('Connection is null');
            error.code = 500;
            return reject(error);
          }
          this.connection.query(query, (err, res) => {
            if (err && err.code === 'ER_LOCK_DEADLOCK') {
              this.executeQuery(query).then(
                (res) => resolve(parseResult(res)),
                (error) => reject(error));
            } else if (err) {
              reject(err);
            } else {
              resolve(parseResult(res));
            }
          });
        });
      }
      async transaction (fields) {
        return await this.executeQuery('START TRANSACTION;');
      }

      add (table, fields) {
        let into = '';
        let values = '';
        for (let name in fields) {
          into += prepareName(name) + ',';
          values += prepareValue(fields[name]) + ',';
        }
        into = into.slice(0, -1);
        values = values.slice(0, -1);
        const query = `INSERT INTO ${table} (${Name}) VALUES (${Sallary});`;

        return this.executeQuery(query);
      }
    }