const mysql = require('mysql');
const config = require('../config.js');
const db_config = {
    host: config.dbHost,
    user: config.dbUsername,
    password: config.dbPassWord,
    database: config.dbName
};

class Database {
    constructor() {
        this.connection;
        this.handleDisconnect();
    }

    query(sql, args) {
        return new Promise((resolve, reject) => {
            this.connection.query(sql, args, (err, rows) => {
                if (err)
                    return reject(err);
                return resolve(rows);
            });
        });
    }
    close() {
        return new Promise((resolve, reject) => {
            this.connection.end(err => {
                if (err)
                    return reject(err);
                resolve();
            });
        });
    }

    handleDisconnect() {
        this.connection = mysql.createConnection(db_config); // Recreate the connection, since
        // the old one cannot be reused.

        this.connection.connect(function(err) { // The server is either down
            if (err) { // or restarting (takes a while sometimes).
                console.log('error when connecting to db:', err);
                setTimeout(this.handleDisconnect(), 2000); // We introduce a delay before attempting to reconnect,
            } // to avoid a hot loop, and to allow our node script to
        }); // process asynchronous requests in the meantime.
        // If you're also serving http, display a 503 error.
       this.connection.on('error', function(err) {
            console.log('db error', err);
            if (err.code === 'PROTOCOL_CONNECTION_LOST') { // Connection to the MySQL server is usually
                this.handleDisconnect(); // lost due to either server restart, or a
            } else { // connnection idle timeout (the wait_timeout
                throw err; // server variable configures this)
            }
        });
    }

}


module.exports = Database;