const mariadb = require("mariadb");
let dbConn;
let conPool;
// mariadb doc: https://github.com/MariaDB/mariadb-connector-nodejs/blob/master/documentation/promise-api.md

async function reconnect() {
    try {
        dbConn = await conPool.getConnection();
    } catch (e) {
        if (e.code === "ECONNREFUSED") {
            let err = new Error("Lost connection to the database");
            err.code = "ERR_DB_CONN_LOST";
            throw err;
        } else {
            throw e;
        }
    }
}

module.exports = async config => {
    conPool = mariadb.createPool({
        host: process.env.DB_HOST,
        user: process.env.DB_USER,
        password: process.env.DB_PASSWORD,
        port: process.env.DB_PORT,
        database: process.env.DATABASE,
        connectionLimit: 10
    });

    dbConn = await conPool.getConnection();
    return {
        async query(q, p) {
            let res;
            try {
                res = await dbConn.query(q, p);
            } catch (e) {
                if (e.code === "ER_CMD_CONNECTION_CLOSED") {
                    await reconnect();
                    await this.query(q, p);
                } else {
                    throw e;
                }
            }
            return res;
        }
    };
};