'use strict';

const fs = require('fs');
const helpers = require('./helpers');
const QueryBuilder = require('./QueryBuilder');

// Map config driver name to code class name
const dbDriverMap = new Map([
	['my', 'Mysql'],
	['mysql', 'Mysql'],
	['maria', 'Mysql'],
	['mariadb', 'Mysql'],
	['firebird', 'Firebird'],
	['postgresql', 'Pg'],
	['postgres', 'Pg'],
	['pg', 'Pg'],
	['sqlite3', 'Sqlite'],
	['sqlite', 'Sqlite'],
]);

/**
 * Class for connection management
 */
class NodeQuery {

	/**
	 * Constructor
	 *
	 * @param {object} config - connection paramaters
	 * @constructor
	 */
	constructor(config) {
		this.instance = null;

		if (config != null) {
			let drivername = dbDriverMap.get(config.driver);

			if (! drivername) {
				throw new Error(`Selected driver (${config.driver}) does not exist!`);
			}

			let driver = require(`./drivers/${drivername}`);
			let $adapter = require(`./adapters/${drivername}`);

			let adapter = new $adapter(config.connection);
			this.instance = new QueryBuilder(driver, adapter);
		}
	}

	/**
	 * Return an existing query builder instance
	 *
	 * @return {QueryBuilder} - The Query Builder object
	 */
	getQuery() {
		if (this.instance == null) {
			throw new Error('No Query Builder instance to return');
		}

		return this.instance;
	}
}

module.exports = (config => new NodeQuery(config));