// Require the core node modules.
var chalk = require( "chalk" );
var mysql = require( "mysql" ); // v2.11.1

// Define our connection to the MySQL database.
// --
// NOTE: In this demo, we are using a single connection.
var connection = mysql.createConnection({
	host : "127.0.0.1",
	user : "node",
	password: "node",
	database : "testing"
});


// ----------------------------------------------------------------------------------- //
// ----------------------------------------------------------------------------------- //


// When we submit a query before a connection is available, the driver will queue the
// query until the connection becomes available.
connection.on(
	"enqueue",
	function hanldeEvent() {

		console.log( chalk.bgYellow.white( "Waiting for connection slot." ) );

	}
);

// Run a few queries in serial. Since there is only one connection (we are not pooling),
// some of these queries will be enqueued before they are sent to the server.
for ( var i = 0 ; i < 5 ; i++ ) {

	connection.query(
		`
			SELECT
				COUNT( * ) AS userCount
			FROM
				user
		`,
		function handleResponse( error, records, fields ) {

			if ( error ) {

				console.log( chalk.bgRed.white( "Error:" ) );
				console.log( error );
				return;

			}

			console.log( chalk.bgGreen.white( "Count:", records[ 0 ].userCount ) );

		}
	);

} // END: For loop.

// Close the connection to the database so the Node.js process can close. Otherwise,
// the process will remain open until the database kills the connection.
// --
// NOTE: The .end() is a graceful operation on the connection - it will flush any
// queued queries before it sends the quit command to the MySQL server.
connection.end();