/**
 *
 * @param {Request} request The incoming request
 * @param {Response} response The response to send back
 * @param {Express} app Express app instance
 * @param {Pool} pool MariaDB pool instance
 */
function handleIncoming(request, response, app, pool)
{

    let query = 'SELECT * FROM Exercise WHERE ExerciseID = ?';
    let parameters = [];

    if (!request.hasOwnProperty('uid') || typeof request.uid !== 'number')
    {
        query = 'SELECT * FROM Exercise ORDER BY RAND() LIMIT 1';
    } else parameters.push(request.uid);

    // Acquire database connection
    pool.getConnection()
        .then(conn => {
            conn.query(query, parameters)
                .then(rows => {
                    if (rows.length === 0)
                    {
                        response
                            .status(404)
                            .send(JSON.stringify({error: 'Exercise not found'}));
                    }
                    else
                    {
                        // Send back the data in the right format
                        let converted = rows.map(row => {
                            return {
                                name: row.Name,
                                description: row.Description,
                                muscleGroup: row.MuscleGroup,
                                imageUrl: row.ImageURL,
                                videoUrl: row.VideoURL
                            };
                        });

                        response
                            .status(200)
                            .send(JSON.stringify(converted));
                    }
                })
                .catch(error => {
                    console.log(error);
                    response
                        .status(500)
                        .send(JSON.stringify({error: 'Internal server error (Querying)'}));
                })
                .finally(() => {
                    conn.end();
                });
        })
        .catch(error => {
            console.log(error);
            response
                .status(500)
                .send(JSON.stringify({error: 'Internal server error (Connection)'}));
        });

}

// Export the function that registers the incoming request handlers
module.exports = function(app, pool) {
    app.post('/', (req, res) => handleIncoming(req, res, app, pool));
};