I am a working on a personal project, and am still learning. I am building a REST API backend app with 3 models (User, Event, & City).

For a GET route I want to be able to

1. list All events
2. filter events by user
3. filter events by city

I am uncertain what would be considered best practice for routes 2 & 3.

Currently, I have it routed through api/v1/events and the user has an option to add either the user_id OR the city_id to the params, and then my controller will pass the request to the correct service. I feel that there is a lot of room for user error here and want to improve it. I can think of a few different pathways forward but wanted to ask if there is a best practice for this.

Side note: to get the events filtered by users, I have to do a query to my User db, not the Event db. I am not sure if it looks wrong here and if I should move it to the User controller.

I have looked at a lot of API GitHub examples while building this but have not come across this specific situation. Thank you very much for your thoughts and insight.

My Controller func:

async function listAllEvents(req: express.Request, res: express.Response) {
  logger.debug(`Entering GET All CONTROLLER - events/ endpoint.`);
  type ReturnValue = User | Event[];
  let events: ReturnValue = [];
  if (req.query.cityId) {
    let cityId = req.query.cityId as string;
    events = await EventService.filterEventsByCityId(cityId);
  } else if (req.query.userId) {
    let userId = req.query.userId as string;
    events = await EventService.filterEventsByUserId(userId);
  } else {
    events = await EventService.listAllEvents();
  }
  try {
    if (!events) {
      res.status(404).json({ error: `No events found` });
      return;
    } else {
      res.json(events);
    }
  } catch (err) {
    logger.error(err);
    res.status(500).send(err);
  }
}