const dayjs = require('dayjs');

module.exports = async (req, res) => {
  if (req.header('X-Appengine-Cron') === undefined) {
    return res.status(400).send('This task can only be run from a cron job');
  }

  const threeMonthsAgo = dayjs().subtract(3, 'month').unix();

  console.log(`Running orphan removal task at ${dayjs().format('h:mma D MMM YYYY')}`);

	try {
    // Fetch people that are older than 3 months
    const peopleQuery = req.datastore.createQuery(req.types.person).filter('created', '<', threeMonthsAgo);
		let oldPeople = (await req.datastore.runQuery(peopleQuery))[0];

		if (oldPeople && oldPeople.length > 0) {
      console.log(`Found ${oldPeople.length} people older than 3 months, checking for events`);

      // Fetch events linked to the people discovered
      let peopleWithoutEvents = 0;
      await Promise.all(oldPeople.map(async (person) => {
        let event = (await req.datastore.get(req.datastore.key([req.types.event, person.eventId])))[0];

        if (!event) {
          peopleWithoutEvents++;
          await req.datastore.delete(person[req.datastore.KEY]);
        }
      }));

      if (peopleWithoutEvents > 0) {
        console.log(`Orphan removal successful: ${oldEventIds.length} events and ${peopleDiscovered} people removed`);
        res.sendStatus(200);
      } else {
        console.log(`Found 0 people without events, ending orphan removal`);
  			res.sendStatus(404);
      }
		} else {
      console.log(`Found 0 people older than 3 months, ending orphan removal`);
			res.sendStatus(404);
		}
	} catch (e) {
		console.error(e);
		res.sendStatus(404);
	}
};