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 cleanup task at', dayjs().format('h:mma D MMM YYYY'));

	try {
    // Fetch events that haven't been visited in over 3 months
    const eventQuery = req.datastore.createQuery(req.types.event).filter('visited', '<', threeMonthsAgo);
		let oldEvents = (await req.datastore.runQuery(eventQuery))[0];

		if (oldEvents && oldEvents.length > 0) {
      let oldEventIds = oldEvents.map(e => e[req.datastore.KEY].name);
      console.log('Found', oldEventIds.length, 'events to remove');

      // Fetch availabilities linked to the events discovered
      let peopleDiscovered = 0;
      await Promise.all(oldEventIds.map(async (eventId) => {
        const peopleQuery = req.datastore.createQuery(req.types.person).filter('eventId', eventId);
    		let oldPeople = (await req.datastore.runQuery(peopleQuery))[0];

        if (oldPeople && oldPeople.length > 0) {
          peopleDiscovered += oldPeople.length;
          await req.datastore.delete(oldPeople.map(person => person[req.datastore.KEY]));
        }
      }));

      await req.datastore.delete(oldEvents.map(event => event[req.datastore.KEY]));

      console.log('Cleanup successful:', oldEventIds.length, 'events and', peopleDiscovered, 'people removed');

			res.sendStatus(200);
		} else {
      console.log('Found', 0, 'events to remove, ending cleanup');
			res.sendStatus(404);
		}
	} catch (e) {
		console.error(e);
		res.sendStatus(404);
	}
};