const { MongoClient } = require('mongodb');

(async function () {
	const client = new MongoClient('mongodb://localhost:27017', {
		maxPoolSize: 1,
	});

	await client.connect();

	const db = client.db('local');

	const _baseOplogSelector = {
		ns: new RegExp('^(?:rocketchat.)'),
		$or: [
			{ op: { $in: ['i', 'u', 'd'] } },
		],
	};

	const lastEntry = await db.collection('oplog.rs').findOne(_baseOplogSelector,
		{projection: {ts: 1}, sort: {$natural: -1}});

	const cursor = db.collection('oplog.rs').find({
		..._baseOplogSelector,
		ts: { '$gt' : lastEntry.ts }
	}, {
		tailable: true,
		awaitData: true,
	});

	cursor.addCursorFlag('oplogReplay', true);

	console.log('get doc');

	const doc = await cursor.next();

	console.log('doc ->', doc);

	client.close();
})();