ChangeStreams

import scala.concurrent.{ ExecutionContext, Future }

import reactivemongo.api.ChangeStreams.FullDocumentStrategy

import reactivemongo.api.bson.BSONDocument
import reactivemongo.api.bson.collection.BSONCollection

def peekNext(
 coll: BSONCollection,
 strategy: FullDocumentStrategy)(
 implicit ec: ExecutionContext): Future[Option[BSONDocument]] =
 coll.watch[BSONDocument](fullDocumentStrategy = Some(strategy)).
   cursor.headOption

def doIt(coll: BSONCollection)(
 implicit ec: ExecutionContext): Future[Unit] = for {
   _ <- peekNext(coll, FullDocumentStrategy.Default)
   _ <- peekNext(coll, FullDocumentStrategy.UpdateLookup)
 } yield ()