cleanVerifier.scala

/* It is common for the system to have more complex structures that house transactions, and these complex structures are what the system is dealing with
  It could be balance sheets as defined earlier, but lets pretend there are other structures used for Fraud detection as well...
  
  They are optionally there along with some arbitray metadata, and we need to run a verifier across the transactions inside these structures
  
  It would seem like a lot of very specific code is needed to get all this done; but in reality we already have all the combinators we need:
*/
def systemVerifier[S, Metadata](traversal: Traversal[S, Transaction], verifier: Pipe[IO, Transaction, Transaction]): Pipe[IO, (Option[S], Metadata), (Option[S], Metadata)] =
  _.flatMap(
    _1[(Option[S], Metadata), Option[S]]
      .composePrism(some)
      .composeTraversal(traversal)
      .modifyF(Stream.emit(_).through(verifier)))