enum SagaFilter

@error data Boom { m: str }

service Bank {
  @public @idempotent rpc hold(n: u64) -> u64
  @public @idempotent rpc unhold(n: u64) -> () | Boom
  @public @idempotent rpc refuse(n: u64) -> u64 | Boom
}

impl Bank {
  rpc hold(n) => n
  rpc unhold(n) { fail Boom{ m: "bank is down" } }
  rpc refuse(n) { fail Boom{ m: "no" } }
}

// the second step fails and its compensation never succeeds: the saga becomes stuck
saga pay(n: u64) -> u64 {
  Bank.hold(n)   undo h => Bank.unhold(h)
  -> Bank.refuse(n)
}

fn main() io, net, time, db {
  let _ = pay(9)
  print("stuck {std.saga.list(.Stuck).len()}, active {std.saga.list(.Active).len()}")
}

stuck 1, active 0