kw on

ActorMember = { Attr } ( "var" Ident ":" Type "=" Expr | "dep" Ident ":" Type
            | "msg" Ident "(" [ Params ] ")" [ "->" Type ] Block
            | "on" ( "activate" | "passivate" ) Block ) ;

PStep       = ( "respond" Expr | Expr ) [ "on" Ident ] [ "durable" | "best_effort" ] ;

Suffix      = "within" Binary | "retry" Binary [ "on" Type ] [ "backoff" Binary ] ;

@idle(ACCOUNT_IDLE)
actor Account sharded by id: AccountId {
  var balance: Money = Money.zero()
  @transient var hits: u64 = 0
  on activate { log.debug("account {id} up") }
  msg deposit(x: Money) { balance += x }
  msg balance() -> Money { balance }
}

Account(id).deposit(amount)

pipeline uploadPhoto(img: Image) -> PhotoId {
  validate
  -> Store.put(it)              on storage
  -> respond it.id
  -> resize(it, THUMB_SIZES)    on gpu
  -> moderate                   on ml  durable
  -> SearchIndex.add(it)
} on_error(e, step) { Dlq.push(e, step) }