#lang typed/syndicate/roles

(define-constructor (account balance)
  #:type-constructor AccountT
  #:with Account (AccountT Int)
  #:with AccountRequest (AccountT ★/t))

(define-constructor (deposit amount)
  #:type-constructor DepositT
  #:with Deposit (DepositT Int)
  #:with DepositRequest (DepositT ★/t))

(define-type-alias ds-type
  (U Account
     (Observe AccountRequest)
     (Observe (Observe AccountRequest))
     Deposit
     (Observe DepositRequest)
     (Observe (Observe DepositRequest))))

(spawn ds-type
  (print-role
  (start-facet account-manager
    (fields [balance Int 0])
    (assert (account (ref balance)))
    (on (asserted (deposit (bind amount Int)))
        (set! balance (+ (ref balance) amount))))))

(spawn ds-type
  (start-facet observer
    (fields)
    (on (asserted (account (bind amount Int)))
        (displayln amount))))