(define (add ch-1 ch-2 res)
  (spawn
   (lambda ()
     (let lp ()
       (select
        (wrap (receive-rv ch-1)
              (lambda (v)
                (send res (+ v (receive ch-2)))))
        (wrap (receive-rv ch-2)
              (lambda (v)
                (send res (+ v (receive ch-1))))))
       (lp)))))

(define (copy in-ch out-ch1 out-ch2)
  (spawn
   (lambda ()
     (let lp ()
       (let ((v (receive in-ch)))
         (select
          (wrap (send-rv out-ch1 v)
                (lambda (ignore)
                  (send out-ch2 v)))
          (wrap (send-rv out-ch2 v)
                (lambda (ignore)
                  (send out-ch1 v)))))
       (lp)))))


(define (delay init in-ch out-ch)
  (spawn
   (lambda ()
     (let lp ((v init))
       (select
        (wrap (send-rv out-ch v)
              (lambda (ignore)
                (lp (receive in-ch))))
        (wrap (receive-rv in-ch)
              (lambda (next)
                (send out-ch v)
                (lp next))))))))

(define (make-fib-network)
  (let ((out-ch (make-channel))
        (c1 (make-channel))
        (c2 (make-channel))
        (c3 (make-channel))
        (c4 (make-channel))
        (c5 (make-channel)))
    (delay 0 c4 c5)
    (copy c2 c3 c4)
    (add c3 c5 c1)
    (copy c1 c2 out-ch)
    (send c1 1)
    out-ch))