#lang racket/base
;; Ground-event relay for os2.

(provide event-relay)
(require "os2.rkt")

(define event-relay
  (transition 'no-state
   (role 'relay-down (topic-publisher (cons (wild) (wild)) #:monitor? #t)
     #:state state
     #:topic t
     #:on-presence (match t
		     [(topic 'subscriber (cons (? evt? e) _) #f)
		      (printf "SUBSCRIBED ~v~n" e) (flush-output)
		      (transition state
			(at-meta-level
			 (role t (topic-subscriber (cons e (wild)))
			   #:state state
			   [msg
			    (printf "FIRED ~v -> ~v~n" e msg) (flush-output)
			    (transition state
			      (send-message msg))])))]
		     [_ state])
     #:on-absence (match t
		    [(topic 'subscriber (cons (? evt? e) _) #f)
		     (printf "UNSUBSCRIBED ~v~n" e) (flush-output)
		     (transition state
		       (at-meta-level (delete-role t)))]))))