syndicate-2017/racket/syndicate/examples/chat-simplified-internals.rkt

81 lines
3.1 KiB
Racket

#lang syndicate
;; The chat server, using a proxy abstracting over details of the TCP
;; driver's protocol.
(require (only-in racket/string string-trim))
(require "../drivers/tcp.rkt")
(require "../demand-matcher.rkt")
(struct tcp-remote-open (id) #:prefab)
(struct tcp-local-open (id) #:prefab)
(struct tcp-incoming-data (id bytes) #:prefab)
(struct tcp-outgoing-data (id bytes) #:prefab)
(struct says (who what) #:prefab)
(struct present (who) #:prefab)
(define (tcp-proxy-process them us)
(define id (seal (list them us)))
(spawn (lambda (e s)
(match e
[(message (tcp-channel _ _ bs))
(transition s (message (tcp-incoming-data id bs)))]
[(message (tcp-outgoing-data _ bs))
(transition s (message (tcp-channel us them bs)))]
[(? patch/removed?)
(quit)]
[_ #f]))
(void)
(patch-seq (sub (tcp-channel them us ?))
(sub (advertise (tcp-channel them us ?)))
(pub (tcp-channel us them ?))
(sub (tcp-outgoing-data id ?))
(assert (tcp-remote-open id))
(sub (tcp-local-open id)))))
(define (spawn-session id)
(define user (gensym 'user))
(define (send-to-remote fmt . vs)
(message (tcp-outgoing-data id (string->bytes/utf-8 (apply format fmt vs)))))
(define (say who fmt . vs)
(unless (equal? who user) (send-to-remote "~a ~a\n" who (apply format fmt vs))))
(list (send-to-remote "Welcome, ~a.\n" user)
(spawn/stateless
(lambda (e)
(match e
[(message (tcp-incoming-data _ bs))
(message (says user (string-trim (bytes->string/utf-8 bs))))]
[(message (says who what))
(say who "says: ~a" what)]
[(? patch? p)
(if (patch/removed? (patch-project p (tcp-remote-open id)))
(quit)
(let-values (((arrived departed) (patch-project/set/single p (present (?!)))))
(list (for/list [(who arrived)] (say who "arrived."))
(for/list [(who departed)] (say who "departed.")))))]
[#f #f]))
(patch-seq
(sub (says ? ?)) ;; read actual chat messages
(sub (present ?)) ;; observe peer presence
(assert (present user)) ;; advertise our presence
(sub (tcp-incoming-data id ?)) ;; read from remote client
(sub (tcp-remote-open id)) ;; monitor remote client
(assert (tcp-local-open id)) ;; indicate our end of the connection is up
))))
(spawn-tcp-driver)
(spawn-demand-matcher (advertise (tcp-channel (?!) (?! (tcp-listener 5999)) ?))
(observe (tcp-channel (?!) (?! (tcp-listener 5999)) ?))
tcp-proxy-process)
(spawn (lambda (e s)
(if (patch? e)
(transition s
(for/list [(id (project-assertions (patch-added e)
(tcp-remote-open (?!))))]
(spawn-session id)))
#f))
(void)
(sub (tcp-remote-open ?)))