http-response/sse-broadcast: default handler to identity

Message

Make the transform handler an optional leading positional defaulting to identity, so a hub that already carries pre-formatted SSE strings (the common case) needs no handler: (http-response/sse-broadcast hub on-connect: ...). Kept it positional (not a keyword) so existing positional-handler callers (vigil, sigil-web dev, sigil-web-demo) keep working unchanged.

Changed

 src/sigil/http/response.sgl | 43 +++++++++++++++++++++++++++++++------------
 1 file changed, 31 insertions(+), 12 deletions(-)

Diff

src/sigil/http/response.sglmodified

@@ -531,29 +531,48 @@

531

;; close function

532

close))))

533

+534

;; Look up a keyword's value in a flat keyword/value plist, else default.

+535

(define (sse-broadcast-kw-ref plist key default)

+536

(let loop ((p plist))

+537

(cond

+538

((or (null? p) (null? (cdr p))) default)

+539

((eq? (car p) key) (car (cdr p)))

+540

(else (loop (cdr (cdr p)))))))

+541

542

;;; Create an SSE response that broadcasts from a channel.

543

;;;

544

;;; Subscribes to a broadcast channel and sends events for each message.

−537

;;; The handler transforms messages into SSE event strings.

+545

;;; The handler transforms messages into SSE event strings; it is

+546

;;; optional and defaults to the identity function, so a hub that already

+547

;;; carries pre-formatted SSE strings (the common case) needs no handler.

548

;;;

549

;;; Parameters:

550

;;; broadcast: The broadcast channel to subscribe to

−541

;;; handler: (lambda (msg) ...) -> string or #f

−542

;;; Returns SSE event string to send, or #f to skip

+551

;;; handler: Optional (lambda (msg) ...) -> string or #f.

+552

;;; Returns SSE event string to send, or #f to skip.

+553

;;; Defaults to identity (send each message as-is).

554

;;; buffer-size: Subscriber buffer size (default: 32)

−544

;;; on-connect: Optional (lambda () ...) called on connect

−545

;;; Returns initial event string or #f

+555

;;; on-connect: Optional (lambda () ...) called on connect.

+556

;;; Returns initial event string or #f.

557

;;;

558

;;; Example:

559

;;; ```scheme

+560

;;; ;; Hub carries pre-formatted event strings — no handler needed:

+561

;;; (http-response/sse-broadcast hub on-connect: (lambda () (snapshot)))

+562

;;;

+563

;;; ;; Transform raw messages into SSE strings:

564

;;; (http-response/sse-broadcast chat-broadcast

−550

;;; (lambda (msg)

−551

;;; (sse-event "message" (json-encode msg))))

+565

;;; (lambda (msg) (sse-event "message" (json-encode msg))))

566

;;; ```

−553

(define (http-response/sse-broadcast broadcast handler

−554

(keys: (buffer-size 32)

−555

(on-connect #f)))

−556

(: any? procedure? (buffer-size: integer?) (on-connect: (maybe procedure?)) -> http-response?)

+567

(define (http-response/sse-broadcast broadcast . opts)

+568

;; `handler` is an optional leading positional (a procedure); anything

+569

;; after it (or all of `opts`, if the first isn't a procedure) is treated

+570

;; as buffer-size:/on-connect: keyword arguments.

+571

(let* ((has-handler (and (pair? opts) (procedure? (car opts))))

+572

(handler (if has-handler (car opts) (lambda (msg) msg)))

+573

(kwargs (if has-handler (cdr opts) opts))

+574

(buffer-size (sse-broadcast-kw-ref kwargs buffer-size: 32))

+575

(on-connect (sse-broadcast-kw-ref kwargs on-connect: #f)))

576

(http-response

577

status: HTTP-OK

578

headers: (dict

@@ -591,7 +610,7 @@

610

;; Write failed, clean up

611

(broadcast-unsubscribe broadcast sub)

612

;; Handler returned #f, skip and continue

−594

(loop))))))))))))

+613

(loop)))))))))))))

614

615

;;; Format a Server-Sent Event with event type and data.

616

;;;