;;; The C codec owns framing and protocol bytes. Scheme owns the readable view.
;;; Wire records have named fields, so optional fields can be added without
;;; changing positional call sites or the peer-visible protocol.

(define (dat:wire-message channel type payload)
  (if (not (and (integer? channel) (exact? channel) (>= channel 0)))
      (error 'out-of-range "wire channel must be a non-negative exact integer" channel))
  (if (not (and (integer? type) (exact? type) (>= type 0)))
      (error 'out-of-range "wire type must be a non-negative exact integer" type))
  (if (not (byte-vector? payload))
      (error 'wrong-type-arg "wire payload must be a bytevector" payload))
  (list 'dat:wire-message
        (cons 'channel channel)
        (cons 'type type)
        (cons 'payload payload)))

(define (dat:wire-message? value)
  (and (dat:record? value 'dat:wire-message)
       (integer? (dat:record-ref value 'channel #f))
       (integer? (dat:record-ref value 'type #f))
       (byte-vector? (dat:record-ref value 'payload #f))))

(define (dat:wire-frame->record bytes)
  (dat-wire->sexp bytes))

(define (dat:record->wire-frame record)
  (if (not (dat:wire-message? record))
      (error 'wrong-type-arg "expected a dat:wire-message record" record)
      (dat-sexp->wire record)))

(provide 'dat:wire)