; persist/event — an event is the unit of the log facet:
;   {:stream :seq :type :at :data}
; stream = which append-only stream, seq = 1-based position within it,
; type = event kind, at = caller-supplied timestamp (never a clock here:
; replay must stay pure), data = payload dict.

(define persist/event (fn (stream seq type at data) {:data data :type type :at at :stream stream :seq seq}))

(define persist/event-stream (fn (e) (get e :stream)))
(define persist/event-seq (fn (e) (get e :seq)))
(define persist/event-type (fn (e) (get e :type)))
(define persist/event-at (fn (e) (get e :at)))
(define persist/event-data (fn (e) (get e :data)))