def reading

bendvy-ecs-core@0.1.0.4 · event_stream.bend:39

import Base
import bendvy-ecs-core@0.1.0.4/event_runtime.bend as Ev

39# Read ordered unread Data plus lag status using an existing position, or a
40# not-yet-activated position for id/tick. Returns stream metadata without advancing
41# its cursor. This helper does not validate an external reader token or World.
42def reading(~S:Data,~E:Data,+stream:Stream<S,E>,+id:U32,+tick:Nat) -> Stream<S,E> & Ev.Reading<E>:
43  match stream:
44    case Stream{+domain,+batches,+positions,+nextReader,+frameStart,+boundary,+capacity,+dropped}:read_position(~S,~E,Stream{domain,batches,positions,nextReader,frameStart,boundary,capacity,dropped},id,tick,Ev.lookup(positions,id))