1	import Base
2	import ./world.bend as W
3	
4	# Legacy independent affine readers for the append-only event log.
5	# Registered bounded retention/lag/skip/disposal use event-runtime.bend.
6	# Affine payload streams use the separate owned-event APIs.
7	# Legacy independent reader for one World's append-only Data event log.
8	# Owns a namespace and list offset, not a registered retention lease. Use
9	# event-runtime or typed family readers for bounded retention/lag/skip/disposal.
10	type Reader<S: Data> is Type:
11	  Reader{namespace: U32,offset: Nat}
12	# Read returns World, advanced reader and detached unread Data events;
13	# ForeignReader returns World and the original reader without reading the log.
14	# Neither result carries affine event payload ownership.
15	type Observed<S: Data,C: Type,R: Type,E: Data> is Type:
16	  Read{world: W.World<S,C,R,E>,reader: Reader<S>,events: List<&2,E>}
17	  ForeignReader{world: W.World<S,C,R,E>,reader: Reader<S>}
18	
19	def create_join(~S: Data,~C: Type,~R: Type,~E: Data,named: W.World<S,C,R,E> & U32) -> W.World<S,C,R,E> & Reader<S>:
20	  (world,namespace) = named
21	  (world,Reader{namespace,0n})
22	
23	# Create an independent append-only reader at offset zero, returning World.
24	# Existing events are initially unread. This creates no system registration or
25	# bounded-retention lease; raw Reader construction remains trusted setup.
26	def create(~S: Data,~C: Type,~R: Type,~E: Data,world: W.World<S,C,R,E>) -> W.World<S,C,R,E> & Reader<S>:
27	  create_join(~S,~C,~R,~E,W.namespace(~S,~C,~R,~E,world))
28	
29	def read_events(~S: Data,~C: Type,~R: Type,~E: Data,+namespace: U32,+offset: Nat,observed: W.World<S,C,R,E> & List<&2,E>) -> Observed<S,C,R,E>:
30	  (world,+events) = observed
31	  Read{world,Reader{namespace,List.length(&2,E,events)},List.drop(&2,E,events,offset)}
32	
33	def read_checked(~S: Data,~C: Type,~R: Type,~E: Data,allowed: Bool,world: W.World<S,C,R,E>,reader: Reader<S>) -> Observed<S,C,R,E>:
34	  match allowed reader:
35	    case False{} reader: ForeignReader{world,reader}
36	    case True{} Reader{+namespace,+offset}: read_events(~S,~C,~R,~E,namespace,offset,W.events_view(~S,~C,~R,~E,world))
37	
38	def read_named(~S: Data,~C: Type,~R: Type,~E: Data,named: W.World<S,C,R,E> & U32,reader: Reader<S>) -> Observed<S,C,R,E>:
39	  match named reader:
40	    case (world,actual) Reader{+namespace,+offset}: read_checked(~S,~C,~R,~E,U32.is_eq(actual,namespace),world,Reader{namespace,offset})
41	
42	# Read the unread append-only suffix and return the reader at current log
43	# length, preserving event order. Namespace mismatch returns ForeignReader
44	# without accessing events. No registered lifecycle cursor or stream retention
45	# state is advanced. This legacy path has no lag/refusal protocol for log reset.
46	# Example: examples/user-simulation/driver.bend; bounded readers: event-runtime.
47	def read(~S: Data,~C: Type,~R: Type,~E: Data,world: W.World<S,C,R,E>,reader: Reader<S>) -> Observed<S,C,R,E>:
48	  read_named(~S,~C,~R,~E,W.namespace(~S,~C,~R,~E,world),reader)