1	import Base
2	import ./change_tick.bend as Tick
3	import ./world.bend as W
4	import ./event_runtime.bend as Ev
5	import ./machine_stream.bend as St
6	import ./relation_commands.bend as A
7	import ./capabilities.bend as Cap
8	import ./inspector_stream_frame.bend as F
9	
10	# Declares a named transition-log projection. K and the resource lens take
11	# determine the stream; name is presentation metadata, not access validation.
12	type Declaration<S:Data,K:Data,V:Data,R:Type,-take:R -> R & St.Stream<V>> is Data:
13	  Declaration{name:String}
14	# Detached Data observation of a machine transition stream, not its owner.
15	type TransitionLog<S:Data,K:Data,V:Data> is Data:
16	  TransitionLog{stream:St.Stream<V>}
17	def joined(~S:Data,~K:Data,~V:Data,~C:Type,~R:Type,~E:Data,cursor:Maybe<&2,Tick.Tick>,namespace:U32,batches:List<&2,Ev.Batch<A.Notice<S,E>>>,positions:List<&2,Ev.Position>,nextReader:U32,tick:Nat,frameStart:Nat,boundary:Nat,capacity:Nat,dropped:Nat,observed:W.World<S,C,R,A.Notice<S,E>> & St.Stream<V>) -> F.Frame<S,C,R,E> & TransitionLog<S,K,V>:
18	  (world,stream)=observed
19	  (F.Frame{Ev.Runtime{world,namespace,batches,positions,nextReader,tick,frameStart,boundary,capacity,dropped},cursor},TransitionLog{stream})
20	# Observe the stream through the trusted resource lens and return the runtime
21	# in an Inspector frame. Preserve event batches, reader positions and cursor.
22	# The lens must return the resource owner with the intended stream observation.
23	def from_runtime(~S:Data,~K:Data,~V:Data,~C:Type,~R:Type,~E:Data,~take:R -> R & St.Stream<V>,cursor:Maybe<&2,Tick.Tick>,runtime:Ev.Runtime<S,C,R,A.Notice<S,E>>) -> F.Frame<S,C,R,E> & TransitionLog<S,K,V>:
24	  match runtime:
25	    case Ev.Runtime{world,namespace,batches,positions,nextReader,tick,frameStart,boundary,capacity,dropped}:joined(~S,~K,~V,~C,~R,~E,cursor,namespace,batches,positions,nextReader,tick,frameStart,boundary,capacity,dropped,W.observe_resource(~S,~C,~R,~A.Notice<S,E>,~St.Stream<V>,~take,world))
26	# Read the declared resource stream without executing a transition or advancing
27	# an event reader. Return the affine frame and its detached transition log.
28	def read(~S:Data,~K:Data,~V:Data,~C:Type,~R:Type,~E:Data,~take:R -> R & St.Stream<V>,frame:F.Frame<S,C,R,E>) -> F.Frame<S,C,R,E> & TransitionLog<S,K,V>:
29	  match frame:
30	    case F.Frame{runtime,cursor}:from_runtime(~S,~K,~V,~C,~R,~E,~take,cursor,runtime)
31	# Build a read capability using the declaration's typed resource lens. The
32	# declaration name does not select a different stream or enforce lens behavior.
33	def inspect(~S:Data,~K:Data,~V:Data,~C:Type,~R:Type,~E:Data,~take:R -> R & St.Stream<V>,~declaration:Declaration<S,K,V,R,take>) -> Cap.ValueRead<F.Frame<S,C,R,E>,TransitionLog<S,K,V>>:
34	  Cap.ValueRead{read(~S,~K,~V,~C,~R,~E,~take)}