1	import Base
2	import ./change_tick.bend as Tick
3	import ./trace_facts.bend as Facts
4	
5	# Detached copied facts. No World, registration, cursor or stream owner is held.
6	# Copied system identity for presentation: namespace/id and optional name.
7	# It is metadata, not a registration owner or capability for invoking that system.
8	type Identity is Data:
9	  Identity{namespace:U32,id:U32,name:Maybe<&2,String>}
10	# Completion status of one executed system, retaining its detached Data error.
11	type Status<Error:Data> is Data:
12	  SystemOk{}
13	  SystemError{error:Error}
14	# Schedule-level completion distinguishes failure, admission rejection and missing
15	# execution from success; it is not a replacement for the retained App run result.
16	type Completion<Error:Data> is Data:
17	  EndOk{}
18	  EndFailed{error:Error}
19	  EndRejected{}
20	  EndMissing{}
21	# Ordered copied execution facts: schedule/phase boundaries, systems, operations
22	# and admission outcomes. Facts describe the actual run; they grant no mutable
23	# World access and do not imply that a failed transaction committed its operations.
24	type TraceEvent<Error:Data> is Data:
25	  ScheduleStarted{namespace:U32,name:String}
26	  PhaseEntered{name:String}
27	  SystemCompleted{identity:Identity,before:Tick.Tick,after:Tick.Tick,status:Status<Error>}
28	  OperationObserved{identity:Identity,fact:Facts.Fact}
29	  BarrierOperationObserved{fact:Facts.Fact}
30	  ExecutionOperationObserved{fact:Facts.Fact}
31	  SystemSkipped{id:U32}
32	  DeferredApplied{}
33	  ScheduleEnded{outcome:Completion<Error>}
34	  ScheduleAdmissionRefused{namespace:U32,name:String,outcome:Completion<Error>}
35	# Detached delivery value returned after execution. Disabled differs from an
36	# enabled Ready batch with no events. No live reader or stream retention is held;
37	# keeping or dropping a copied batch does not acknowledge an ECS event reader.
38	type Batch<Error:Data> is Data:
39	  Disabled{}
40	  Ready{events:List<&2,TraceEvent<Error>>}
41	
42	# Each subscription is its actual affine state owner, not a copied callback.
43	# The erased reusable step is supplied as a top-level definition.
44	type Subscriber<State:Type,Error:Data,-step:State -> TraceEvent<Error> -> State> is Type:
45	  Subscriber{state:State}
46	# Wrap the supplied actual State owner with a reusable erased step definition.
47	# This creates a local subscriber, not an ECS registration or automatic callback.
48	def subscribe(~State:Type,~Error:Data,~step:State -> TraceEvent<Error> -> State,state:State) -> Subscriber<State,Error,step>:
49	  Subscriber{state}
50	# Consume the subscriber and return its actual State for reuse or explicit
51	# disposal. No implicit user cleanup/destructor callback is invoked.
52	def unsubscribe(~State:Type,~Error:Data,~step:State -> TraceEvent<Error> -> State,value:Subscriber<State,Error,step>) -> State:
53	  match value:
54	    case Subscriber{state}:state
55	# Replace subscription state and return the displaced actual owner separately.
56	# Neither owner is copied or silently restored into ECS storage.
57	def reset(~State:Type,~Error:Data,~step:State -> TraceEvent<Error> -> State,value:Subscriber<State,Error,step>,incoming:State) -> Subscriber<State,Error,step> & State:
58	  match value:
59	    case Subscriber{state}:(Subscriber{incoming},state)
60	def delivered(~State:Type,~Error:Data,~step:State -> TraceEvent<Error> -> State,events:List<&2,TraceEvent<Error>>,state:State) -> State:
61	  match events:
62	    case []:state
63	    case event <> rest:delivered(~State,~Error,~step,rest,step(state,event))
64	# Thread subscriber State through Ready events in list order; Disabled returns
65	# the subscriber unchanged. Delivery is explicitly called after the ECS run.
66	# Any external printing/file IO performed by a consumer is outside ECS rollback,
67	# not an in-transaction observer. See examples/scheduled-health/application.bend.
68	def deliver(~State:Type,~Error:Data,~step:State -> TraceEvent<Error> -> State,value:Subscriber<State,Error,step>,batch:Batch<Error>) -> Subscriber<State,Error,step>:
69	  match value batch:
70	    case subscriber Disabled{}:subscriber
71	    case Subscriber{state} Ready{events}:Subscriber{delivered(~State,~Error,~step,events,state)}
72	
73	# Generic owner composition has no arity or subscriber-count bound. Order is
74	# left then right; each reusable delivery function can itself be another pair.
75	# Deliver the same detached batch to two actual owners, left then right, returning
76	# both results. Compose this adapter recursively for additional subscribers; this
77	# is owner composition, not a global subscription registry.
78	def both(~Left:Type,~Right:Type,~Error:Data,~left:Left -> Batch<Error> -> Left,~right:Right -> Batch<Error> -> Right,value:Left & Right,+batch:Batch<Error>) -> Left & Right:
79	  match value:
80	    case (first,second):(left(first,batch),right(second,batch))