1	import Base
2	import ./deferred_command.bend as Deferred
3	import ./trace_facts.bend as TraceFacts
4	import ./machine.bend as M
5	import ./transaction.bend as Tx
6	
7	# Bevy NextState::set_if_different preserves an existing forced same target.
8	# Equality is the same closed erased V comparator used by apply/conditions.
9	def forced_pending(~V:Data,same:Bool,prior:V,value:V) -> M.Pending<V>:
10	  match same:
11	    case True{}:M.Queued{prior,False{}}
12	    case False{}:M.Queued{value,True{}}
13	def conditional_pending(~V:Data,~same:V -> V -> Bool,pending:M.Pending<V>,+value:V) -> M.Pending<V>:
14	  match pending:
15	    case M.Queued{+prior,False{}}:forced_pending(~V,same(prior,value),prior,value)
16	    case _:M.Queued{value,True{}}
17	def conditional(~S:Data,~K:Data,~V:Data,~same:V -> V -> Bool,slot:M.Slot<S,K,V>,value:V) -> M.Slot<S,K,V>:
18	  match slot:
19	    case M.Missing{}:M.Missing{}
20	    case M.Present{current,pending,previous,changed}:M.Present{current,conditional_pending(~V,~same,pending,value),previous,changed}
21	def queue(~S:Data,~K:Data,~V:Data,~same:V -> V -> Bool,slot:M.Slot<S,K,V>,value:V,skipSame:Bool) -> M.Slot<S,K,V>:
22	  match skipSame:
23	    case False{}:M.queue(~S,~K,~V,slot,value,False{})
24	    case True{}:conditional(~S,~K,~V,~same,slot,value)
25	def write_taken(~S:Data,~K:Data,~V:Data,~W:Type,~E:Data,~put:W -> M.Slot<S,K,V> -> W,~same:V -> V -> Bool,pair:W & M.Slot<S,K,V>,undo:List<&1,(W -> W)>,commands:List<&1,Deferred.Command<W>>,events:List<&2,E>,trace:TraceFacts.State,value:V,skipSame:Bool) -> Tx.Tx<W,E>:
26	  match pair:
27	    case (world,+old):Tx.Tx{put(world,queue(~S,~K,~V,~same,old,value,skipSame)),(world => put(world,old)) <> undo,commands,events,trace}
28	def write(~S:Data,~K:Data,~V:Data,~W:Type,~E:Data,~take:W -> W & M.Slot<S,K,V>,~put:W -> M.Slot<S,K,V> -> W,~same:V -> V -> Bool,tx:Tx.Tx<W,E>,value:V,skipSame:Bool) -> Tx.Tx<W,E>:
29	  match tx:
30	    case Tx.Tx{world,undo,commands,events,trace}:write_taken(~S,~K,~V,~W,~E,~put,~same,take(world),undo,commands,events,trace,value,skipSame)
31	def next(~S:Data,~K:Data,~V:Data,~W:Type,~E:Data,~take:W -> W & M.Slot<S,K,V>,~put:W -> M.Slot<S,K,V> -> W,~same:V -> V -> Bool,tx:Tx.Tx<W,E>,request:M.QueueInput<V>) -> Tx.Tx<W,E>:
32	  match request:
33	    case M.Set{value,skipSame}:write(~S,~K,~V,~W,~E,~take,~put,~same,tx,value,skipSame)
34	    case M.Reset{}:M.reset_tx(~S,~K,~V,~W,~E,~take,~put,tx)
35	def declared_record(~W:Type,~E:Data,enabled:Bool,name:String,tx:Tx.Tx<W,E>) -> Tx.Tx<W,E>:
36	  match enabled:
37	    case False{}:tx
38	    case True{}:Tx.record(~W,~E,tx,TraceFacts.Fact{TraceFacts.NextStateValue{},name,TraceFacts.StageOperation{},None{},TraceFacts.OpaqueValue{},TraceFacts.OpaqueValue{},TraceFacts.Attempted{}})
39	def declared_named(~S:Data,~K:Data,~V:Data,~W:Type,~E:Data,~take:W -> W & M.Slot<S,K,V>,~put:W -> M.Slot<S,K,V> -> W,~same:V -> V -> Bool,name:String,request:M.QueueInput<V>,checked:Tx.Tx<W,E> & Bool) -> Tx.Tx<W,E>:
40	  match checked:
41	    case (tx,enabled):declared_record(~W,~E,enabled,name,next(~S,~K,~V,~W,~E,~take,~put,~same,tx,request))
42	def next_declared(~S:Data,~K:Data,~V:Data,~W:Type,~E:Data,~take:W -> W & M.Slot<S,K,V>,~put:W -> M.Slot<S,K,V> -> W,~same:V -> V -> Bool,family:M.Family<S,K,V,W,take,put>,tx:Tx.Tx<W,E>,request:M.QueueInput<V>) -> Tx.Tx<W,E>:
43	  match family:
44	    case M.Family{name}:declared_named(~S,~K,~V,~W,~E,~take,~put,~same,name,request,Tx.trace_enabled(~W,~E,tx))