1	import Base
2	import ../ByteMemTable.bend as ByteMemTable
3	import ../ByteWal.bend as ByteWal
4	
5	# Carries the state for Decision.
6	type Decision is Data:
7	  NeedSst{}
8	  Missing{}
9	  Found{value_bytes: U32}
10	
11	# Handles delta.
12	def delta(probe: ByteMemTable.LengthProbe) -> Decision:
13	  match probe:
14	    case ByteMemTable.LengthAbsent{}: NeedSst{}
15	    case ByteMemTable.LengthDeleted{}: Missing{}
16	    case ByteMemTable.LengthPresent{value_bytes}: Found{value_bytes}
17	
18	# Handles persisted.
19	def persisted(metadata: ByteWal.ValueMetadata) -> Decision:
20	  match metadata:
21	    case ByteWal.ValueAbsent{}: Missing{}
22	    case ByteWal.ValueDeleted{}: Missing{}
23	    case ByteWal.ValuePresent{value_bytes}: Found{value_bytes}
24	
25	# Handles result.
26	def result(
27	  delta: ByteMemTable.LengthProbe,
28	  persisted_metadata: ByteWal.ValueMetadata
29	) -> Decision:
30	  match delta:
31	    case ByteMemTable.LengthAbsent{}: persisted(persisted_metadata)
32	    case ByteMemTable.LengthDeleted{}: Missing{}
33	    case ByteMemTable.LengthPresent{value_bytes}: Found{value_bytes}