1	import Base
2	
3	# Represents the owner lifecycle around lock, recovery, endpoint, and shutdown.
4	type State is Data:
5	  Starting{}
6	  Locked{}
7	  Recovered{}
8	  Serving{}
9	  Stopping{}
10	  EndpointRemoved{}
11	  Closed{}
12	  Failed{}
13	
14	# Represents one external result or requested lifecycle action.
15	type OwnerEvent is Data:
16	  AcquireLock{}
17	  RecoveryComplete{}
18	  PublishEndpoint{}
19	  BeginShutdown{}
20	  RemoveEndpoint{}
21	  ReleaseLock{}
22	  Failure{}
23	
24	# Returns the next legal state or rejects an out-of-order event.
25	type Decision is Data:
26	  Advance{state: State}
27	  Reject{}
28	
29	# Classifies durable failures before mapping them into wire statuses.
30	type FailureKind is Data:
31	  BusyFailure{}
32	  TimeoutFailure{}
33	  NotFoundFailure{}
34	  InvalidArgumentFailure{}
35	  AlreadyExistsFailure{}
36	  UnsupportedPlatformFailure{}
37	  ResourceLimitFailure{}
38	  CorruptionFailure{}
39	  IoFailure{}
40	  CommitUnknownFailure{}
41	
42	# Defines the typed response statuses available to coordinator clients.
43	type ReplyStatus is Data:
44	  SuccessStatus{}
45	  InvalidArgumentStatus{}
46	  AlreadyExistsStatus{}
47	  UnsupportedPlatformStatus{}
48	  NotFoundStatus{}
49	  BusyStatus{}
50	  TimeoutStatus{}
51	  ResourceLimitStatus{}
52	  CorruptionStatus{}
53	  IoStatus{}
54	  CommitUnknownStatus{}
55	
56	# Records whether the open path acquired, contended on, or failed to acquire the lock.
57	type LockOutcome is Data:
58	  LockAcquired{}
59	  LockBusy{}
60	  LockFailed{}
61	
62	# Records whether canonical endpoint inspection found a live candidate.
63	type EndpointOutcome is Data:
64	  EndpointPresent{}
65	  EndpointMissing{}
66	  EndpointFailed{}
67	
68	# Selects local ownership, remote use, or a typed open failure.
69	type OpenRole is Data:
70	  LocalOwner{}
71	  ExistingOwnerClient{}
72	  ReturnBusy{}
73	  PropagateOpenFailure{}
74	
75	# Chooses local ownership or an established endpoint from lock observations.
76	def open.role(lock: LockOutcome, endpoint: EndpointOutcome) -> OpenRole:
77	  match lock:
78	    case LockAcquired{}: LocalOwner{}
79	    case LockBusy{}:
80	      match endpoint:
81	        case EndpointPresent{}: ExistingOwnerClient{}
82	        case EndpointMissing{}: ReturnBusy{}
83	        case EndpointFailed{}: PropagateOpenFailure{}
84	    case LockFailed{}: PropagateOpenFailure{}
85	
86	def failure.status(kind: FailureKind) -> ReplyStatus:
87	  match kind:
88	    case BusyFailure{}: BusyStatus{}
89	    case TimeoutFailure{}: TimeoutStatus{}
90	    case NotFoundFailure{}: NotFoundStatus{}
91	    case InvalidArgumentFailure{}: InvalidArgumentStatus{}
92	    case AlreadyExistsFailure{}: AlreadyExistsStatus{}
93	    case UnsupportedPlatformFailure{}: UnsupportedPlatformStatus{}
94	    case ResourceLimitFailure{}: ResourceLimitStatus{}
95	    case CorruptionFailure{}: CorruptionStatus{}
96	    case IoFailure{}: IoStatus{}
97	    case CommitUnknownFailure{}: CommitUnknownStatus{}
98	
99	# Applies one lifecycle event without performing host effects.
100	def step(state: State, event: OwnerEvent) -> Decision:
101	  match state:
102	    case Starting{}:
103	      match event:
104	        case AcquireLock{}: Advance{Locked{}}
105	        case Failure{}: Advance{Failed{}}
106	        case _: Reject{}
107	    case Locked{}:
108	      match event:
109	        case RecoveryComplete{}: Advance{Recovered{}}
110	        case Failure{}: Advance{Failed{}}
111	        case _: Reject{}
112	    case Recovered{}:
113	      match event:
114	        case PublishEndpoint{}: Advance{Serving{}}
115	        case Failure{}: Advance{Failed{}}
116	        case _: Reject{}
117	    case Serving{}:
118	      match event:
119	        case BeginShutdown{}: Advance{Stopping{}}
120	        case Failure{}: Advance{Failed{}}
121	        case _: Reject{}
122	    case Stopping{}:
123	      match event:
124	        case RemoveEndpoint{}: Advance{EndpointRemoved{}}
125	        case Failure{}: Advance{Failed{}}
126	        case _: Reject{}
127	    case EndpointRemoved{}:
128	      match event:
129	        case ReleaseLock{}: Advance{Closed{}}
130	        case Failure{}: Advance{Failed{}}
131	        case _: Reject{}
132	    case Closed{}: Reject{}
133	    case Failed{}: Reject{}