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from __future__ import annotations
from dataclasses import dataclass, field
from itertools import count
from typing import Callable, List, Protocol
from automat import TypeMachineBuilder
# scaffolding; no state machines yet
@dataclass
class Request:
id: int = field(default_factory=count(1).__next__)
@dataclass
class RequestGetter:
cb: Callable[[Request], None] | None = None
def startGettingRequests(self, cb: Callable[[Request], None]) -> None:
self.cb = cb
@dataclass(repr=False)
class Task:
performer: TaskPerformer
request: Request
done: Callable[[Task, bool], None]
active: bool = True
number: int = field(default_factory=count(1000).__next__)
def __repr__(self) -> str:
return f"<task={self.number} request={self.request.id}>"
def complete(self, success: bool) -> None:
# Also a state machine, maybe?
print("complete", success)
self.performer.activeTasks.remove(self)
self.active = False
self.done(self, success)
def stop(self) -> None:
self.complete(False)
@dataclass
class TaskPerformer:
activeTasks: List[Task] = field(default_factory=list)
taskLimit: int = 3
def performTask(self, r: Request, done: Callable[[Task, bool], None]) -> Task:
self.activeTasks.append(it := Task(self, r, done))
return it
class ConnectionCoordinator(Protocol):
def start(self) -> None:
"kick off the whole process"
def requestReceived(self, r: Request) -> None:
"a task was received"
def taskComplete(self, task: Task, success: bool) -> None:
"task complete"
def atCapacity(self) -> None:
"we're at capacity stop handling requests"
def headroom(self) -> None:
"one of the tasks completed"
def cleanup(self) -> None:
"clean everything up"
@dataclass
class ConnectionState:
getter: RequestGetter
performer: TaskPerformer
allDone: Callable[[Task], None]
queue: List[Request] = field(default_factory=list)
def buildMachine() -> Callable[[ConnectionState], ConnectionCoordinator]:
builder = TypeMachineBuilder(ConnectionCoordinator, ConnectionState)
Initial = builder.state("Initial")
Requested = builder.state("Requested")
AtCapacity = builder.state("AtCapacity")
CleaningUp = builder.state("CleaningUp")
Requested.upon(ConnectionCoordinator.atCapacity).to(AtCapacity).returns(None)
Requested.upon(ConnectionCoordinator.headroom).loop().returns(None)
CleaningUp.upon(ConnectionCoordinator.headroom).loop().returns(None)
CleaningUp.upon(ConnectionCoordinator.cleanup).loop().returns(None)
@Initial.upon(ConnectionCoordinator.start).to(Requested)
def startup(coord: ConnectionCoordinator, core: ConnectionState) -> None:
core.getter.startGettingRequests(coord.requestReceived)
@AtCapacity.upon(ConnectionCoordinator.requestReceived).loop()
def requestReceived(
coord: ConnectionCoordinator, core: ConnectionState, r: Request
) -> None:
print("buffering request", r)
core.queue.append(r)
@AtCapacity.upon(ConnectionCoordinator.headroom).to(Requested)
def headroom(coord: ConnectionCoordinator, core: ConnectionState) -> None:
"nothing to do, just transition to Requested state"
unhandledRequest = core.queue.pop()
print("dequeueing", unhandledRequest)
coord.requestReceived(unhandledRequest)
@Requested.upon(ConnectionCoordinator.requestReceived).loop()
def requestedRequest(
coord: ConnectionCoordinator, core: ConnectionState, r: Request
) -> None:
print("immediately handling request", r)
core.performer.performTask(r, coord.taskComplete)
if len(core.performer.activeTasks) >= core.performer.taskLimit:
coord.atCapacity()
@Initial.upon(ConnectionCoordinator.taskComplete).loop()
@Requested.upon(ConnectionCoordinator.taskComplete).loop()
@AtCapacity.upon(ConnectionCoordinator.taskComplete).loop()
@CleaningUp.upon(ConnectionCoordinator.taskComplete).loop()
def taskComplete(
c: ConnectionCoordinator, s: ConnectionState, task: Task, success: bool
) -> None:
if success:
c.cleanup()
s.allDone(task)
else:
c.headroom()
@Requested.upon(ConnectionCoordinator.cleanup).to(CleaningUp)
@AtCapacity.upon(ConnectionCoordinator.cleanup).to(CleaningUp)
def cleanup(coord: ConnectionCoordinator, core: ConnectionState):
# We *don't* want to recurse in here; stopping tasks will cause
# taskComplete!
while core.performer.activeTasks:
core.performer.activeTasks[-1].stop()
return builder.build()
ConnectionMachine = buildMachine()
def begin(
r: RequestGetter, t: TaskPerformer, done: Callable[[Task], None]
) -> ConnectionCoordinator:
machine = ConnectionMachine(ConnectionState(r, t, done))
machine.start()
return machine
def story() -> None:
rget = RequestGetter()
tper = TaskPerformer()
def yay(t: Task) -> None:
print("yay")
m = begin(rget, tper, yay)
cb = rget.cb
assert cb is not None
cb(Request())
cb(Request())
cb(Request())
cb(Request())
cb(Request())
cb(Request())
cb(Request())
print([each for each in tper.activeTasks])
sc: ConnectionState = m.__automat_core__ # type:ignore
print(sc.queue)
tper.activeTasks[0].complete(False)
tper.activeTasks[0].complete(False)
print([each for each in tper.activeTasks])
print(sc.queue)
tper.activeTasks[0].complete(True)
print([each for each in tper.activeTasks])
if __name__ == "__main__":
story()
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