kmk-paintbrush/kmk/scheduler.py

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'''
Here we're abusing _asyncios TaskQueue to implement a very simple priority
queue task scheduler.
Despite documentation, Circuitpython doesn't usually ship with a min-heap
module; it does however implement a pairing-heap for `TaskQueue` in native code.
'''
try:
from typing import Callable
except ImportError:
pass
from supervisor import ticks_ms
from _asyncio import Task, TaskQueue
from kmk.kmktime import ticks_add, ticks_diff
_task_queue = TaskQueue()
class PeriodicTaskMeta:
def __init__(self, func: Callable[[None], None], period: int) -> None:
self._task = Task(self.call)
self._coro = func
self.period = period
def call(self) -> None:
self._coro()
after_ms = ticks_add(self._task.ph_key, self.period)
_task_queue.push_sorted(self._task, after_ms)
def create_task(
func: Callable[[None], None],
*,
after_ms: int = 0,
period_ms: int = 0,
) -> [Task, PeriodicTaskMeta]:
if period_ms:
r = PeriodicTaskMeta(func, period_ms)
t = r._task
else:
t = r = Task(func)
if after_ms:
after_ms = ticks_add(ticks_ms(), after_ms)
_task_queue.push_sorted(t, after_ms)
else:
_task_queue.push_head(t)
return r
def get_due_task() -> [Callable, None]:
while True:
t = _task_queue.peek()
if not t or ticks_diff(t.ph_key, ticks_ms()) > 0:
break
_task_queue.pop_head()
yield t.coro
def cancel_task(t: [Task, PeriodicTaskMeta]) -> None:
if isinstance(t, PeriodicTaskMeta):
t = t._task
_task_queue.remove(t)