import abc
import asyncio
from utils.value import AttributeChange


def fire_and_forget(coro):
	"""asyncio.create_task(), tolerant of there being no running event loop.
	An actor's observable attribute (e.g. Connectable.connected) can change
	as a side effect of the server's own final best-effort hardware-release
	cleanup (server/brewpi.py's `finally:` block - heater.close()/
	stirrer.activate(False)), which runs after the loop has already
	stopped. There's nobody left to notify at that point anyway, so this
	just drops the message instead of crashing the shutdown sequence."""
	try:
		return asyncio.create_task(coro)
	except RuntimeError:
		coro.close()
		return None


class ATask(AttributeChange):
	def __init__(self, interval):
		AttributeChange.__init__(self)
		self.interval = interval

	@abc.abstractmethod
	def on_process(self):
		pass


class TaskManager:
	def __init__(self):
		self.tasks = []

	def add(self, task: ATask):
		self.tasks.append(task)

	def start(self):
		funcs = []
		for task in self.tasks:
			funcs.append(task.on_process())

		return asyncio.gather(*funcs)