"""Debounce helper."""
import asyncio
from logging import Logger
from typing import Any, Awaitable, Callable, Optional

from homeassistant.core import HomeAssistant, callback


class Debouncer:
    """Class to rate limit calls to a specific command."""

    def __init__(
        self,
        hass: HomeAssistant,
        logger: Logger,
        cooldown: float,
        immediate: bool,
        function: Optional[Callable[..., Awaitable[Any]]] = None,
    ):
        """Initialize debounce.

        immediate: indicate if the function needs to be called right away and
                   wait 0.3s until executing next invocation.
        function: optional and can be instantiated later.
        """
        self.hass = hass
        self.logger = logger
        self.function = function
        self.cooldown = cooldown
        self.immediate = immediate
        self._timer_task: Optional[asyncio.TimerHandle] = None
        self._execute_at_end_of_timer: bool = False

    async def async_call(self) -> None:
        """Call the function."""
        assert self.function is not None

        if self._timer_task:
            if not self._execute_at_end_of_timer:
                self._execute_at_end_of_timer = True

            return

        if self.immediate:
            await self.hass.async_add_job(self.function)  # type: ignore
        else:
            self._execute_at_end_of_timer = True

        self._timer_task = self.hass.loop.call_later(
            self.cooldown,
            lambda: self.hass.async_create_task(self._handle_timer_finish()),
        )

    async def _handle_timer_finish(self) -> None:
        """Handle a finished timer."""
        assert self.function is not None

        self._timer_task = None

        if not self._execute_at_end_of_timer:
            return

        self._execute_at_end_of_timer = False

        try:
            await self.hass.async_add_job(self.function)  # type: ignore
        except Exception:  # pylint: disable=broad-except
            self.logger.exception("Unexpected exception from %s", self.function)

    @callback
    def async_cancel(self) -> None:
        """Cancel any scheduled call."""
        if self._timer_task:
            self._timer_task.cancel()
            self._timer_task = None

        self._execute_at_end_of_timer = False
