# Copyright 2023 (c) Anna Schumaker.
"""Functions for configuring a callback at a specific time."""
import datetime
import math
from gi.repository import GLib

_GSOURCE_MAPPING = dict()
_NEXT_ALARM_ID = 1


def _calc_seconds(time: datetime.time) -> int:
    """Calculate the number of seconds until the given time."""
    now = datetime.datetime.now()
    then = datetime.datetime.combine(now.date(), time)

    if now >= then:
        then += datetime.timedelta(days=1)

    return math.ceil((then - now).total_seconds())


def __set_alarm(time: datetime.time, func: callable, alarm_id: int) -> None:
    gsrcid = GLib.timeout_add_seconds(_calc_seconds(time), _do_alarm,
                                      time, func, alarm_id)
    _GSOURCE_MAPPING[alarm_id] = gsrcid
    return alarm_id


def _do_alarm(time: datetime.time, func: callable, alarm_id: int) -> bool:
    """Run an alarm callback."""
    func()
    __set_alarm(time, func, alarm_id)
    return GLib.SOURCE_REMOVE


def set_alarm(time: datetime.time, func: callable) -> int:
    """Register a callback to be called at a specific time."""
    global _NEXT_ALARM_ID

    res = __set_alarm(time, func, _NEXT_ALARM_ID)
    _NEXT_ALARM_ID += 1
    return res


def cancel_alarm(alarm_id: int) -> None:
    """Cancel an alarm."""
    GLib.source_remove(_GSOURCE_MAPPING[alarm_id])
    del _GSOURCE_MAPPING[alarm_id]