"""Support for functionality to keep track of the sun."""
from datetime import timedelta
import logging

from homeassistant.const import (
    CONF_ELEVATION,
    EVENT_CORE_CONFIG_UPDATE,
    SUN_EVENT_SUNRISE,
    SUN_EVENT_SUNSET,
)
from homeassistant.core import callback
from homeassistant.helpers import event
from homeassistant.helpers.entity import Entity
from homeassistant.helpers.sun import (
    get_astral_location,
    get_location_astral_event_next,
)
from homeassistant.util import dt as dt_util

# mypy: allow-untyped-calls, allow-untyped-defs, no-check-untyped-defs

_LOGGER = logging.getLogger(__name__)

DOMAIN = "sun"

ENTITY_ID = "sun.sun"

STATE_ABOVE_HORIZON = "above_horizon"
STATE_BELOW_HORIZON = "below_horizon"

STATE_ATTR_AZIMUTH = "azimuth"
STATE_ATTR_ELEVATION = "elevation"
STATE_ATTR_RISING = "rising"
STATE_ATTR_NEXT_DAWN = "next_dawn"
STATE_ATTR_NEXT_DUSK = "next_dusk"
STATE_ATTR_NEXT_MIDNIGHT = "next_midnight"
STATE_ATTR_NEXT_NOON = "next_noon"
STATE_ATTR_NEXT_RISING = "next_rising"
STATE_ATTR_NEXT_SETTING = "next_setting"

# The algorithm used here is somewhat complicated. It aims to cut down
# the number of sensor updates over the day. It's documented best in
# the PR for the change, see the Discussion section of:
# https://github.com/home-assistant/home-assistant/pull/23832


# As documented in wikipedia: https://en.wikipedia.org/wiki/Twilight
# sun is:
# < -18° of horizon - all stars visible
PHASE_NIGHT = "night"
# 18°-12° - some stars not visible
PHASE_ASTRONOMICAL_TWILIGHT = "astronomical_twilight"
# 12°-6° - horizon visible
PHASE_NAUTICAL_TWILIGHT = "nautical_twilight"
# 6°-0° - objects visible
PHASE_TWILIGHT = "twilight"
# 0°-10° above horizon, sun low on horizon
PHASE_SMALL_DAY = "small_day"
# > 10° above horizon
PHASE_DAY = "day"

# 4 mins is one degree of arc change of the sun on its circle.
# During the night and the middle of the day we don't update
# that much since it's not important.
_PHASE_UPDATES = {
    PHASE_NIGHT: timedelta(minutes=4 * 5),
    PHASE_ASTRONOMICAL_TWILIGHT: timedelta(minutes=4 * 2),
    PHASE_NAUTICAL_TWILIGHT: timedelta(minutes=4 * 2),
    PHASE_TWILIGHT: timedelta(minutes=4),
    PHASE_SMALL_DAY: timedelta(minutes=2),
    PHASE_DAY: timedelta(minutes=4),
}


async def async_setup(hass, config):
    """Track the state of the sun."""
    if config.get(CONF_ELEVATION) is not None:
        _LOGGER.warning(
            "Elevation is now configured in Home Assistant core. "
            "See https://www.home-assistant.io/docs/configuration/basic/"
        )
    Sun(hass)
    return True


class Sun(Entity):
    """Representation of the Sun."""

    entity_id = ENTITY_ID

    def __init__(self, hass):
        """Initialize the sun."""
        self.hass = hass
        self.location = None
        self._state = self.next_rising = self.next_setting = None
        self.next_dawn = self.next_dusk = None
        self.next_midnight = self.next_noon = None
        self.solar_elevation = self.solar_azimuth = None
        self.rising = self.phase = None
        self._next_change = None

        def update_location(_event):
            self.location = get_astral_location(self.hass)
            self.update_events(dt_util.utcnow())

        update_location(None)
        self.hass.bus.async_listen(EVENT_CORE_CONFIG_UPDATE, update_location)

    @property
    def name(self):
        """Return the name."""
        return "Sun"

    @property
    def state(self):
        """Return the state of the sun."""
        # 0.8333 is the same value as astral uses
        if self.solar_elevation > -0.833:
            return STATE_ABOVE_HORIZON

        return STATE_BELOW_HORIZON

    @property
    def state_attributes(self):
        """Return the state attributes of the sun."""
        return {
            STATE_ATTR_NEXT_DAWN: self.next_dawn.isoformat(),
            STATE_ATTR_NEXT_DUSK: self.next_dusk.isoformat(),
            STATE_ATTR_NEXT_MIDNIGHT: self.next_midnight.isoformat(),
            STATE_ATTR_NEXT_NOON: self.next_noon.isoformat(),
            STATE_ATTR_NEXT_RISING: self.next_rising.isoformat(),
            STATE_ATTR_NEXT_SETTING: self.next_setting.isoformat(),
            STATE_ATTR_ELEVATION: self.solar_elevation,
            STATE_ATTR_AZIMUTH: self.solar_azimuth,
            STATE_ATTR_RISING: self.rising,
        }

    def _check_event(self, utc_point_in_time, sun_event, before):
        next_utc = get_location_astral_event_next(
            self.location, sun_event, utc_point_in_time
        )
        if next_utc < self._next_change:
            self._next_change = next_utc
            self.phase = before
        return next_utc

    @callback
    def update_events(self, utc_point_in_time):
        """Update the attributes containing solar events."""
        self._next_change = utc_point_in_time + timedelta(days=400)

        # Work our way around the solar cycle, figure out the next
        # phase. Some of these are stored.
        self.location.solar_depression = "astronomical"
        self._check_event(utc_point_in_time, "dawn", PHASE_NIGHT)
        self.location.solar_depression = "nautical"
        self._check_event(utc_point_in_time, "dawn", PHASE_ASTRONOMICAL_TWILIGHT)
        self.location.solar_depression = "civil"
        self.next_dawn = self._check_event(
            utc_point_in_time, "dawn", PHASE_NAUTICAL_TWILIGHT
        )
        self.next_rising = self._check_event(
            utc_point_in_time, SUN_EVENT_SUNRISE, PHASE_TWILIGHT
        )
        self.location.solar_depression = -10
        self._check_event(utc_point_in_time, "dawn", PHASE_SMALL_DAY)
        self.next_noon = self._check_event(utc_point_in_time, "solar_noon", None)
        self._check_event(utc_point_in_time, "dusk", PHASE_DAY)
        self.next_setting = self._check_event(
            utc_point_in_time, SUN_EVENT_SUNSET, PHASE_SMALL_DAY
        )
        self.location.solar_depression = "civil"
        self.next_dusk = self._check_event(utc_point_in_time, "dusk", PHASE_TWILIGHT)
        self.location.solar_depression = "nautical"
        self._check_event(utc_point_in_time, "dusk", PHASE_NAUTICAL_TWILIGHT)
        self.location.solar_depression = "astronomical"
        self._check_event(utc_point_in_time, "dusk", PHASE_ASTRONOMICAL_TWILIGHT)
        self.next_midnight = self._check_event(
            utc_point_in_time, "solar_midnight", None
        )
        self.location.solar_depression = "civil"

        # if the event was solar midday or midnight, phase will now
        # be None. Solar noon doesn't always happen when the sun is
        # even in the day at the poles, so we can't rely on it.
        # Need to calculate phase if next is noon or midnight
        if self.phase is None:
            elevation = self.location.solar_elevation(self._next_change)
            if elevation >= 10:
                self.phase = PHASE_DAY
            elif elevation >= 0:
                self.phase = PHASE_SMALL_DAY
            elif elevation >= -6:
                self.phase = PHASE_TWILIGHT
            elif elevation >= -12:
                self.phase = PHASE_NAUTICAL_TWILIGHT
            elif elevation >= -18:
                self.phase = PHASE_ASTRONOMICAL_TWILIGHT
            else:
                self.phase = PHASE_NIGHT

        self.rising = self.next_noon < self.next_midnight

        _LOGGER.debug(
            "sun phase_update@%s: phase=%s", utc_point_in_time.isoformat(), self.phase
        )
        self.update_sun_position(utc_point_in_time)

        # Set timer for the next solar event
        event.async_track_point_in_utc_time(
            self.hass, self.update_events, self._next_change
        )
        _LOGGER.debug("next time: %s", self._next_change.isoformat())

    @callback
    def update_sun_position(self, utc_point_in_time):
        """Calculate the position of the sun."""
        self.solar_azimuth = round(self.location.solar_azimuth(utc_point_in_time), 2)
        self.solar_elevation = round(
            self.location.solar_elevation(utc_point_in_time), 2
        )

        _LOGGER.debug(
            "sun position_update@%s: elevation=%s azimuth=%s",
            utc_point_in_time.isoformat(),
            self.solar_elevation,
            self.solar_azimuth,
        )
        self.async_write_ha_state()

        # Next update as per the current phase
        delta = _PHASE_UPDATES[self.phase]
        # if the next update is within 1.25 of the next
        # position update just drop it
        if utc_point_in_time + delta * 1.25 > self._next_change:
            return
        event.async_track_point_in_utc_time(
            self.hass, self.update_sun_position, utc_point_in_time + delta
        )
