"""Helpers for managing a pairing with a HomeKit accessory or bridge."""
import asyncio
import datetime
import logging

from homekit.exceptions import (
    AccessoryDisconnectedError,
    AccessoryNotFoundError,
    EncryptionError,
)
from homekit.model.services import ServicesTypes
from homekit.model.characteristics import CharacteristicsTypes

from homeassistant.helpers.event import async_track_time_interval

from .const import DOMAIN, HOMEKIT_ACCESSORY_DISPATCH, ENTITY_MAP


DEFAULT_SCAN_INTERVAL = datetime.timedelta(seconds=60)
RETRY_INTERVAL = 60  # seconds

_LOGGER = logging.getLogger(__name__)


def get_accessory_information(accessory):
    """Obtain the accessory information service of a HomeKit device."""
    result = {}
    for service in accessory["services"]:
        stype = service["type"].upper()
        if ServicesTypes.get_short(stype) != "accessory-information":
            continue
        for characteristic in service["characteristics"]:
            ctype = CharacteristicsTypes.get_short(characteristic["type"])
            if "value" in characteristic:
                result[ctype] = characteristic["value"]
    return result


def get_bridge_information(accessories):
    """Return the accessory info for the bridge."""
    for accessory in accessories:
        if accessory["aid"] == 1:
            return get_accessory_information(accessory)
    return get_accessory_information(accessories[0])


def get_accessory_name(accessory_info):
    """Return the name field of an accessory."""
    for field in ("name", "model", "manufacturer"):
        if field in accessory_info:
            return accessory_info[field]
    return None


class HKDevice:
    """HomeKit device."""

    def __init__(self, hass, config_entry, pairing_data):
        """Initialise a generic HomeKit device."""
        from homekit.controller.ip_implementation import IpPairing

        self.hass = hass
        self.config_entry = config_entry

        # We copy pairing_data because homekit_python may mutate it, but we
        # don't want to mutate a dict owned by a config entry.
        self.pairing_data = pairing_data.copy()

        self.pairing = IpPairing(self.pairing_data)

        self.accessories = {}
        self.config_num = 0

        # A list of callbacks that turn HK service metadata into entities
        self.listeners = []

        # The platorms we have forwarded the config entry so far. If a new
        # accessory is added to a bridge we may have to load additional
        # platforms. We don't want to load all platforms up front if its just
        # a lightbulb. And we dont want to forward a config entry twice
        # (triggers a Config entry already set up error)
        self.platforms = set()

        # This just tracks aid/iid pairs so we know if a HK service has been
        # mapped to a HA entity.
        self.entities = []

        # There are multiple entities sharing a single connection - only
        # allow one entity to use pairing at once.
        self.pairing_lock = asyncio.Lock()

        self.available = True

        self.signal_state_updated = "_".join((DOMAIN, self.unique_id, "state_updated"))

        # Current values of all characteristics homekit_controller is tracking.
        # Key is a (accessory_id, characteristic_id) tuple.
        self.current_state = {}

        self.pollable_characteristics = []

        # If this is set polling is active and can be disabled by calling
        # this method.
        self._polling_interval_remover = None

        # Never allow concurrent polling of the same accessory or bridge
        self._polling_lock = asyncio.Lock()
        self._polling_lock_warned = False

    def add_pollable_characteristics(self, characteristics):
        """Add (aid, iid) pairs that we need to poll."""
        self.pollable_characteristics.extend(characteristics)

    def remove_pollable_characteristics(self, accessory_id):
        """Remove all pollable characteristics by accessory id."""
        self.pollable_characteristics = [
            char for char in self.pollable_characteristics if char[0] != accessory_id
        ]

    def async_set_unavailable(self):
        """Mark state of all entities on this connection as unavailable."""
        self.available = False
        self.hass.helpers.dispatcher.async_dispatcher_send(self.signal_state_updated)

    async def async_setup(self):
        """Prepare to use a paired HomeKit device in homeassistant."""
        cache = self.hass.data[ENTITY_MAP].get_map(self.unique_id)
        if not cache:
            if await self.async_refresh_entity_map(self.config_num):
                self._polling_interval_remover = async_track_time_interval(
                    self.hass, self.async_update, DEFAULT_SCAN_INTERVAL
                )
                return True
            return False

        self.accessories = cache["accessories"]
        self.config_num = cache["config_num"]

        # Ensure the Pairing object has access to the latest version of the
        # entity map.
        self.pairing.pairing_data["accessories"] = self.accessories

        self.async_load_platforms()

        self.add_entities()

        await self.async_update()

        self._polling_interval_remover = async_track_time_interval(
            self.hass, self.async_update, DEFAULT_SCAN_INTERVAL
        )

        return True

    async def async_unload(self):
        """Stop interacting with device and prepare for removal from hass."""
        if self._polling_interval_remover:
            self._polling_interval_remover()

        unloads = []
        for platform in self.platforms:
            unloads.append(
                self.hass.config_entries.async_forward_entry_unload(
                    self.config_entry, platform
                )
            )

        results = await asyncio.gather(*unloads)

        return False not in results

    async def async_refresh_entity_map(self, config_num):
        """Handle setup of a HomeKit accessory."""
        try:
            async with self.pairing_lock:
                self.accessories = await self.hass.async_add_executor_job(
                    self.pairing.list_accessories_and_characteristics
                )
        except AccessoryDisconnectedError:
            # If we fail to refresh this data then we will naturally retry
            # later when Bonjour spots c# is still not up to date.
            return

        self.hass.data[ENTITY_MAP].async_create_or_update_map(
            self.unique_id, config_num, self.accessories
        )

        self.config_num = config_num

        # For BLE, the Pairing instance relies on the entity map to map
        # aid/iid to GATT characteristics. So push it to there as well.
        self.pairing.pairing_data["accessories"] = self.accessories

        self.async_load_platforms()

        # Register and add new entities that are available
        self.add_entities()

        await self.async_update()

        return True

    def add_listener(self, add_entities_cb):
        """Add a callback to run when discovering new entities."""
        self.listeners.append(add_entities_cb)
        self._add_new_entities([add_entities_cb])

    def add_entities(self):
        """Process the entity map and create HA entities."""
        self._add_new_entities(self.listeners)

    def _add_new_entities(self, callbacks):
        for accessory in self.accessories:
            aid = accessory["aid"]
            for service in accessory["services"]:
                iid = service["iid"]
                stype = ServicesTypes.get_short(service["type"].upper())
                service["stype"] = stype

                if (aid, iid) in self.entities:
                    # Don't add the same entity again
                    continue

                for listener in callbacks:
                    if listener(aid, service):
                        self.entities.append((aid, iid))
                        break

    def async_load_platforms(self):
        """Load any platforms needed by this HomeKit device."""
        for accessory in self.accessories:
            for service in accessory["services"]:
                stype = ServicesTypes.get_short(service["type"].upper())
                if stype not in HOMEKIT_ACCESSORY_DISPATCH:
                    continue

                platform = HOMEKIT_ACCESSORY_DISPATCH[stype]
                if platform in self.platforms:
                    continue

                self.hass.async_create_task(
                    self.hass.config_entries.async_forward_entry_setup(
                        self.config_entry, platform
                    )
                )
                self.platforms.add(platform)

    async def async_update(self, now=None):
        """Poll state of all entities attached to this bridge/accessory."""
        if not self.pollable_characteristics:
            _LOGGER.debug("HomeKit connection not polling any characteristics.")
            return

        if self._polling_lock.locked():
            if not self._polling_lock_warned:
                _LOGGER.warning(
                    "HomeKit controller update skipped as previous poll still in flight"
                )
                self._polling_lock_warned = True
            return

        if self._polling_lock_warned:
            _LOGGER.info(
                "HomeKit controller no longer detecting back pressure - not skipping poll"
            )
            self._polling_lock_warned = False

        async with self._polling_lock:
            _LOGGER.debug("Starting HomeKit controller update")

            try:
                new_values_dict = await self.get_characteristics(
                    self.pollable_characteristics
                )
            except AccessoryNotFoundError:
                # Not only did the connection fail, but also the accessory is not
                # visible on the network.
                self.async_set_unavailable()
                return
            except (AccessoryDisconnectedError, EncryptionError):
                # Temporary connection failure. Device is still available but our
                # connection was dropped.
                return

            self.process_new_events(new_values_dict)

            _LOGGER.debug("Finished HomeKit controller update")

    def process_new_events(self, new_values_dict):
        """Process events from accessory into HA state."""
        self.available = True

        for (aid, cid), value in new_values_dict.items():
            accessory = self.current_state.setdefault(aid, {})
            accessory[cid] = value

        self.hass.helpers.dispatcher.async_dispatcher_send(self.signal_state_updated)

    async def get_characteristics(self, *args, **kwargs):
        """Read latest state from homekit accessory."""
        async with self.pairing_lock:
            chars = await self.hass.async_add_executor_job(
                self.pairing.get_characteristics, *args, **kwargs
            )
        return chars

    async def put_characteristics(self, characteristics):
        """Control a HomeKit device state from Home Assistant."""
        chars = []
        for row in characteristics:
            chars.append((row["aid"], row["iid"], row["value"]))

        async with self.pairing_lock:
            results = await self.hass.async_add_executor_job(
                self.pairing.put_characteristics, chars
            )

        # Feed characteristics back into HA and update the current state
        # results will only contain failures, so anythin in characteristics
        # but not in results was applied successfully - we can just have HA
        # reflect the change immediately.

        new_entity_state = {}
        for row in characteristics:
            key = (row["aid"], row["iid"])

            # If the key was returned by put_characteristics() then the
            # change didnt work
            if key in results:
                continue

            # Otherwise it was accepted and we can apply the change to
            # our state
            new_entity_state[key] = {"value": row["value"]}

        self.process_new_events(new_entity_state)

    @property
    def unique_id(self):
        """
        Return a unique id for this accessory or bridge.

        This id is random and will change if a device undergoes a hard reset.
        """
        return self.pairing_data["AccessoryPairingID"]

    @property
    def connection_info(self):
        """Return accessory information for the main accessory."""
        return get_bridge_information(self.accessories)

    @property
    def name(self):
        """Name of the bridge accessory."""
        return get_accessory_name(self.connection_info) or self.unique_id