"""Provide a way to connect devices to one physical location."""
import logging
import uuid
from asyncio import Event
from collections import OrderedDict
from typing import MutableMapping  # noqa: F401
from typing import Iterable, Optional, cast

import attr

from homeassistant.core import callback
from homeassistant.loader import bind_hass

from .typing import HomeAssistantType

_LOGGER = logging.getLogger(__name__)

DATA_REGISTRY = 'area_registry'
EVENT_AREA_REGISTRY_UPDATED = 'area_registry_updated'
STORAGE_KEY = 'core.area_registry'
STORAGE_VERSION = 1
SAVE_DELAY = 10


@attr.s(slots=True, frozen=True)
class AreaEntry:
    """Area Registry Entry."""

    name = attr.ib(type=str, default=None)
    id = attr.ib(type=str, default=attr.Factory(lambda: uuid.uuid4().hex))


class AreaRegistry:
    """Class to hold a registry of areas."""

    def __init__(self, hass: HomeAssistantType) -> None:
        """Initialize the area registry."""
        self.hass = hass
        self.areas = {}  # type: MutableMapping[str, AreaEntry]
        self._store = hass.helpers.storage.Store(STORAGE_VERSION, STORAGE_KEY)

    @callback
    def async_get_area(self, area_id: str) -> Optional[AreaEntry]:
        """Get all areas."""
        return self.areas.get(area_id)

    @callback
    def async_list_areas(self) -> Iterable[AreaEntry]:
        """Get all areas."""
        return self.areas.values()

    @callback
    def async_create(self, name: str) -> AreaEntry:
        """Create a new area."""
        if self._async_is_registered(name):
            raise ValueError('Name is already in use')

        area = AreaEntry()
        self.areas[area.id] = area

        created = self._async_update(area.id, name=name)

        self.hass.bus.async_fire(EVENT_AREA_REGISTRY_UPDATED, {
            'action': 'create',
            'area_id': created.id,
        })

        return created

    async def async_delete(self, area_id: str) -> None:
        """Delete area."""
        device_registry = await \
            self.hass.helpers.device_registry.async_get_registry()
        device_registry.async_clear_area_id(area_id)

        del self.areas[area_id]

        self.hass.bus.async_fire(EVENT_AREA_REGISTRY_UPDATED, {
            'action': 'remove',
            'area_id': area_id,
        })

        self.async_schedule_save()

    @callback
    def async_update(self, area_id: str, name: str) -> AreaEntry:
        """Update name of area."""
        updated = self._async_update(area_id, name)
        self.hass.bus.async_fire(EVENT_AREA_REGISTRY_UPDATED, {
            'action': 'update',
            'area_id': area_id,
        })
        return updated

    @callback
    def _async_update(self, area_id: str, name: str) -> AreaEntry:
        """Update name of area."""
        old = self.areas[area_id]

        changes = {}

        if name == old.name:
            return old

        if self._async_is_registered(name):
            raise ValueError('Name is already in use')

        changes['name'] = name

        new = self.areas[area_id] = attr.evolve(old, **changes)
        self.async_schedule_save()
        return new

    @callback
    def _async_is_registered(self, name: str) -> Optional[AreaEntry]:
        """Check if a name is currently registered."""
        for area in self.areas.values():
            if name == area.name:
                return area
        return None

    async def async_load(self) -> None:
        """Load the area registry."""
        data = await self._store.async_load()

        areas = OrderedDict()  # type: OrderedDict[str, AreaEntry]

        if data is not None:
            for area in data['areas']:
                areas[area['id']] = AreaEntry(
                    name=area['name'],
                    id=area['id']
                )

        self.areas = areas

    @callback
    def async_schedule_save(self) -> None:
        """Schedule saving the area registry."""
        self._store.async_delay_save(self._data_to_save, SAVE_DELAY)

    @callback
    def _data_to_save(self) -> dict:
        """Return data of area registry to store in a file."""
        data = {}

        data['areas'] = [
            {
                'name': entry.name,
                'id': entry.id,
            } for entry in self.areas.values()
        ]

        return data


@bind_hass
async def async_get_registry(hass: HomeAssistantType) -> AreaRegistry:
    """Return area registry instance."""
    reg_or_evt = hass.data.get(DATA_REGISTRY)

    if not reg_or_evt:
        evt = hass.data[DATA_REGISTRY] = Event()

        reg = AreaRegistry(hass)
        await reg.async_load()

        hass.data[DATA_REGISTRY] = reg
        evt.set()
        return reg

    if isinstance(reg_or_evt, Event):
        evt = reg_or_evt
        await evt.wait()
        return cast(AreaRegistry, hass.data.get(DATA_REGISTRY))

    return cast(AreaRegistry, reg_or_evt)