mirror of https://github.com/home-assistant/core
146 lines
5.0 KiB
Python
146 lines
5.0 KiB
Python
"""Manage allocation of accessory ID's.
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HomeKit needs to allocate unique numbers to each accessory. These need to
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be stable between reboots and upgrades.
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Using a hash function to generate them means collisions. It also means you
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can't change the hash without causing breakages for HA users.
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This module generates and stores them in a HA storage.
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"""
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from __future__ import annotations
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from collections.abc import Generator
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import random
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from fnvhash import fnv1a_32
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from homeassistant.core import HomeAssistant, callback
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from homeassistant.helpers import entity_registry as er
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from homeassistant.helpers.storage import Store
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from .util import get_aid_storage_filename_for_entry_id
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AID_MANAGER_STORAGE_VERSION = 1
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AID_MANAGER_SAVE_DELAY = 2
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ALLOCATIONS_KEY = "allocations"
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UNIQUE_IDS_KEY = "unique_ids"
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INVALID_AIDS = (0, 1)
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AID_MIN = 2
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AID_MAX = 18446744073709551615
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def get_system_unique_id(entity: er.RegistryEntry) -> str:
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"""Determine the system wide unique_id for an entity."""
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return f"{entity.platform}.{entity.domain}.{entity.unique_id}"
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def _generate_aids(unique_id: str | None, entity_id: str) -> Generator[int, None, None]:
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"""Generate accessory aid."""
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if unique_id:
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# Use fnv1a_32 of the unique id as
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# fnv1a_32 has less collisions than
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# adler32
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yield fnv1a_32(unique_id.encode("utf-8"))
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# If there is no unique id we use
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# fnv1a_32 as it is unlikely to collide
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yield fnv1a_32(entity_id.encode("utf-8"))
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# If called again resort to random allocations.
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# Given the size of the range its unlikely we'll encounter duplicates
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# But try a few times regardless
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for _ in range(5):
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yield random.randrange(AID_MIN, AID_MAX)
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class AccessoryAidStorage:
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"""Holds a map of entity ID to HomeKit ID.
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Will generate new ID's, ensure they are unique and store them to make sure they
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persist over reboots.
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"""
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def __init__(self, hass: HomeAssistant, entry_id: str) -> None:
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"""Create a new entity map store."""
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self.hass = hass
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self.allocations: dict[str, int] = {}
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self.allocated_aids: set[int] = set()
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self._entry_id = entry_id
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self.store: Store | None = None
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self._entity_registry: er.EntityRegistry | None = None
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async def async_initialize(self) -> None:
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"""Load the latest AID data."""
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self._entity_registry = er.async_get(self.hass)
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aidstore = get_aid_storage_filename_for_entry_id(self._entry_id)
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self.store = Store(self.hass, AID_MANAGER_STORAGE_VERSION, aidstore)
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if not (raw_storage := await self.store.async_load()):
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# There is no data about aid allocations yet
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return
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assert isinstance(raw_storage, dict)
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self.allocations = raw_storage.get(ALLOCATIONS_KEY, {})
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self.allocated_aids = set(self.allocations.values())
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def get_or_allocate_aid_for_entity_id(self, entity_id: str) -> int:
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"""Generate a stable aid for an entity id."""
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assert self._entity_registry is not None
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if not (entity := self._entity_registry.async_get(entity_id)):
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return self.get_or_allocate_aid(None, entity_id)
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sys_unique_id = get_system_unique_id(entity)
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return self.get_or_allocate_aid(sys_unique_id, entity_id)
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def get_or_allocate_aid(self, unique_id: str | None, entity_id: str) -> int:
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"""Allocate (and return) a new aid for an accessory."""
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if unique_id and unique_id in self.allocations:
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return self.allocations[unique_id]
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if entity_id in self.allocations:
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return self.allocations[entity_id]
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for aid in _generate_aids(unique_id, entity_id):
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if aid in INVALID_AIDS:
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continue
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if aid not in self.allocated_aids:
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# Prefer the unique_id over the entitiy_id
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storage_key = unique_id or entity_id
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self.allocations[storage_key] = aid
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self.allocated_aids.add(aid)
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self.async_schedule_save()
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return aid
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raise ValueError(
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f"Unable to generate unique aid allocation for {entity_id} [{unique_id}]"
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)
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def delete_aid(self, storage_key: str) -> None:
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"""Delete an aid allocation."""
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if storage_key not in self.allocations:
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return
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aid = self.allocations.pop(storage_key)
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self.allocated_aids.discard(aid)
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self.async_schedule_save()
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@callback
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def async_schedule_save(self) -> None:
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"""Schedule saving the entity map cache."""
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assert self.store is not None
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self.store.async_delay_save(self._data_to_save, AID_MANAGER_SAVE_DELAY)
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async def async_save(self) -> None:
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"""Save the entity map cache."""
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assert self.store is not None
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return await self.store.async_save(self._data_to_save())
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@callback
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def _data_to_save(self) -> dict:
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"""Return data of entity map to store in a file."""
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return {ALLOCATIONS_KEY: self.allocations}
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