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"""Add support for discovering mDNS services."""
import logging
from typing import List # noqa: F401
from zeroconf import DNSPointer, DNSRecord
from zeroconf import Error as ZeroconfError
from zeroconf import ServiceBrowser, ServiceInfo, ServiceStateChange, Zeroconf
_LOGGER = logging.getLogger(__name__)
class FastServiceBrowser(ServiceBrowser):
"""ServiceBrowser that does not process record updates."""
def update_record(self, zc: Zeroconf, now: float, record: DNSRecord) -> None:
"""Ignore record updates for non-ptrs."""
if record.name not in self.types or not isinstance(record, DNSPointer):
return
super().update_record(zc, now, record)
class MDNS:
"""Base class to discover mDNS services."""
def __init__(self, zeroconf_instance=None):
"""Initialize the discovery."""
self.zeroconf = zeroconf_instance
self._created_zeroconf = False
self.services = [] # type: List[ServiceInfo]
self._browser = None # type: ServiceBrowser
def register_service(self, service):
"""Register a mDNS service."""
self.services.append(service)
def start(self):
"""Start discovery."""
try:
if not self.zeroconf:
self.zeroconf = Zeroconf()
self._created_zeroconf = True
services_by_type = {}
for service in self.services:
services_by_type.setdefault(service.typ, [])
services_by_type[service.typ].append(service)
def _service_update(zeroconf, service_type, name, state_change):
if state_change == ServiceStateChange.Added:
for service in services_by_type[service_type]:
try:
service.add_service(zeroconf, service_type, name)
except ZeroconfError:
_LOGGER.exception("Failed to add service %s", name)
elif state_change == ServiceStateChange.Removed:
for service in services_by_type[service_type]:
service.remove_service(zeroconf, service_type, name)
types = [service.typ for service in self.services]
self._browser = FastServiceBrowser(
self.zeroconf, types, handlers=[_service_update]
)
except Exception: # pylint: disable=broad-except
self.stop()
raise
def stop(self):
"""Stop discovering."""
if self._browser:
self._browser.cancel()
self._browser = None
for service in self.services:
service.reset()
if self._created_zeroconf:
self.zeroconf.close()
self.zeroconf = None
@property
def entries(self):
"""Return all entries in the cache."""
return self.zeroconf.cache.entries()
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