Reduce complexity of DNSRecord (#915)

- Use constants for calculations in is_expired/is_stale/is_recent

tests/services/test_info.py

@@ -187,8 +187,7 @@ def test_service_info_rejects_expired_records(self):
             ttl,
             b'\x04ff=0\x04ci=3\x04sf=0\x0bsh=6fLM5A==',
         )
-        expired_record.created = 1000
-        expired_record._expiration_time = 1000
+        expired_record.set_created_ttl(1000, 1)
         info.update_record(zc, now, expired_record)
         assert info.properties[b"ci"] == b"2"
         zc.close()

zeroconf/_dns.py

@@ -31,9 +31,6 @@
     _CLASSES,
     _CLASS_MASK,
     _CLASS_UNIQUE,
-    _EXPIRE_FULL_TIME_PERCENT,
-    _EXPIRE_STALE_TIME_PERCENT,
-    _RECENT_TIME_PERCENT,
     _TYPES,
     _TYPE_ANY,
 )
@@ -45,6 +42,11 @@
 _BASE_MAX_SIZE = _LEN_SHORT + _LEN_SHORT + _LEN_INT + _LEN_SHORT  # type  # class  # ttl  # length
 _NAME_COMPRESSION_MIN_SIZE = _LEN_BYTE * 2
 
+_EXPIRE_FULL_TIME_MS = 1000
+_EXPIRE_STALE_TIME_MS = 500
+_RECENT_TIME_MS = 250
+
+
 if TYPE_CHECKING:
     # https://github.com/PyCQA/pylint/issues/3525
     from ._protocol import DNSIncoming, DNSOutgoing  # pylint: disable=cyclic-import
@@ -154,7 +156,7 @@ class DNSRecord(DNSEntry):
 
     """A DNS record - like a DNS entry, but has a TTL"""
 
-    __slots__ = ('ttl', 'created', '_expiration_time', '_stale_time', '_recent_time')
+    __slots__ = ('ttl', 'created')
 
     # TODO: Switch to just int ttl
     def __init__(
@@ -163,9 +165,6 @@ def __init__(
         super().__init__(name, type_, class_)
         self.ttl = ttl
         self.created = created or current_time_millis()
-        self._expiration_time: Optional[float] = None
-        self._stale_time: Optional[float] = None
-        self._recent_time: Optional[float] = None
 
     def __eq__(self, other: Any) -> bool:  # pylint: disable=no-self-use
         """Abstract method"""
@@ -189,27 +188,19 @@ def get_expiration_time(self, percent: int) -> float:
     # TODO: Switch to just int here
     def get_remaining_ttl(self, now: float) -> Union[int, float]:
         """Returns the remaining TTL in seconds."""
-        if self._expiration_time is None:
-            self._expiration_time = self.get_expiration_time(_EXPIRE_FULL_TIME_PERCENT)
-        return max(0, millis_to_seconds(self._expiration_time - now))
+        return max(0, millis_to_seconds((self.created + (_EXPIRE_FULL_TIME_MS * self.ttl)) - now))
 
     def is_expired(self, now: float) -> bool:
         """Returns true if this record has expired."""
-        if self._expiration_time is None:
-            self._expiration_time = self.get_expiration_time(_EXPIRE_FULL_TIME_PERCENT)
-        return self._expiration_time <= now
+        return self.created + (_EXPIRE_FULL_TIME_MS * self.ttl) <= now
 
     def is_stale(self, now: float) -> bool:
         """Returns true if this record is at least half way expired."""
-        if self._stale_time is None:
-            self._stale_time = self.get_expiration_time(_EXPIRE_STALE_TIME_PERCENT)
-        return self._stale_time <= now
+        return self.created + (_EXPIRE_STALE_TIME_MS * self.ttl) <= now
 
     def is_recent(self, now: float) -> bool:
         """Returns true if the record more than one quarter of its TTL remaining."""
-        if self._recent_time is None:
-            self._recent_time = self.get_expiration_time(_RECENT_TIME_PERCENT)
-        return self._recent_time > now
+        return self.created + (_RECENT_TIME_MS * self.ttl) > now
 
     def reset_ttl(self, other: 'DNSRecord') -> None:
         """Sets this record's TTL and created time to that of
@@ -220,9 +211,6 @@ def set_created_ttl(self, created: float, ttl: Union[float, int]) -> None:
         """Set the created and ttl of a record."""
         self.created = created
         self.ttl = ttl
-        self._expiration_time = None
-        self._stale_time = None
-        self._recent_time = None
 
     def write(self, out: 'DNSOutgoing') -> None:  # pylint: disable=no-self-use
         """Abstract method"""

zeroconf/const.py

@@ -145,10 +145,7 @@
 _HAS_ONLY_A_TO_Z_NUM_HYPHEN_UNDERSCORE = re.compile(r'^[A-Za-z0-9\-\_]+$')
 _HAS_ASCII_CONTROL_CHARS = re.compile(r'[\x00-\x1f\x7f]')
 
-_EXPIRE_FULL_TIME_PERCENT = 100
-_EXPIRE_STALE_TIME_PERCENT = 50
 _EXPIRE_REFRESH_TIME_PERCENT = 75
-_RECENT_TIME_PERCENT = 25
 
 _LOCAL_TRAILER = '.local.'
 _TCP_PROTOCOL_LOCAL_TRAILER = '._tcp.local.'