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"""Utility functions for parsing and converting expiration values"""
from datetime import datetime, timedelta, timezone
from email.utils import parsedate_to_datetime
from fnmatch import fnmatch
from logging import getLogger
from math import ceil
from typing import Optional
from .._utils import try_int
from . import ExpirationPatterns, ExpirationTime
# Special expiration values that may be set by either headers or keyword args
DO_NOT_CACHE = 0x0D0E0200020704 # Per RFC 4824
EXPIRE_IMMEDIATELY = 0
NEVER_EXPIRE = -1
logger = getLogger(__name__)
def get_expiration_datetime(
expire_after: ExpirationTime,
start_time: Optional[datetime] = None,
negative_delta: bool = False,
) -> Optional[datetime]:
"""Convert an expiration value in any supported format to an absolute datetime"""
# Never expire (or do not cache, in which case expiration won't be used)
if expire_after is None or expire_after in [NEVER_EXPIRE, DO_NOT_CACHE]:
return None
# Expire immediately
elif try_int(expire_after) == EXPIRE_IMMEDIATELY:
return start_time or datetime.utcnow()
# Already a datetime or datetime str
if isinstance(expire_after, str):
return _parse_http_date(expire_after)
elif isinstance(expire_after, datetime):
return _to_utc(expire_after)
# Otherwise, it must be a timedelta or time in seconds
if not isinstance(expire_after, timedelta):
expire_after = timedelta(seconds=expire_after)
if negative_delta:
expire_after = -expire_after
return (start_time or datetime.utcnow()) + expire_after
def get_expiration_seconds(expire_after: ExpirationTime) -> int:
"""Convert an expiration value in any supported format to an expiration time in seconds"""
if expire_after == DO_NOT_CACHE:
return DO_NOT_CACHE
expires = get_expiration_datetime(expire_after)
return ceil((expires - datetime.utcnow()).total_seconds()) if expires else NEVER_EXPIRE
def get_url_expiration(
url: Optional[str], urls_expire_after: Optional[ExpirationPatterns] = None
) -> ExpirationTime:
"""Check for a matching per-URL expiration, if any"""
if not url:
return None
for pattern, expire_after in (urls_expire_after or {}).items():
if _url_match(url, pattern):
logger.debug(f'URL {url} matched pattern "{pattern}": {expire_after}')
return expire_after
return None
def _parse_http_date(value: str) -> Optional[datetime]:
"""Attempt to parse an HTTP (RFC 5322-compatible) timestamp"""
try:
expire_after = parsedate_to_datetime(value)
return _to_utc(expire_after)
except (TypeError, ValueError):
logger.debug(f'Failed to parse timestamp: {value}')
return None
def _to_utc(dt: datetime):
"""All internal datetimes are UTC and timezone-naive. Convert any user/header-provided
datetimes to the same format.
"""
if dt.tzinfo:
dt = dt.astimezone(timezone.utc)
dt = dt.replace(tzinfo=None)
return dt
def _url_match(url: str, pattern: str) -> bool:
"""Determine if a URL matches a pattern
Args:
url: URL to test. Its base URL (without protocol) will be used.
pattern: Glob pattern to match against. A recursive wildcard will be added if not present
Example:
>>> url_match('https://httpbin.org/delay/1', 'httpbin.org/delay')
True
>>> url_match('https://httpbin.org/stream/1', 'httpbin.org/*/1')
True
>>> url_match('https://httpbin.org/stream/2', 'httpbin.org/*/1')
False
"""
url = url.split('://')[-1]
pattern = pattern.split('://')[-1].rstrip('*') + '**'
return fnmatch(url, pattern)
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