def parse_cache_control_directives(headers: Headers):
known_directives = {
# https://tools.ietf.org/html/rfc7234#section-5.2
"max-age": (int, True),
"max-stale": (int, False),
"min-fresh": (int, True),
"no-cache": (None, False),
"no-store": (None, False),
"no-transform": (None, False),
"only-if-cached": (None, False),
"must-revalidate": (None, False),
"public": (None, False),
"private": (None, False),
"proxy-revalidate": (None, False),
"s-maxage": (int, True),
}
cc_headers = headers.get("cache-control", "")
retval = {} # type: ignore
for cc_directive in cc_headers.split(","):
if not cc_directive.strip():
continue
parts = cc_directive.split("=", 1)
directive = parts[0].strip()
try:
typ, required = known_directives[directive]
except KeyError:
logger.debug("Ignoring unknown cache-control directive: %s",
directive)
continue
if not typ or not required:
retval[directive] = None
if typ:
try:
retval[directive] = typ(parts[1].strip())
except IndexError:
if required:
logger.debug(
"Missing value for cache-control "
"directive: %s",
directive,
)
except ValueError:
logger.debug(
"Invalid value for cache-control directive "
"%s, must be %s",
directive,
typ.__name__,
)
return retval
def check_vary_headers(request_headers: Headers,
cached_vary_data: dict) -> bool:
"""Verify our vary headers match."""
# Ensure that the Vary headers for the cached response match our
# request
# TODO: this should not be here, no reason for request headers to be so deep in deserialization.
for header, value in cached_vary_data.items():
if request_headers.get(header, None) != value:
return False
return True
async def process_headers(headers: Headers) -> Dict:
"""Filter out unwanted headers and return as a dictionary."""
headers = dict(headers)
header_keys = (
"user-agent",
"referer",
"accept-encoding",
"accept-language",
"x-real-ip",
"x-forwarded-for",
)
return {k: headers.get(k) for k in header_keys}
def get_vary_headers(request_headers: Headers, response: Response):
"""Get vary headers values for persisting in the cache for later checking"""
vary = {}
# Construct our vary headers
if "vary" in response.headers:
varied_headers = response.headers["vary"].split(",")
for header in varied_headers:
header = header.strip()
header_value = request_headers.get(header, None)
vary[header] = header_value
return vary
