from __future__ import annotations
import dataclasses
import typing
import weakref
from typing import Callable, Iterator, List, Optional, Tuple, Union
from flask import request
from flask.wrappers import Response
from limits import RateLimitItem, parse_many
from limits.strategies import RateLimiter
if typing.TYPE_CHECKING:
from .extension import Limiter
[docs]
class RequestLimit:
"""
Provides details of a rate limit within the context of a request
"""
#: The instance of the rate limit
limit: RateLimitItem
#: The full key for the request against which the rate limit is tested
key: str
#: Whether the limit was breached within the context of this request
breached: bool
#: Whether the limit is a shared limit
shared: bool
def __init__(
self,
extension: Limiter,
limit: RateLimitItem,
request_args: List[str],
breached: bool,
shared: bool,
) -> None:
self.extension: weakref.ProxyType[Limiter] = weakref.proxy(extension)
self.limit = limit
self.request_args = request_args
self.key = limit.key_for(*request_args)
self.breached = breached
self.shared = shared
self._window: Optional[Tuple[int, int]] = None
@property
def limiter(self) -> RateLimiter:
return typing.cast(RateLimiter, self.extension.limiter)
@property
def window(self) -> Tuple[int, int]:
if not self._window:
self._window = self.limiter.get_window_stats(self.limit, *self.request_args)
return self._window
@property
def reset_at(self) -> int:
"""Timestamp at which the rate limit will be reset"""
return int(self.window[0] + 1)
@property
def remaining(self) -> int:
"""Quantity remaining for this rate limit"""
return self.window[1]
@dataclasses.dataclass(eq=True, unsafe_hash=True)
class Limit:
"""
simple wrapper to encapsulate limits and their context
"""
limit: RateLimitItem
key_func: Callable[[], str]
_scope: Optional[Union[str, Callable[[str], str]]]
per_method: bool = False
methods: Optional[Tuple[str, ...]] = None
error_message: Optional[str] = None
exempt_when: Optional[Callable[[], bool]] = None
override_defaults: Optional[bool] = False
deduct_when: Optional[Callable[[Response], bool]] = None
on_breach: Optional[Callable[[RequestLimit], Optional[Response]]] = None
_cost: Union[Callable[[], int], int] = 1
shared: bool = False
def __post_init__(self) -> None:
if self.methods:
self.methods = tuple([k.lower() for k in self.methods])
@property
def is_exempt(self) -> bool:
"""Check if the limit is exempt."""
if self.exempt_when:
return self.exempt_when()
return False
@property
def scope(self) -> Optional[str]:
return (
self._scope(request.endpoint or "")
if callable(self._scope)
else self._scope
)
@property
def cost(self) -> int:
if isinstance(self._cost, int):
return self._cost
return self._cost()
@property
def method_exempt(self) -> bool:
"""Check if the limit is not applicable for this method"""
return self.methods is not None and request.method.lower() not in self.methods
def scope_for(self, endpoint: str, method: Optional[str]) -> str:
"""
Derive final bucket (scope) for this limit given the endpoint
and request method. If the limit is shared between multiple
routes, the scope does not include the endpoint.
"""
limit_scope = self.scope
if limit_scope:
if self.shared:
scope = limit_scope
else:
scope = f"{endpoint}:{limit_scope}"
else:
scope = endpoint
if self.per_method:
assert method
scope += f":{method.upper()}"
return scope
@dataclasses.dataclass(eq=True, unsafe_hash=True)
class LimitGroup:
"""
represents a group of related limits either from a string or a callable
that returns one
"""
limit_provider: Union[Callable[[], str], str]
key_function: Callable[[], str]
scope: Optional[Union[str, Callable[[str], str]]] = None
methods: Optional[Tuple[str, ...]] = None
error_message: Optional[str] = None
exempt_when: Optional[Callable[[], bool]] = None
override_defaults: Optional[bool] = False
deduct_when: Optional[Callable[[Response], bool]] = None
on_breach: Optional[Callable[[RequestLimit], Optional[Response]]] = None
per_method: bool = False
cost: Optional[Union[Callable[[], int], int]] = None
shared: bool = False
def __iter__(self) -> Iterator[Limit]:
limit_str = (
self.limit_provider()
if callable(self.limit_provider)
else self.limit_provider
)
limit_items = parse_many(limit_str) if limit_str else []
for limit in limit_items:
yield Limit(
limit,
self.key_function,
self.scope,
self.per_method,
self.methods,
self.error_message,
self.exempt_when,
self.override_defaults,
self.deduct_when,
self.on_breach,
self.cost or 1,
self.shared,
)