import re

from abc import ABC

from starlette.authentication import (

AuthenticationError,

)

class TokenExtractor(ABC):

"""

A class to extract the authorization token from a user request.

"""

def extract_access_token(self, **kwargs) -> str:

"""

Extract the authorization token from a user request.

The actual implementation has to specify what arguments have to be defined in the kwywork args `kwargs`

Returns:

The extracted access token.

"""

raise NotImplementedError()

def _extract_bearer_token(self, auth_header: str) -> str:

"""

Extract the bearer token from the authorization header value.

Args:

auth_header: The full value of the authorization header.

Returns:

str: The token value, without the `Bearer` part.

Raises:

AuthenticationError if the authorization token does not match the `Bearer` scheme.

"""

pattern = r"(?i)Bearer .+"

if not bool(re.match(pattern, auth_header)):

raise AuthenticationError(f"Expected Bearer schema, found {auth_header}")

_, access_token = auth_header.split()

return access_token

class NoAuthTokenExtractor(TokenExtractor):

"""

A `TokenExtractor` always returning an empty token

"""

def extract_access_token(self, **kwargs) -> str:

return ""