utils.py

"""Authentication utility functions."""

from fastapi import HTTPException
from starlette.datastructures import Headers

from models.responses import UnauthorizedResponse


def extract_user_token(headers: Headers) -> str:
    """Extract the bearer token from an HTTP Authorization header.

    Parameters:
        headers (Headers): Incoming request headers from which the
        Authorization header will be read.

    Returns:
        str: The bearer token string extracted from the header.

    Raises:
        HTTPException: If the Authorization header is missing or malformed.
    """
    authorization_header = headers.get("Authorization")
    if not authorization_header:
        response = UnauthorizedResponse(cause="No Authorization header found")
        raise HTTPException(**response.model_dump())

    scheme_and_token = authorization_header.strip().split()
    if len(scheme_and_token) != 2 or scheme_and_token[0].lower() != "bearer":
        response = UnauthorizedResponse(cause="No token found in Authorization header")
        raise HTTPException(**response.model_dump())

    return scheme_and_token[1]