import secrets

from fastapi import HTTPException, Request, status


CSRF_COOKIE_NAME = "csrf_token"
CSRF_FORM_FIELD = "csrf_token"


def ensure_csrf_cookie(request: Request) -> str:
    token = request.cookies.get(CSRF_COOKIE_NAME)
    if token:
        return token
    return secrets.token_urlsafe(32)


def validate_csrf(request: Request, form_token: str) -> None:
    cookie_token = request.cookies.get(CSRF_COOKIE_NAME)
    if not cookie_token or not form_token or not secrets.compare_digest(cookie_token, form_token):
        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="CSRF-Validierung fehlgeschlagen.")