from __future__ import annotations

import secrets

from flask import request, session


def csrf_token() -> str:
    token = session.get("_csrf_token")
    if not token:
        token = secrets.token_urlsafe(32)
        session["_csrf_token"] = token
    return token


def validate_csrf_token() -> bool:
    expected = session.get("_csrf_token", "")
    received = request.form.get("csrf_token") or request.headers.get("X-CSRFToken", "")
    return bool(expected and received and secrets.compare_digest(expected, received))


def new_captcha() -> str:
    alphabet = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789"
    return "".join(secrets.choice(alphabet) for _ in range(5))