import typing

import tldextract
from flask import request, current_app


def get_allowed_root_domain() -> typing.Optional[str]:
    """Returns allowed root domain to set cookie or None."""

    root_domain = tldextract.extract(request.host).registered_domain
    if root_domain and request.host in current_app.config.get("ALLOWED_HOSTS"):
        return root_domain

    return None


def get_root_domain(url: str) -> typing.Optional[str]:
    """Returns registered root domain for given url."""

    return tldextract.extract(url).registered_domain


def get_allowed_host() -> typing.Optional[str]:
    """Returns allowed host to set cookie or None."""

    if request.host in current_app.config.get("ALLOWED_HOSTS"):
        return request.host

    return None


def get_allowed_subdomain(url: str) -> typing.Optional[str]:
    """
    Returns allowed host with subdomain if it is located
    on the allowed domain.
    """

    extracted = tldextract.extract(url)
    subdomain = extracted.fqdn
    root_domain = extracted.registered_domain
    allowed_root_domains = [
        get_root_domain(d) for d in current_app.config.get("ALLOWED_HOSTS")
    ]
    if root_domain not in allowed_root_domains:
        return None

    return subdomain