from __future__ import annotations

import re
from typing import Mapping

from app.models import SubscriptionUserInfo

_SUBSCRIPTION_FIELDS = re.compile(r"(upload|download|total|expire)=(\d+)")


def get_header_case_insensitive(headers: Mapping[str, str], name: str) -> str | None:
    target = name.lower()
    for key, value in headers.items():
        if key.lower() == target:
            return value
    return None


def parse_subscription_userinfo(headers: Mapping[str, str]) -> SubscriptionUserInfo | None:
    raw = get_header_case_insensitive(headers, "Subscription-Userinfo")
    if not raw:
        return None

    values: dict[str, int] = {}
    for key, value in _SUBSCRIPTION_FIELDS.findall(raw):
        values[key] = int(value)

    info = SubscriptionUserInfo(**values)
    return None if info.is_empty() else info