"""User subscription expiration helpers."""

from __future__ import annotations

from datetime import datetime, timedelta
from typing import Optional


def user_is_expired(user: dict, *, now: Optional[datetime] = None) -> bool:
    """True when absolute expiration_date is in the past."""
    exp_str = user.get('expiration_date')
    if not exp_str:
        return False
    try:
        exp_date = datetime.fromisoformat(str(exp_str))
    except Exception:
        return False
    return (now or datetime.now()) > exp_date


def maybe_start_user_expiration(data: dict, user_id: str, *, now: Optional[datetime] = None) -> Optional[str]:
    """If user waits for first config use, start the countdown.

    Returns the new expiration_date ISO string when activated, else None.
    """
    if not user_id:
        return None
    user = next((u for u in data.get('users', []) if u.get('id') == user_id), None)
    if not user:
        return None
    if not user.get('expire_after_first_use'):
        return None
    if user.get('expiration_date'):
        return None
    days = int(user.get('expiration_days') or 0)
    if days <= 0:
        return None
    stamp = now or datetime.now()
    expires = stamp + timedelta(days=days)
    iso = expires.isoformat()
    user['expiration_date'] = iso
    return iso