import json
from datetime import datetime, timezone

class AccessControl:
    _ACCESS_FILE = "./data/access.json"

    def __init__(self):
        self._access = self._load_access()

    def _load_access(self) -> dict:
        try:
            with open(self._ACCESS_FILE, "r") as f:
                return json.load(f)
        except FileNotFoundError:
            return {}

    def _save_access(self):
        with open(self._ACCESS_FILE, "w") as f:
            json.dump(self._access, f)

    def get_grantor(self, user_id: str, gate: str) -> str:
        access = self._access.get(user_id, {})
        entry = access.get(gate) or access.get("all")
        return entry.get("grantor", "") if entry else ""

    def can_open_gate(self, user_id: str, gate: str) -> bool:
        access = self._access.get(user_id, {})
        entry = access.get(gate) or access.get("all")
        if not entry or entry.get("type") != "timed":
            return False
        if datetime.now(timezone.utc) < datetime.fromisoformat(entry["expires_at"].replace("Z", "+00:00")):
            return True
        return False

    def grant_access(self, user_id: str, gate: str, expires_at: str, grantor_id: str):
        user_access = self._access.get(user_id, {})
        user_access[gate] = {
            "type": "timed",
            "granted_at": datetime.now(timezone.utc).isoformat(),
            "expires_at": expires_at,
            "grantor": grantor_id,
            "last_used_at": None
        }
        self._access[user_id] = user_access
        self._save_access()