"""Async wrapper around the singleton PolicyEngine.

F-15 remediation: the global ``POLICY`` reference is now guarded by a
lock so concurrent FastAPI handlers can't race on init.
"""

from __future__ import annotations

import logging
import threading
from typing import Any, Optional

from backend.events.emitter import emit_policy

log = logging.getLogger(__name__)

_POLICY: Optional[Any] = None
_policy_lock = threading.Lock()


def init(policy_engine: Any) -> None:
    """Register the singleton policy engine."""
    global _POLICY
    with _policy_lock:
        _POLICY = policy_engine


def _get() -> Any:
    """Return the singleton, raising a clear error if init() was never called."""
    with _policy_lock:
        if _POLICY is None:
            raise RuntimeError("policy engine not initialised — call policy.api.init() first")
        return _POLICY


async def set_override(data: dict) -> dict:
    """Set ``data['key'] = data['value']`` on the singleton policy engine."""
    eng = _get()
    eng.set_override(data["key"], data["value"])
    await emit_policy(data["key"], data["value"])
    return {"status": "ok"}


async def clear_override(data: dict) -> dict:
    """Clear ``data['key']`` from the singleton policy engine."""
    eng = _get()
    eng.clear_override(data["key"])
    await emit_policy(data["key"], None)
    return {"status": "cleared"}