"""
Lightweight in-process rate limiting helpers.
"""

from __future__ import annotations

import threading
import time
from collections import defaultdict, deque

from fastapi import HTTPException, Request, status

_lock = threading.Lock()
_hits: dict[str, deque[float]] = defaultdict(deque)


def _client_ip(request: Request) -> str:
    if request.client and request.client.host:
        return request.client.host
    return "unknown"


def enforce_rate_limit(
    request: Request,
    *,
    scope: str,
    max_requests: int,
    window_seconds: int,
) -> None:
    now = time.time()
    ip = _client_ip(request)
    key = f"{scope}:{ip}"
    cutoff = now - window_seconds

    with _lock:
        dq = _hits[key]
        while dq and dq[0] <= cutoff:
            dq.popleft()
        if len(dq) >= max_requests:
            raise HTTPException(
                status_code=status.HTTP_429_TOO_MANY_REQUESTS,
                detail=f"Too many requests for {scope}. Please try again later.",
            )
        dq.append(now)