import threading
import time
from collections import defaultdict

from fastapi import Request

from app.core.errors import AppError

_buckets: dict[str, list[float]] = defaultdict(list)
_lock = threading.Lock()


def _client_ip(request: Request) -> str:
    forwarded = request.headers.get("x-forwarded-for")
    if forwarded:
        return forwarded.split(",")[0].strip()
    if request.client and request.client.host:
        return request.client.host
    return "unknown"


def enforce_rate_limit(request: Request, *, scope: str, limit: int, window_seconds: int) -> None:
    """In-memory sliding window limiter (per process). Use edge/WAF limits in production at scale."""
    import os

    if os.environ.get("DESI_CLANS_DISABLE_RATE_LIMIT", "").lower() in {"1", "true", "yes"}:
        return
    if limit <= 0:
        return
    key = f"{scope}:{_client_ip(request)}"
    now = time.time()
    with _lock:
        window = _buckets[key]
        window[:] = [stamp for stamp in window if now - stamp < window_seconds]
        if len(window) >= limit:
            raise AppError("Too many requests. Try again shortly.", status_code=429)
        window.append(now)