import time
from collections import defaultdict
from typing import Dict, Tuple

from fastapi import HTTPException, Request


class InMemoryRateLimiter:
    """基于滑动窗口的内存限流器。

    按 IP 地址追踪请求次数，超出阈值时抛出 429。
    适用于单实例部署；集群部署应替换为 Redis 后端。
    """

    def __init__(self, max_requests: int = 5, window_seconds: int = 60):
        self._max_requests = max_requests
        self._window_seconds = window_seconds
        self._requests: Dict[str, list[float]] = defaultdict(list)

    def _get_client_ip(self, request: Request) -> str:
        forwarded = request.headers.get("X-Forwarded-For")
        if forwarded:
            return forwarded.split(",")[0].strip()
        return request.client.host if request.client else "unknown"

    def _cleanup(self, key: str, now: float) -> None:
        cutoff = now - self._window_seconds
        self._requests[key] = [
            t for t in self._requests[key] if t > cutoff
        ]

    def check(self, request: Request) -> None:
        now = time.time()
        key = self._get_client_ip(request)
        self._cleanup(key, now)
        if len(self._requests[key]) >= self._max_requests:
            raise HTTPException(
                status_code=429,
                detail="请求过于频繁，请稍后再试",
            )
        self._requests[key].append(now)


register_limiter = InMemoryRateLimiter(max_requests=5, window_seconds=60)
login_limiter = InMemoryRateLimiter(max_requests=10, window_seconds=60)