import logging

from fastapi import HTTPException, Request, status
from redis.exceptions import RedisError

logger = logging.getLogger(__name__)


class RateLimiter:
    """Sliding window rate limiter backed by Redis.

    Usage as FastAPI dependency:
        @router.post("/action", dependencies=[Depends(RateLimiter(times=5, seconds=60))])
    """

    def __init__(self, times: int = 10, seconds: int = 60):
        self.times = times
        self.seconds = seconds

    async def __call__(self, request: Request) -> None:
        redis = getattr(request.app.state, "redis", None)
        if redis is None:
            return

        identifier = self._get_identifier(request)
        key = f"rl:{request.url.path}:{identifier}"

        try:
            pipe = redis.pipeline()
            pipe.incr(key)
            pipe.expire(key, self.seconds)
            results = await pipe.execute()
            current = results[0]
        except RedisError:
            logger.warning("Rate limiter skipped because Redis is unavailable", exc_info=True)
            return

        if current > self.times:
            raise HTTPException(
                status_code=status.HTTP_429_TOO_MANY_REQUESTS,
                detail="Too many requests, please try again later",
            )

    @staticmethod
    def _get_identifier(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"