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

from app.utils.redis_client import get_redis_client


def _safe_ip(request: Request) -> str:
    if not request.client or not request.client.host:
        return "unknown"
    return request.client.host


async def enforce_ip_rate_limit(
    request: Request,
    *,
    scope: str,
    limit: int,
    window_seconds: int = 60,
) -> None:
    if limit <= 0:
        return
    key = f"rl:{scope}:ip:{_safe_ip(request)}"
    await _enforce(key=key, limit=limit, window_seconds=window_seconds)


async def enforce_user_rate_limit(
    user_id: int,
    *,
    scope: str,
    limit: int,
    window_seconds: int = 60,
) -> None:
    if limit <= 0:
        return
    key = f"rl:{scope}:user:{user_id}"
    await _enforce(key=key, limit=limit, window_seconds=window_seconds)


async def _enforce(*, key: str, limit: int, window_seconds: int) -> None:
    try:
        redis = get_redis_client()
        current = await redis.incr(key)
        if current == 1:
            await redis.expire(key, window_seconds)
        if current > limit:
            ttl = await redis.ttl(key)
            retry_after = max(1, ttl if ttl and ttl > 0 else window_seconds)
            raise HTTPException(
                status_code=status.HTTP_429_TOO_MANY_REQUESTS,
                detail=f"Rate limit exceeded. Retry in {retry_after} seconds.",
            )
    except RedisError:
        # Fail-open in case of Redis outage to keep core API available.
        return