# -*- coding: utf-8 -*-
"""公网限流（FastAPI 栈）——按 IP 滑动窗口，与 Flask 侧 _rate_ok 同一实现口径。

复用 core.state.RATE_BUCKETS/_RATE_LOCK，使两栈在迁移期共享同一批限流桶
（同一 IP 无论打到哪个栈都计入同一窗口），避免出现「绕到另一个框架即绕过限流」。
"""
import collections
import time

from fastapi import Request

from core.config import RESULT_RETENTION_SECONDS  # noqa: F401 - 保持与 Flask 侧常量同源
from core.state import RATE_BUCKETS, RATE_LOCK
from web.errors import AppError

# 免于限流的端点（试听流/进度轮询，与 Flask _QUIET/_rate_limit_guard 同口径）
_EXEMPT_PREFIXES = ('/audio_stream',)
_EXEMPT_PATHS = {'/api/queue', '/api/batch_progress', '/api/task/heartbeat'}


def client_ip(request: Request) -> str:
    """客户端 IP：仅当直连方是回环（可信反代）时采信 XFF/Real-IP，与 Flask 同策略。"""
    import auth_system
    remote = request.client.host if request.client else '-'
    if remote and remote != '-' and auth_system._is_loopback_ip(remote):
        xff = request.headers.get('x-forwarded-for')
        if xff:
            ip = auth_system._trusted_proxy_ip(xff)
            if ip and not auth_system._is_loopback_ip(ip):
                return ip
        xreal = request.headers.get('x-real-ip')
        if xreal:
            ip = auth_system._trusted_proxy_ip(xreal)
            if ip:
                return ip
    return remote or '-'


def rate_ok(key: str, limit: int, window: int) -> bool:
    """滑动窗口限流：True=放行。与 Flask main._rate_ok 同算法、同桶容器。"""
    now = time.time()
    with RATE_LOCK:
        dq = RATE_BUCKETS.get(key)
        if dq is None:
            if len(RATE_BUCKETS) > 8000:
                for k in [k for k, v in RATE_BUCKETS.items() if not v or now - v[-1] > window]:
                    RATE_BUCKETS.pop(k, None)
            dq = collections.deque()
            RATE_BUCKETS[key] = dq
        while dq and now - dq[0] > window:
            dq.popleft()
        if len(dq) >= limit:
            return False
        dq.append(now)
        return True


async def guard(request: Request, *, bucket: str, limit: int, window: int) -> None:
    """限流闸：超限抛 429（与 Flask 包体同形）。豁免端点直接放行。"""
    path = request.url.path
    if path in _EXEMPT_PATHS or path.startswith(_EXEMPT_PREFIXES):
        return
    if not rate_ok(f'{bucket}:' + client_ip(request), limit, window):
        raise AppError('请求过于频繁，请稍后再试', 429)