# coding=utf-8
"""
应用 API 限流中间件
基于滑动窗口算法实现 API 调用限流
"""
import time
from collections import defaultdict
from django.http import JsonResponse
from django.utils.deprecation import MiddlewareMixin
from common.utils.logger import maxkb_logger


class RateLimitMiddleware(MiddlewareMixin):
    """
    应用 API 限流中间件

    使用内存中的滑动窗口算法实现限流
    适用于单实例部署场景
    """

    def __init__(self, get_response=None):
        super().__init__(get_response)
        # 内存存储：{app_id: [(timestamp, count)]}
        self._requests = defaultdict(list)
        self._last_cleanup = time.time()

    def process_request(self, request):
        """
        处理请求限流检查
        """
        # 只对应用 API 进行限流检查
        path = request.path
        if not self._is_app_api(path):
            return None

        # 获取应用 ID
        app_id = self._extract_app_id(path, request)
        if not app_id:
            return None

        # 获取或创建限流配置
        rate_config = self._get_rate_config(app_id)
        if not rate_config or not rate_config.get('is_enabled'):
            return None

        # 检查是否超过限流
        client_ip = self._get_client_ip(request)
        is_limited = self._check_rate_limit(
            app_id,
            rate_config['max_requests'],
            rate_config['window_seconds']
        )

        if is_limited:
            maxkb_logger.warning(
                f"Rate limit exceeded for app {app_id} from {client_ip}"
            )
            return JsonResponse({
                'code': 429,
                'message': '请求过于频繁，请稍后再试',
                'data': {
                    'retry_after': rate_config.get('window_seconds', 60)
                }
            }, status=429)

        # 记录请求
        self._record_request(app_id, client_ip, path)

        return None

    def _is_app_api(self, path: str) -> bool:
        """判断是否为应用 API"""
        return '/api/workspace/' in path and '/application/' in path

    def _extract_app_id(self, path: str, request) -> str:
        """从路径或请求中提取应用 ID"""
        # 尝试从路径中提取
        parts = path.split('/')
        for i, part in enumerate(parts):
            if part == 'application' and i + 1 < len(parts):
                return parts[i + 1]
        return None

    def _get_client_ip(self, request) -> str:
        """获取客户端 IP"""
        x_forwarded_for = request.META.get('HTTP_X_FORWARDED_FOR')
        if x_forwarded_for:
            return x_forwarded_for.split(',')[0].strip()
        return request.META.get('REMOTE_ADDR', '')

    def _get_rate_config(self, app_id: str) -> dict:
        """
        获取应用的限流配置
        从数据库查询，实际生产中应使用缓存
        """
        try:
            from application.models.rate_limit import RateLimit
            from application.models.application import Application

            try:
                application = Application.objects.get(id=app_id)
            except Application.DoesNotExist:
                return None

            try:
                rate_limit = RateLimit.objects.get(application=application)
                return {
                    'is_enabled': rate_limit.is_enabled,
                    'max_requests': rate_limit.max_requests,
                    'window_seconds': rate_limit.window_seconds,
                }
            except RateLimit.DoesNotExist:
                return None

        except Exception as e:
            maxkb_logger.error(f"Failed to get rate config: {e}")
            return None

    def _check_rate_limit(self, app_id: str, max_requests: int,
                          window_seconds: int) -> bool:
        """
        检查是否超过限流
        使用滑动窗口算法
        """
        now = time.time()
        window_start = now - window_seconds

        # 清理过期记录
        self._requests[app_id] = [
            ts for ts in self._requests[app_id]
            if ts > window_start
        ]

        # 检查是否超过限制
        return len(self._requests[app_id]) >= max_requests

    def _record_request(self, app_id: str, client_ip: str, path: str):
        """记录请求"""
        now = time.time()
        self._requests[app_id].append(now)

        # 定期清理过期数据
        if now - self._last_cleanup > 300:  # 5分钟清理一次
            self._cleanup_old_requests()
            self._last_cleanup = now

    def _cleanup_old_requests(self):
        """清理所有过期的请求记录"""
        now = time.time()
        for app_id in list(self._requests.keys()):
            self._requests[app_id] = [
                ts for ts in self._requests[app_id]
                if now - ts < 3600  # 保留1小时内的记录
            ]
            if not self._requests[app_id]:
                del self._requests[app_id]