"""
请求频率限制中间件
防止API被滥用和攻击
"""
from flask import request, jsonify, current_app
from functools import wraps
import time
import hashlib
from typing import Dict, Optional
import redis
import os


class RateLimiter:
    """频率限制器"""

    def __init__(self):
        self.redis_client = None
        self._init_redis()

    def _init_redis(self):
        """初始化Redis连接"""
        try:
            redis_url = os.environ.get('REDIS_URL')
            if redis_url:
                self.redis_client = redis.from_url(redis_url)
        except Exception as e:
            current_app.logger.warning(f"Redis连接失败，将使用内存存储: {str(e)}")
            self.redis_client = None

    def _get_client_ip(self) -> str:
        """获取客户端IP地址"""
        # 优先使用X-Forwarded-For头部（如果存在）
        if request.headers.get('X-Forwarded-For'):
            return request.headers.get('X-Forwarded-For').split(',')[0].strip()
        return request.remote_addr or '0.0.0.0'

    def _make_key(self, identifier: str, window: str) -> str:
        """生成Redis键"""
        return f"rate_limit:{identifier}:{window}"

    def check_rate_limit(
        self,
        identifier: Optional[str] = None,
        limit: int = 100,
        window: int = 3600
    ) -> Tuple[bool, Dict]:
        """
        检查频率限制
        :param identifier: 标识符（IP或用户ID）
        :param limit: 限制次数
        :param window: 时间窗口（秒）
        :return: (是否允许, 限制信息)
        """
        if not identifier:
            identifier = self._get_client_ip()

        current_time = int(time.time())
        window_size = window

        # 计算当前窗口
        current_window = current_time // window_size

        if self.redis_client:
            # 使用Redis存储
            key = self._make_key(identifier, current_window)
            pipe = self.redis_client.pipeline()
            pipe.incr(key)
            pipe.expire(key, window_size)
            results = pipe.execute()

            current_requests = results[0]
        else:
            # 使用内存存储（仅用于开发环境）
            key = self._make_key(identifier, current_window)
            if not hasattr(current_app, '_rate_limits'):
                current_app._rate_limits = {}

            if key not in current_app._rate_limits:
                current_app._rate_limits[key] = {
                    'count': 1,
                    'expire': current_time + window_size
                }
            else:
                # 检查是否过期
                if current_app._rate_limits[key]['expire'] < current_time:
                    current_app._rate_limits[key] = {
                        'count': 1,
                        'expire': current_time + window_size
                    }
                else:
                    current_app._rate_limits[key]['count'] += 1

            current_requests = current_app._rate_limits[key]['count']

        # 检查是否超过限制
        remaining = max(0, limit - current_requests)
        reset_time = (current_window + 1) * window_size

        allowed = current_requests <= limit

        return allowed, {
            'limit': limit,
            'remaining': remaining,
            'reset': reset_time,
            'current': current_requests
        }


# 全局实例
rate_limiter = RateLimiter()


def rate_limit(limit: int = 100, window: int = 3600, key_func=None):
    """
    频率限制装饰器
    :param limit: 限制次数
    :param window: 时间窗口（秒）
    :param key_func: 自定义键生成函数
    """
    def decorator(f):
        @wraps(f)
        def decorated_function(*args, **kwargs):
            # 生成标识符
            identifier = None
            if key_func:
                identifier = key_func()

            # 检查频率限制
            allowed, info = rate_limiter.check_rate_limit(identifier, limit, window)

            if not allowed:
                # 添加限制信息到响应头
                response = jsonify({
                    'success': False,
                    'message': '请求过于频繁，请稍后再试',
                    'rate_limit': info
                })
                response.status_code = 429
                response.headers['X-RateLimit-Limit'] = str(info['limit'])
                response.headers['X-RateLimit-Remaining'] = str(info['remaining'])
                response.headers['X-RateLimit-Reset'] = str(info['reset'])
                return response

            # 如果允许，执行函数
            result = f(*args, **kwargs)

            # 添加限制信息到响应头
            if hasattr(result, 'headers'):
                result.headers['X-RateLimit-Limit'] = str(info['limit'])
                result.headers['X-RateLimit-Remaining'] = str(info['remaining'])
                result.headers['X-RateLimit-Reset'] = str(info['reset'])

            return result
        return decorated_function
    return decorator


def ip_key() -> str:
    """基于IP的键"""
    return rate_limiter._get_client_ip()


def user_key() -> str:
    """基于用户ID的键"""
    from flask_login import current_user
    if hasattr(current_user, 'is_authenticated') and current_user.is_authenticated:
        return f"user:{current_user.get_id()}"
    return ip_key()