"""性能监控中间件

记录请求响应时间，用于性能分析和优化
"""

import time
import logging
from typing import Callable

from fastapi import Request, Response
from starlette.middleware.base import BaseHTTPMiddleware

logger = logging.getLogger(__name__)


class PerformanceMiddleware(BaseHTTPMiddleware):
    """性能监控中间件
    
    记录每个请求的响应时间，并在响应头中添加 X-Response-Time
    """
    
    # 慢请求阈值（毫秒）
    SLOW_REQUEST_THRESHOLD = 1000
    
    async def dispatch(self, request: Request, call_next: Callable) -> Response:
        start_time = time.time()
        
        # 执行请求
        response = await call_next(request)
        
        # 计算响应时间
        process_time = (time.time() - start_time) * 1000
        
        # 添加响应头
        response.headers["X-Response-Time"] = f"{process_time:.2f}ms"
        
        # 记录慢请求
        if process_time > self.SLOW_REQUEST_THRESHOLD:
            logger.warning(
                f"Slow request: {request.method} {request.url.path} "
                f"took {process_time:.2f}ms"
            )
        
        # 记录请求日志（开发环境）
        logger.debug(
            f"{request.method} {request.url.path} - "
            f"{response.status_code} - {process_time:.2f}ms"
        )
        
        return response