"""中间件模块"""
import asyncio
import logging
from starlette.middleware.base import BaseHTTPMiddleware
from starlette.requests import Request
from starlette.responses import Response
from config import MAX_CONCURRENT_REQUESTS

logger = logging.getLogger(__name__)


class ConcurrencyLimitMiddleware(BaseHTTPMiddleware):
    """并发限制中间件 - 防止内存爆炸"""
    
    def __init__(self, app, max_concurrent: int = MAX_CONCURRENT_REQUESTS):
        super().__init__(app)
        self.semaphore = asyncio.Semaphore(max_concurrent)
        self.max_concurrent = max_concurrent
        logger.info(f"并发限制中间件已启用，最大并发数：{max_concurrent}")
    
    async def dispatch(self, request: Request, call_next) -> Response:
        """处理请求"""
        async with self.semaphore:
            try:
                response = await call_next(request)
                return response
            except Exception as e:
                logger.error(f"请求处理错误: {e}", exc_info=True)
                return Response(
                    content='{"error": "Internal Server Error"}',
                    status_code=500,
                    media_type="application/json"
                )