# flask_app/ConnectionLimiter.py

import threading
import logging
from functools import wraps
from flask import jsonify, request, Response, stream_with_context, current_app, g

# 配置模块级别的日志记录器
logger = logging.getLogger(__name__)

class ExecutionTimeoutMonitor:
    """监控请求执行时间，超时后释放信号量"""
    def __init__(self, timeout, semaphore, logger):
        self.timeout = timeout
        self.semaphore = semaphore
        self.is_timeout = False
        self.stopped = threading.Event()
        self.logger = logger
        self.thread = threading.Thread(target=self._monitor)
        self.thread.daemon = True

    def _monitor(self):
        """等待指定时间后标记为超时并释放信号量"""
        if not self.stopped.wait(self.timeout):
            self.is_timeout = True
            self.semaphore.release()  # 超时后释放信号量
            self.logger.error(f"请求执行时间超过 {self.timeout} 秒并被终止。")

    def start(self):
        self.thread.start()

    def stop(self):
        self.stopped.set()
        self.thread.join()

class ConnectionLimiter:
    def __init__(self, max_connections=10):
        self.semaphore = threading.Semaphore(max_connections)

#当请求超时时，连接资源（即信号量）会被释放，但是正在执行的程序不会被终止。这意味着虽然新的请求可以继续被接受和处理，但超时的请求仍然会在后台继续运行，直到完成或遇到其他中断条件。
def require_connection_limit(timeout=900):
    """装饰器：确保路由使用连接限制，并监控请求执行时间"""
    def decorator(f):
        @wraps(f)
        def wrapped(*args, **kwargs):
            # 统一获取 logger 对象
            logger_to_use = getattr(g, 'logger', logger)

            blueprint = request.blueprint
            limiter = current_app.connection_limiters.get(
                blueprint, current_app.connection_limiters.get('default'))
            if limiter is None:
                logger_to_use.error(
                    f"未为蓝图 '{blueprint}' 配置 ConnectionLimiter，并且未设置默认限流器。")
                return jsonify({'error': '服务器配置错误'}), 500

            acquired = limiter.semaphore.acquire(blocking=True)
            if not acquired:
                logger_to_use.warning("并发连接过多")
                return jsonify({'error': '并发连接过多'}), 429

            # 启动执行超时监控器
            monitor = ExecutionTimeoutMonitor(timeout, limiter.semaphore, logger_to_use)
            monitor.start()

            try:
                result = f(*args, **kwargs)

                if isinstance(result, Response):
                    # 对于 Response 对象，使用 call_on_close 释放信号量
                    def release_semaphore():
                        if not monitor.is_timeout:
                            limiter.semaphore.release()
                            monitor.stop()
                            logger_to_use.info("Response Object 正确释放")

                    result.call_on_close(release_semaphore)
                    return result

                elif hasattr(result, '__iter__') and not isinstance(result, (str, bytes)):
                    # 处理生成器响应
                    @stream_with_context
                    def generator_wrapper():
                        try:
                            for item in result:
                                if monitor.is_timeout:
                                    logger_to_use.error("请求执行时间超过限制并被终止。")
                                    break
                                yield item
                        except GeneratorExit:
                            # 客户端断开连接
                            logger_to_use.info("客户端断开连接")
                        finally:
                            if not monitor.is_timeout:
                                limiter.semaphore.release()
                                monitor.stop()
                                logger_to_use.info("在生成器的 finally 中释放信号量并停止监控器")
                    return Response(generator_wrapper(), mimetype='text/event-stream')
                else:
                    # 对于其他类型的响应，返回前释放信号量
                    if not monitor.is_timeout:
                        limiter.semaphore.release()
                        monitor.stop()
                        logger_to_use.info("Semaphore released for non-Response, non-generator result")
                    return result

            except Exception as e:
                if not monitor.is_timeout:
                    limiter.semaphore.release()
                    monitor.stop()
                logger_to_use.error(f"路由处理异常: {e}")
                return jsonify({'error': '内部服务器错误'}), 500

        return wrapped
    return decorator