llm-chat/backend/middleware/logger.js

const morgan = require('morgan');
const fs = require('fs');
const path = require('path');

// 创建日志目录
const logDir = path.join(__dirname, '../logs');
if (!fs.existsSync(logDir)) {
  fs.mkdirSync(logDir, { recursive: true });
}

// 自定义日志格式
const customFormat = ':remote-addr - :remote-user [:date[clf]] ":method :url HTTP/:http-version" :status :res[content-length] ":referrer" ":user-agent" :response-time ms';

// 创建访问日志流
const accessLogStream = fs.createWriteStream(
  path.join(logDir, 'access.log'), 
  { flags: 'a' }
);

// 创建错误日志流
const errorLogStream = fs.createWriteStream(
  path.join(logDir, 'error.log'), 
  { flags: 'a' }
);

/**
 * 请求日志中间件
 */
const requestLogger = morgan(customFormat, {
  stream: accessLogStream,
  skip: (req, res) => {
    // 跳过健康检查请求的日志记录
    return req.url === '/api/health';
  }
});

/**
 * 控制台日志中间件（开发环境）
 */
const consoleLogger = morgan('dev', {
  skip: (req, res) => {
    // 生产环境跳过控制台日志
    return process.env.NODE_ENV === 'production';
  }
});

/**
 * 错误日志中间件
 */
const errorLogger = (err, req, res, next) => {
  const timestamp = new Date().toISOString();
  const errorLog = {
    timestamp,
    method: req.method,
    url: req.url,
    ip: req.ip,
    userAgent: req.get('User-Agent'),
    error: {
      name: err.name,
      message: err.message,
      stack: err.stack
    },
    body: req.body,
    params: req.params,
    query: req.query
  };

  // 写入错误日志文件
  errorLogStream.write(JSON.stringify(errorLog) + '\n');
  
  // 控制台输出（开发环境）
  if (process.env.NODE_ENV !== 'production') {
    console.error('错误日志:', errorLog);
  }

  next(err);
};

/**
 * 自定义日志记录器
 */
class Logger {
  static info(message, data = {}) {
    const logEntry = {
      level: 'INFO',
      timestamp: new Date().toISOString(),
      message,
      data
    };
    
    console.log('[INFO]', message, data);
    
    // 可选：写入日志文件
    if (process.env.NODE_ENV === 'production') {
      const infoLogStream = fs.createWriteStream(
        path.join(logDir, 'app.log'), 
        { flags: 'a' }
      );
      infoLogStream.write(JSON.stringify(logEntry) + '\n');
    }
  }

  static warn(message, data = {}) {
    const logEntry = {
      level: 'WARN',
      timestamp: new Date().toISOString(),
      message,
      data
    };
    
    console.warn('[WARN]', message, data);
    
    if (process.env.NODE_ENV === 'production') {
      const warnLogStream = fs.createWriteStream(
        path.join(logDir, 'app.log'), 
        { flags: 'a' }
      );
      warnLogStream.write(JSON.stringify(logEntry) + '\n');
    }
  }

  static error(message, error = {}, data = {}) {
    const logEntry = {
      level: 'ERROR',
      timestamp: new Date().toISOString(),
      message,
      error: {
        name: error.name,
        message: error.message,
        stack: error.stack
      },
      data
    };
    
    console.error('[ERROR]', message, error, data);
    
    errorLogStream.write(JSON.stringify(logEntry) + '\n');
  }

  static debug(message, data = {}) {
    if (process.env.NODE_ENV === 'development') {
      console.debug('[DEBUG]', message, data);
    }
  }
}

/**
 * API调用统计中间件
 */
const apiStats = (() => {
  const stats = {
    totalRequests: 0,
    endpoints: {},
    methods: {},
    statusCodes: {},
    averageResponseTime: 0,
    startTime: Date.now()
  };

  return (req, res, next) => {
    const startTime = Date.now();
    
    // 记录请求开始
    stats.totalRequests++;
    
    const endpoint = req.route?.path || req.path;
    const method = req.method;
    
    stats.endpoints[endpoint] = (stats.endpoints[endpoint] || 0) + 1;
    stats.methods[method] = (stats.methods[method] || 0) + 1;

    // 监听响应结束
    res.on('finish', () => {
      const responseTime = Date.now() - startTime;
      const statusCode = res.statusCode;
      
      stats.statusCodes[statusCode] = (stats.statusCodes[statusCode] || 0) + 1;
      
      // 更新平均响应时间
      if (stats.averageResponseTime === 0) {
        stats.averageResponseTime = responseTime;
      } else {
        stats.averageResponseTime = (stats.averageResponseTime + responseTime) / 2;
      }
    });

    next();
  };
})();

/**
 * 获取API统计信息
 */
const getApiStats = () => {
  const uptime = Date.now() - apiStats.startTime;
  return {
    ...apiStats,
    uptime,
    uptimeHuman: formatUptime(uptime)
  };
};

/**
 * 格式化运行时间
 */
function formatUptime(ms) {
  const seconds = Math.floor(ms / 1000);
  const minutes = Math.floor(seconds / 60);
  const hours = Math.floor(minutes / 60);
  const days = Math.floor(hours / 24);

  if (days > 0) return `${days}天${hours % 24}小时${minutes % 60}分钟`;
  if (hours > 0) return `${hours}小时${minutes % 60}分钟`;
  if (minutes > 0) return `${minutes}分钟${seconds % 60}秒`;
  return `${seconds}秒`;
}

module.exports = {
  requestLogger,
  consoleLogger,
  errorLogger,
  apiStats,
  getApiStats,
  Logger
};