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

/**
 * 日志级别
 */
const LOG_LEVELS = {
  debug: 0,
  info: 1,
  warn: 2,
  error: 3
}

/**
 * 日志器
 */
class Logger {
  constructor(level = 'info', logDir = './logs') {
    this.level = LOG_LEVELS[level] || LOG_LEVELS.info
    this.logDir = logDir
    
    // 确保日志目录存在
    if (!fs.existsSync(logDir)) {
      fs.mkdirSync(logDir, { recursive: true })
    }
  }
  
  /**
   * 格式化日志消息
   */
  formatMessage(level, message, meta = {}) {
    const timestamp = new Date().toISOString()
    const metaStr = Object.keys(meta).length > 0 ? JSON.stringify(meta) : ''
    return `[${timestamp}] [${level.toUpperCase()}] ${message} ${metaStr}\n`
  }
  
  /**
   * 写入日志文件
   */
  writeToFile(level, message, meta) {
    const date = new Date().toISOString().split('T')[0]
    const logFile = path.join(this.logDir, `${date}.log`)
    const logMessage = this.formatMessage(level, message, meta)
    
    fs.appendFile(logFile, logMessage, (err) => {
      if (err) console.error('写入日志失败:', err)
    })
  }
  
  /**
   * 记录日志
   */
  log(level, message, meta = {}) {
    if (LOG_LEVELS[level] < this.level) return
    
    const formattedMessage = this.formatMessage(level, message, meta)
    
    // 控制台输出
    switch (level) {
      case 'error':
        console.error(formattedMessage.trim())
        break
      case 'warn':
        console.warn(formattedMessage.trim())
        break
      default:
        console.log(formattedMessage.trim())
    }
    
    // 文件输出（生产环境）
    if (process.env.NODE_ENV === 'production') {
      this.writeToFile(level, message, meta)
    }
  }
  
  debug(message, meta) {
    this.log('debug', message, meta)
  }
  
  info(message, meta) {
    this.log('info', message, meta)
  }
  
  warn(message, meta) {
    this.log('warn', message, meta)
  }
  
  error(message, meta) {
    this.log('error', message, meta)
  }
}

// 导出单例
const logger = new Logger(process.env.LOG_LEVEL || 'info')

module.exports = logger