import { Request, Response, NextFunction } from 'express'
import fs from 'fs'
import path from 'path'

// 日志目录
const LOG_DIR = path.resolve(process.env.LOG_DIR || './logs')
if (!fs.existsSync(LOG_DIR)) {
  fs.mkdirSync(LOG_DIR, { recursive: true })
}

/** 获取当前日期字符串 YYYY-MM-DD */
function getDateStr(): string {
  const d = new Date()
  return `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, '0')}-${String(d.getDate()).padStart(2, '0')}`
}

/** 格式化时间 HH:mm:ss.SSS */
function formatTime(date: Date): string {
  return `${String(date.getHours()).padStart(2, '0')}:${String(date.getMinutes()).padStart(2, '0')}:${String(date.getSeconds()).padStart(2, '0')}.${String(date.getMilliseconds()).padStart(3, '0')}`
}

/** 写入日志文件 */
function writeLog(level: string, message: string, meta?: Record<string, any>) {
  const dateStr = getDateStr()
  const logFile = path.join(LOG_DIR, `${dateStr}.log`)
  const now = new Date()
  const time = formatTime(now)
  const timestamp = now.toISOString() // 记录 UTC 时间戳，前端可按用户时区显示
  const metaStr = meta ? ` ${JSON.stringify(meta)}` : ''
  const line = `[${time}] [${timestamp}] ${level} ${message}${metaStr}\n`

  fs.appendFile(logFile, line, (err) => {
    if (err) console.error('[Logger] Write error:', err)
  })
}

/** 请求日志中间件 */
export function requestLogger(req: Request, res: Response, next: NextFunction) {
  const startTime = Date.now()
  const { method, url, ip } = req

  // 响应结束时记录日志（此时 authMiddleware 已执行，userId 可用）
  res.on('finish', () => {
    const duration = Date.now() - startTime
    const { statusCode } = res
    // 延迟获取 userId，确保 authMiddleware 已执行
    const userId = (req as any).userId

    const meta = {
      method,
      url,
      status: statusCode,
      duration: `${duration}ms`,
      ip: ip || req.headers['x-forwarded-for'] || 'unknown',
      userId: userId || null,
      userAgent: req.headers['user-agent']?.slice(0, 100) || ''
    }

    if (statusCode >= 400) {
      writeLog('ERROR', `${method} ${url} ${statusCode} ${duration}ms`, meta)
    } else if (duration > 1000) {
      writeLog('WARN', `Slow request: ${method} ${url} ${duration}ms`, meta)
    } else {
      writeLog('INFO', `${method} ${url} ${statusCode} ${duration}ms`, meta)
    }
  })

  next()
}

/** 错误日志 */
export function logError(message: string, error: Error | any, meta?: Record<string, any>) {
  writeLog('ERROR', message, {
    ...meta,
    error: error?.message || String(error),
    stack: error?.stack?.slice(0, 500) || ''
  })
}

/** 业务日志 */
export function logInfo(message: string, meta?: Record<string, any>) {
  writeLog('INFO', message, meta)
}

export default { requestLogger, logError, logInfo }