/**
 * 静态资源中间件 - 简化版本
 */
import fs from 'fs'
import NPath from 'path'
import { promisify } from 'util'

const stat = promisify(fs.stat)

export default function staticMiddleware(ctx, path, options = {}) {
  const { 
    root,
    maxAge = 0,
    immutable = false 
  } = options

  return new Promise(async (resolve, reject) => {
    try {
      const fullPath = NPath.resolve(root, path.startsWith('/') ? path.slice(1) : path)

      // 检查文件是否存在
      const stats = await stat(fullPath)
      
      if (!stats.isFile()) {
        return resolve() // reject(new Error('Not a file'))
      }

      // 设置响应头
      ctx.set('Content-Length', stats.size)
      ctx.set('Last-Modified', stats.mtime.toUTCString())
      
      const directives = [`max-age=${Math.floor(maxAge / 1000)}`]
      if (immutable) directives.push('immutable')
      ctx.set('Cache-Control', directives.join(','))
      
      // 设置内容类型
      const ext = NPath.extname(fullPath)
      if (ext) {
        ctx.type = ext
      }
      
      // 发送文件
      ctx.body = fs.createReadStream(fullPath)
      resolve(fullPath)
      
    } catch (err) {
      if (err.code === 'ENOENT') {
        err.status = 404
      }
      reject(err)
    }
  })
}