text: const chokidar = require('chokidar')
  const bodyParser = require('body-parser')
  const chalk = require('chalk')
  const path = require('path')
  
  const mockDir = path.join(process.cwd(), 'mock')
  
  function registerRoutes(app) {
    let mockLastIndex
    const { default: mocks } = require('./index.js')
    for (const mock of mocks) {
      app[mock.type](mock.url, mock.response)
      mockLastIndex = app._router.stack.length
    }
    const mockRoutesLength = Object.keys(mocks).length
    return {
      mockRoutesLength: mockRoutesLength,
      mockStartIndex: mockLastIndex - mockRoutesLength
    }
  }
  
  function unregisterRoutes() {
    Object.keys(require.cache).forEach(i => {
      if (i.includes(mockDir)) {
        delete require.cache[require.resolve(i)]
      }
    })
  }
  
  module.exports = app => {
    // es6 polyfill
    require('@babel/register')
  
    // parse app.body
    // https://expressjs.com/en/4x/api.html#req.body
    app.use(bodyParser.json())
    app.use(
      bodyParser.urlencoded({
        extended: true
      })
    )
  
    const mockRoutes = registerRoutes(app)
    var mockRoutesLength = mockRoutes.mockRoutesLength
    var mockStartIndex = mockRoutes.mockStartIndex
  
    // watch files, hot  mock server
    chokidar
      .watch(mockDir, {
        ignored: /mock-server/,
        ignoreInitial: true
      })
      .on('all', (event, path) => {
        if (event === 'change' || event === 'add') {
          try {
            // remove mock routes stack
            app._router.stack.splice(mockStartIndex, mockRoutesLength)
  
            // clear routes cache
            unregisterRoutes()
  
            const mockRoutes = registerRoutes(app)
            mockRoutesLength = mockRoutes.mockRoutesLength
            mockStartIndex = mockRoutes.mockStartIndex
  
            console.log(
              chalk.magentaBright(
                `\n > Mock Server hot  success! changed  ${path}`
              )
            )
          } catch (error) {
            console.log(chalk.redBright(error))
          }
        }
      })
  }
  