text: 'use strict'
  
  require('./check-versions')()
  
  const config = require('../config')
  if (!process.env.NODE_ENV) {
    process.env.NODE_ENV = JSON.parse(config.dev.env.NODE_ENV)
  }
  
  const opn = require('opn')
  const path = require('path')
  const express = require('express')
  const webpack = require('webpack')
  const proxyMiddleware = require('http-proxy-middleware')
  const webpackConfig = process.env.NODE_ENV === 'testing'
    ? require('./webpack.prod.conf')
    : require('./webpack.dev.conf')
  
  // default port where dev server listens for incoming traffic
  const port = process.env.PORT || config.dev.port
  // automatically open browser, if not set will be false
  const autoOpenBrowser = !!config.dev.autoOpenBrowser
  // Define HTTP proxies to your custom API backend
  // https://github.com/chimurai/http-proxy-middleware
  const proxyTable = config.dev.proxyTable
  
  const app = express()
  const compiler = webpack(webpackConfig)
  
  const devMiddleware = require('webpack-dev-middleware')(compiler, {
    publicPath: webpackConfig.output.publicPath,
    quiet: true
  })
  
  const hotMiddleware = require('webpack-hot-middleware')(compiler, {
    log: false
  })
  // force page reload when html-webpack-plugin template changes
  compiler.plugin('compilation', function (compilation) {
    compilation.plugin('html-webpack-plugin-after-emit', function (data, cb) {
      hotMiddleware.publish({ action: 'reload' })
      cb()
    })
  })
  
  // enable hot-reload and state-preserving
  // compilation error display
  app.use(hotMiddleware)
  
  // proxy api requests
  Object.keys(proxyTable).forEach(function (context) {
    let options = proxyTable[context]
    if (typeof options === 'string') {
      options = { target: options }
    }
    app.use(proxyMiddleware(options.filter || context, options))
  })
  
  // 此為 vue-template/webpack 預設開啟功能，但 GitHub page 不支援)
  // handle fallback for HTML5 history API
  app.use(require('connect-history-api-fallback')())
  
  // serve webpack bundle output
  app.use(devMiddleware)
  
  // serve pure static assets
  const staticPath = path.posix.join(config.dev.assetsPublicPath, config.dev.assetsSubDirectory)
  app.use(staticPath, express.static('./static'))
  const _404path = path.posix.join(config.dev.assetsPublicPath, '404.html')
  app.use(_404path, express.static('./404.html'))
  
  const uri = 'http://localhost:' + port
  
  let _resolve
  const readyPromise = new Promise(resolve => {
    _resolve = resolve
  })
  
  console.log('> Starting dev server...')
  devMiddleware.waitUntilValid(() => {
    console.log('> Listening at ' + uri + '\n')
    // when env is testing, don't need open it
    if (autoOpenBrowser && process.env.NODE_ENV !== 'testing') {
      opn(uri)
    }
    _resolve()
  })
  
  // 剩下的 path 回傳 404.html（仿 GitHub Page 機制）
  app.get('*', function (req, res) {
    res.status(404).sendFile(path.resolve(__dirname, '../404.html'));
  });
  
  const server = app.listen(port)
  
  module.exports = {
    ready: readyPromise,
    close: () => {
      server.close()
    }
  }
  