text: "use strict"
  
  // Do this as the first thing so that any code reading it knows the right env.
  process.env.BABEL_ENV = "development"
  process.env.NODE_ENV = "development"
  
  // Makes the script crash on unhandled rejections instead of silently
  // ignoring them. In the future, promise rejections that are not handled will
  // terminate the Node.js process with a non-zero exit code.
  process.on("unhandledRejection", err => {
    throw err
  })
  
  // Ensure environment variables are read.
  require("../config/env")
  
  const fs = require("fs")
  const chalk = require("chalk")
  const webpack = require("webpack")
  const WebpackDevServer = require("webpack-dev-server")
  const clearConsole = require("react-dev-utils/clearConsole")
  const checkRequiredFiles = require("react-dev-utils/checkRequiredFiles")
  const {
    choosePort,
    createCompiler,
    prepareProxy,
    prepareUrls
  } = require("react-dev-utils/WebpackDevServerUtils")
  const openBrowser = require("react-dev-utils/openBrowser")
  const paths = require("../config/paths")
  const config = require("../config/webpack.config.dev")
  const createDevServerConfig = require("../config/webpackDevServer.config")
  
  const useYarn = fs.existsSync(paths.yarnLockFile)
  const isInteractive = process.stdout.isTTY
  
  // Warn and crash if required files are missing
  if (!checkRequiredFiles([paths.appHtml, paths.appIndexJs])) {
    process.exit(1)
  }
  
  // Tools like Cloud9 rely on this.
  const DEFAULT_PORT = parseInt(process.env.PORT, 10) || 3000
  const HOST = process.env.HOST || "0.0.0.0"
  
  if (process.env.HOST) {
    console.info(
      chalk.cyan(
        `Attempting to bind to HOST environment variable: ${chalk.yellow(
          chalk.bold(process.env.HOST)
        )}`
      )
    )
    console.info(
      `If this was unintentional, check that you haven't mistakenly set it in your shell.`
    )
    console.info(`Learn more here: ${chalk.yellow("http://bit.ly/2mwWSwH")}`)
  }
  
  // We attempt to use the default port but if it is busy, we offer the user to
  // run on a different port. `choosePort()` Promise resolves to the next free port.
  choosePort(HOST, DEFAULT_PORT)
    .then(port => {
      if (port == null) {
        // We have not found a port.
        return
      }
      const protocol = process.env.HTTPS === "true" ? "https" : "http"
      const appName = require(paths.appPackageJson).name
      const urls = prepareUrls(protocol, HOST, port)
      // Create a webpack compiler that is configured with custom messages.
      const compiler = createCompiler(webpack, config, appName, urls, useYarn)
      // Load proxy config
      const proxySetting = require(paths.appPackageJson).proxy
      const proxyConfig = prepareProxy(proxySetting, paths.appPublic)
      // Serve webpack assets generated by the compiler over a web sever.
      const serverConfig = createDevServerConfig(
        proxyConfig,
        urls.lanUrlForConfig
      )
      const devServer = new WebpackDevServer(compiler, serverConfig)
      // Launch WebpackDevServer.
      devServer.listen(port, HOST, err => {
        if (err) {
          return console.info(err)
        }
        if (isInteractive) {
          clearConsole()
        }
        console.info(chalk.cyan("Starting the development server...\n"))
        openBrowser(urls.localUrlForBrowser)
      })
  
      ;["SIGINT", "SIGTERM"].forEach((sig) => {
        process.on(sig, () => {
          devServer.close()
          process.exit()
        })
      })
    })
    .catch(err => {
      if (err && err.message) {
        console.info(err.message)
      }
      process.exit(1)
    })
  