'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.log(
     chalk.cyan(
       `Attempting to bind to HOST environment variable: ${chalk.yellow(
         chalk.bold(process.env.HOST)
       )}`
     )
   );
   console.log(
     `If this was unintentional, check that you haven't mistakenly set it in your shell.`
   );
   console.log(`Learn more here: ${chalk.yellow('http://bit.ly/2mwWSwH')}`);
   console.log();
 }
 
 // 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.log(err);
       }
       if (isInteractive) {
         clearConsole();
       }
       console.log(chalk.cyan('Starting the development server...\n'));
       openBrowser(urls.localUrlForBrowser);
     });
 
     ['SIGINT', 'SIGTERM'].forEach(function(sig) {
       process.on(sig, function() {
         devServer.close();
         process.exit();
       });
     });
   })
   .catch(err => {
     if (err && err.message) {
       console.log(err.message);
     }
     process.exit(1);
   });