text: // Do this as the first thing so that any code reading it knows the right env.
  process.env.NODE_ENV = 'production';
  
  // Load environment variables from .env file. Suppress warnings using silent
  // if this file is missing. dotenv will never modify any environment variables
  // that have already been set.
  // https://github.com/motdotla/dotenv
  require('dotenv').config({silent: true});
  
  var chalk = require('chalk');
  var fs = require('fs-extra');
  var path = require('path');
  var url = require('url');
  var filesize = require('filesize');
  var gzipSize = require('gzip-size').sync;
  var webpack = require('webpack');
  var config = require('../config/webpack.config.prod');
  var paths = require('../config/paths');
  var checkRequiredFiles = require('react-dev-utils/checkRequiredFiles');
  var recursive = require('recursive-readdir');
  var stripAnsi = require('strip-ansi');
  
  var useYarn = fs.existsSync(paths.yarnLockFile);
  
  // Warn and crash if required files are missing
  if (!checkRequiredFiles([paths.appHtml, paths.appIndexJs])) {
    process.exit(1);
  }
  
  // Input: /User/dan/app/build/static/js/main.82be8.js
  // Output: /static/js/main.js
  function removeFileNameHash(fileName) {
    return fileName
      .replace(paths.appBuild, '')
      .replace(/\/?(.*)(\.\w+)(\.js|\.css)/, (match, p1, p2, p3) => p1 + p3);
  }
  
  // Input: 1024, 2048
  // Output: "(+1 KB)"
  function getDifferenceLabel(currentSize, previousSize) {
    var FIFTY_KILOBYTES = 1024 * 50;
    var difference = currentSize - previousSize;
    var fileSize = !Number.isNaN(difference) ? filesize(difference) : 0;
    if (difference >= FIFTY_KILOBYTES) {
      return chalk.red('+' + fileSize);
    } else if (difference < FIFTY_KILOBYTES && difference > 0) {
      return chalk.yellow('+' + fileSize);
    } else if (difference < 0) {
      return chalk.green(fileSize);
    } else {
      return '';
    }
  }
  
  // First, read the current file sizes in build directory.
  // This lets us display how much they changed later.
  recursive(paths.appBuild, (err, fileNames) => {
    var previousSizeMap = (fileNames || [])
      .filter(fileName => /\.(js|css)$/.test(fileName))
      .reduce((memo, fileName) => {
        var contents = fs.readFileSync(fileName);
        var key = removeFileNameHash(fileName);
        memo[key] = gzipSize(contents);
        return memo;
      }, {});
  
    // Remove all content but keep the directory so that
    // if you're in it, you don't end up in Trash
    fs.emptyDirSync(paths.appBuild);
  
    // Start the webpack build
    build(previousSizeMap);
  
    // Merge with the public folder
    copyPublicFolder();
  });
  
  // Print a detailed summary of build files.
  function printFileSizes(stats, previousSizeMap) {
    var assets = stats.toJson().assets
      .filter(asset => /\.(js|css)$/.test(asset.name))
      .map(asset => {
        var fileContents = fs.readFileSync(paths.appBuild + '/' + asset.name);
        var size = gzipSize(fileContents);
        var previousSize = previousSizeMap[removeFileNameHash(asset.name)];
        var difference = getDifferenceLabel(size, previousSize);
        return {
          folder: path.join('build', path.dirname(asset.name)),
          name: path.basename(asset.name),
          size: size,
          sizeLabel: filesize(size) + (difference ? ' (' + difference + ')' : '')
        };
      });
    assets.sort((a, b) => b.size - a.size);
    var longestSizeLabelLength = Math.max.apply(null,
      assets.map(a => stripAnsi(a.sizeLabel).length)
    );
    assets.forEach(asset => {
      var sizeLabel = asset.sizeLabel;
      var sizeLength = stripAnsi(sizeLabel).length;
      if (sizeLength < longestSizeLabelLength) {
        var rightPadding = ' '.repeat(longestSizeLabelLength - sizeLength);
        sizeLabel += rightPadding;
      }
      console.log(
        '  ' + sizeLabel +
        '  ' + chalk.dim(asset.folder + path.sep) + chalk.cyan(asset.name)
      );
    });
  }
  
  // Print out errors
  function printErrors(summary, errors) {
    console.log(chalk.red(summary));
    console.log();
    errors.forEach(err => {
      console.log(err.message || err);
      console.log();
    });
  }
  
  // Create the production build and print the deployment instructions.
  function build(previousSizeMap) {
    console.log('Creating an optimized production build...');
    webpack(config).run((err, stats) => {
      if (err) {
        printErrors('Failed to compile.', [err]);
        process.exit(1);
      }
  
      if (stats.compilation.errors.length) {
        printErrors('Failed to compile.', stats.compilation.errors);
        process.exit(1);
      }
  
      if (process.env.CI && stats.compilation.warnings.length) {
        printErrors('Failed to compile. When process.env.CI = true, warnings are treated as failures. Most CI servers set this automatically.', stats.compilation.warnings);
        process.exit(1);
      }
  
      console.log(chalk.green('Compiled successfully.'));
      console.log();
  
      console.log('File sizes after gzip:');
      console.log();
      printFileSizes(stats, previousSizeMap);
      console.log();
  
      var openCommand = process.platform === 'win32' ? 'start' : 'open';
      var appPackage  = require(paths.appPackageJson);
      var publicUrl = paths.publicUrl;
      var publicPath = config.output.publicPath;
      var publicPathname = url.parse(publicPath).pathname;
      if (publicUrl && publicUrl.indexOf('.github.io/') !== -1) {
        // "homepage": "http://user.github.io/project"
        console.log('The project was built assuming it is hosted at ' + chalk.green(publicPathname) + '.');
        console.log('You can control this with the ' + chalk.green('homepage') + ' field in your '  + chalk.cyan('package.json') + '.');
        console.log();
        console.log('The ' + chalk.cyan('build') + ' folder is ready to be deployed.');
        console.log('To publish it at ' + chalk.green(publicUrl) + ', run:');
        // If script deploy has been added to package.json, skip the instructions
        if (typeof appPackage.scripts.deploy === 'undefined') {
          console.log();
          if (useYarn) {
            console.log('  ' + chalk.cyan('yarn') +  ' add --dev gh-pages');
          } else {
            console.log('  ' + chalk.cyan('npm') +  ' install --save-dev gh-pages');
          }
          console.log();
          console.log('Add the following script in your ' + chalk.cyan('package.json') + '.');
          console.log();
          console.log('    ' + chalk.dim('// ...'));
          console.log('    ' + chalk.yellow('"scripts"') + ': {');
          console.log('      ' + chalk.dim('// ...'));
          console.log('      ' + chalk.yellow('"predeploy"') + ': ' + chalk.yellow('"npm run build",'));
          console.log('      ' + chalk.yellow('"deploy"') + ': ' + chalk.yellow('"gh-pages -d build"'));
          console.log('    }');
          console.log();
          console.log('Then run:');
        }
        console.log();
        console.log('  ' + chalk.cyan(useYarn ? 'yarn' : 'npm') +  ' run deploy');
        console.log();
      } else if (publicPath !== '/') {
        // "homepage": "http://mywebsite.com/project"
        console.log('The project was built assuming it is hosted at ' + chalk.green(publicPath) + '.');
        console.log('You can control this with the ' + chalk.green('homepage') + ' field in your '  + chalk.cyan('package.json') + '.');
        console.log();
        console.log('The ' + chalk.cyan('build') + ' folder is ready to be deployed.');
        console.log();
      } else {
        if (publicUrl) {
          // "homepage": "http://mywebsite.com"
          console.log('The project was built assuming it is hosted at ' + chalk.green(publicUrl) +  '.');
          console.log('You can control this with the ' + chalk.green('homepage') + ' field in your '  + chalk.cyan('package.json') + '.');
          console.log();
        } else {
          // no homepage
          console.log('The project was built assuming it is hosted at the server root.');
          console.log('To override this, specify the ' + chalk.green('homepage') + ' in your '  + chalk.cyan('package.json') + '.');
          console.log('For example, add this to build it for GitHub Pages:')
          console.log();
          console.log('  ' + chalk.green('"homepage"') + chalk.cyan(': ') + chalk.green('"http://myname.github.io/myapp"') + chalk.cyan(','));
          console.log();
        }
        console.log('The ' + chalk.cyan('build') + ' folder is ready to be deployed.');
        console.log('You may also serve it locally with a static server:')
        console.log();
        if (useYarn) {
          console.log('  ' + chalk.cyan('yarn') +  ' global add pushstate-server');
        } else {
          console.log('  ' + chalk.cyan('npm') +  ' install -g pushstate-server');
        }
        console.log('  ' + chalk.cyan('pushstate-server') + ' build');
        console.log('  ' + chalk.cyan(openCommand) + ' http://localhost:9000');
        console.log();
      }
    });
  }
  
  function copyPublicFolder() {
    fs.copySync(paths.appPublic, paths.appBuild, {
      dereference: true,
      filter: file => file !== paths.appHtml
    });
  }
  