text: 'use strict';
  
  const autoprefixer = require('autoprefixer');
  const path = require('path');
  const webpack = require('webpack');
  const HtmlWebpackPlugin = require('html-webpack-plugin');
  const ExtractTextPlugin = require('extract-text-webpack-plugin');
  const ManifestPlugin = require('webpack-manifest-plugin');
  const InterpolateHtmlPlugin = require('react-dev-utils/InterpolateHtmlPlugin');
  const SWPrecacheWebpackPlugin = require('sw-precache-webpack-plugin');
  const eslintFormatter = require('react-dev-utils/eslintFormatter');
  const ModuleScopePlugin = require('react-dev-utils/ModuleScopePlugin');
  const paths = require('./paths');
  const getClientEnvironment = require('./env');
  
  // Webpack uses `publicPath` to determine where the app is being served from.
  // It requires a trailing slash, or the file assets will get an incorrect path.
  const publicPath = paths.servedPath;
  // Some apps do not use client-side routing with pushState.
  // For these, "homepage" can be set to "." to enable relative asset paths.
  const shouldUseRelativeAssetPaths = publicPath === './';
  // Source maps are resource heavy and can cause out of memory issue for large source files.
  const shouldUseSourceMap = process.env.GENERATE_SOURCEMAP !== 'false';
  // `publicUrl` is just like `publicPath`, but we will provide it to our app
  // as %PUBLIC_URL% in `index.html` and `process.env.PUBLIC_URL` in JavaScript.
  // Omit trailing slash as %PUBLIC_URL%/xyz looks better than %PUBLIC_URL%xyz.
  const publicUrl = publicPath.slice(0, -1);
  // Get environment variables to inject into our app.
  const env = getClientEnvironment(publicUrl);
  
  // Assert this just to be safe.
  // Development builds of React are slow and not intended for production.
  if (env.stringified['process.env'].NODE_ENV !== '"production"') {
      throw new Error('Production builds must have NODE_ENV=production.');
  }
  
  // Note: defined here because it will be used more than once.
  const cssFilename = 'static/css/[name].[contenthash:8].css';
  
  // ExtractTextPlugin expects the build output to be flat.
  // (See https://github.com/webpack-contrib/extract-text-webpack-plugin/issues/27)
  // However, our output is structured with css, js and media folders.
  // To have this structure working with relative paths, we have to use custom options.
  const extractTextPluginOptions = shouldUseRelativeAssetPaths
      ? // Making sure that the publicPath goes back to to build folder.
        { publicPath: Array(cssFilename.split('/').length).join('../') }
      : {};
  
  // This is the production configuration.
  // It compiles slowly and is focused on producing a fast and minimal bundle.
  // The development configuration is different and lives in a separate file.
  module.exports = {
      // Don't attempt to continue if there are any errors.
      bail: true,
      // We generate sourcemaps in production. This is slow but gives good results.
      // You can exclude the *.map files from the build during deployment.
      devtool: shouldUseSourceMap ? 'source-map' : false,
      // In production, we only want to load the polyfills and the app code.
      entry: [require.resolve('./polyfills'), paths.appIndexJs],
      output: {
          // The build folder.
          path: paths.appBuild,
          // Generated JS file names (with nested folders).
          // There will be one main bundle, and one file per asynchronous chunk.
          // We don't currently advertise code splitting but Webpack supports it.
          filename: 'static/js/[name].[chunkhash:8].js',
          chunkFilename: 'static/js/[name].[chunkhash:8].chunk.js',
          // We inferred the "public path" (such as / or /my-project) from homepage.
          publicPath: publicPath,
          // Point sourcemap entries to original disk location (format as URL on Windows)
          devtoolModuleFilenameTemplate: info =>
              path.relative(paths.appSrc, info.absoluteResourcePath).replace(/\\/g, '/'),
      },
      resolve: {
          // This allows you to set a fallback for where Webpack should look for modules.
          // We placed these paths second because we want `node_modules` to "win"
          // if there are any conflicts. This matches Node resolution mechanism.
          // https://github.com/facebookincubator/create-react-app/issues/253
          modules: ['node_modules', paths.appNodeModules].concat(
              // It is guaranteed to exist because we tweak it in `env.js`
              process.env.NODE_PATH.split(path.delimiter).filter(Boolean)
          ),
          // These are the reasonable defaults supported by the Node ecosystem.
          // We also include JSX as a common component filename extension to support
          // some tools, although we do not recommend using it, see:
          // https://github.com/facebookincubator/create-react-app/issues/290
          // `web` extension prefixes have been added for better support
          // for React Native Web.
          extensions: ['.web.js', '.mjs', '.js', '.json', '.web.jsx', '.jsx'],
          alias: {
              // Support React Native Web
              // https://www.smashingmagazine.com/2016/08/a-glimpse-into-the-future-with-react-native-for-web/
              'react-native': 'react-native-web',
          },
          plugins: [
              // Prevents users from importing files from outside of src/ (or node_modules/).
              // This often causes confusion because we only process files within src/ with babel.
              // To fix this, we prevent you from importing files out of src/ -- if you'd like to,
              // please link the files into your node_modules/ and let module-resolution kick in.
              // Make sure your source files are compiled, as they will not be processed in any way.
              new ModuleScopePlugin(paths.appSrc, [paths.appPackageJson]),
          ],
      },
      module: {
          strictExportPresence: true,
          rules: [
              // TODO: Disable require.ensure as it's not a standard language feature.
              // We are waiting for https://github.com/facebookincubator/create-react-app/issues/2176.
              // { parser: { requireEnsure: false } },
  
              // First, run the linter.
              // It's important to do this before Babel processes the JS.
              {
                  test: /\.(js|jsx|mjs)$/,
                  enforce: 'pre',
                  use: [
                      {
                          options: {
                              formatter: eslintFormatter,
                              eslintPath: require.resolve('eslint'),
                          },
                          loader: require.resolve('eslint-loader'),
                      },
                  ],
                  include: paths.appSrc,
              },
              {
                  // "oneOf" will traverse all following loaders until one will
                  // match the requirements. When no loader matches it will fall
                  // back to the "file" loader at the end of the loader list.
                  oneOf: [
                      // "url" loader works just like "file" loader but it also embeds
                      // assets smaller than specified size as data URLs to avoid requests.
                      {
                          test: [/\.bmp$/, /\.gif$/, /\.jpe?g$/, /\.png$/],
                          loader: require.resolve('url-loader'),
                          options: {
                              limit: 10000,
                              name: 'static/media/[name].[hash:8].[ext]',
                          },
                      },
                      // Process JS with Babel.
                      {
                          test: /\.(js|jsx|mjs)$/,
                          include: paths.appSrc,
                          loader: require.resolve('babel-loader'),
                          options: {
                              compact: true,
                          },
                      },
                      // The notation here is somewhat confusing.
                      // "postcss" loader applies autoprefixer to our CSS.
                      // "css" loader resolves paths in CSS and adds assets as dependencies.
                      // "style" loader normally turns CSS into JS modules injecting <style>,
                      // but unlike in development configuration, we do something different.
                      // `ExtractTextPlugin` first applies the "postcss" and "css" loaders
                      // (second argument), then grabs the result CSS and puts it into a
                      // separate file in our build process. This way we actually ship
                      // a single CSS file in production instead of JS code injecting <style>
                      // tags. If you use code splitting, however, any async bundles will still
                      // use the "style" loader inside the async code so CSS from them won't be
                      // in the main CSS file.
                      {
                          test: /\.css$/,
                          loader: ExtractTextPlugin.extract(
                              Object.assign(
                                  {
                                      fallback: {
                                          loader: require.resolve('style-loader'),
                                          options: {
                                              hmr: false,
                                          },
                                      },
                                      use: [
                                          {
                                              loader: require.resolve('css-loader'),
                                              options: {
                                                  importLoaders: 1,
                                                  minimize: true,
                                                  sourceMap: shouldUseSourceMap,
                                              },
                                          },
                                          {
                                              loader: require.resolve('postcss-loader'),
                                              options: {
                                                  // Necessary for external CSS imports to work
                                                  // https://github.com/facebookincubator/create-react-app/issues/2677
                                                  ident: 'postcss',
                                                  plugins: () => [
                                                      require('postcss-flexbugs-fixes'),
                                                      autoprefixer({
                                                          browsers: [
                                                              '>1%',
                                                              'last 4 versions',
                                                              'Firefox ESR',
                                                              'not ie < 9', // React doesn't support IE8 anyway
                                                          ],
                                                          flexbox: 'no-2009',
                                                      }),
                                                  ],
                                              },
                                          },
                                      ],
                                  },
                                  extractTextPluginOptions
                              )
                          ),
                          // Note: this won't work without `new ExtractTextPlugin()` in `plugins`.
                      },
                      // "file" loader makes sure assets end up in the `build` folder.
                      // When you `import` an asset, you get its filename.
                      // This loader doesn't use a "test" so it will catch all modules
                      // that fall through the other loaders.
                      {
                          loader: require.resolve('file-loader'),
                          // Exclude `js` files to keep "css" loader working as it injects
                          // it's runtime that would otherwise processed through "file" loader.
                          // Also exclude `html` and `json` extensions so they get processed
                          // by webpacks internal loaders.
                          exclude: [/\.js$/, /\.html$/, /\.json$/],
                          options: {
                              name: 'static/media/[name].[hash:8].[ext]',
                          },
                      },
                      // ** STOP ** Are you adding a new loader?
                      // Make sure to add the new loader(s) before the "file" loader.
                  ],
              },
          ],
      },
      plugins: [
          // Makes some environment variables available in index.html.
          // The public URL is available as %PUBLIC_URL% in index.html, e.g.:
          // <link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
          // In production, it will be an empty string unless you specify "homepage"
          // in `package.json`, in which case it will be the pathname of that URL.
          new InterpolateHtmlPlugin(env.raw),
          // Generates an `index.html` file with the <script> injected.
          new HtmlWebpackPlugin({
              inject: true,
              template: paths.appHtml,
              minify: {
                  removeComments: true,
                  collapseWhitespace: true,
                  removeRedundantAttributes: true,
                  useShortDoctype: true,
                  removeEmptyAttributes: true,
                  removeStyleLinkTypeAttributes: true,
                  keepClosingSlash: true,
                  minifyJS: true,
                  minifyCSS: true,
                  minifyURLs: true,
              },
          }),
          // Makes some environment variables available to the JS code, for example:
          // if (process.env.NODE_ENV === 'production') { ... }. See `./env.js`.
          // It is absolutely essential that NODE_ENV was set to production here.
          // Otherwise React will be compiled in the very slow development mode.
          new webpack.DefinePlugin(env.stringified),
          // Minify the code.
          new webpack.optimize.UglifyJsPlugin({
              compress: {
                  warnings: false,
                  // Disabled because of an issue with Uglify breaking seemingly valid code:
                  // https://github.com/facebookincubator/create-react-app/issues/2376
                  // Pending further investigation:
                  // https://github.com/mishoo/UglifyJS2/issues/2011
                  comparisons: false,
              },
              mangle: {
                  safari10: true,
              },
              output: {
                  comments: false,
                  // Turned on because emoji and regex is not minified properly using default
                  // https://github.com/facebookincubator/create-react-app/issues/2488
                  ascii_only: true,
              },
              sourceMap: shouldUseSourceMap,
          }),
          // Note: this won't work without ExtractTextPlugin.extract(..) in `loaders`.
          new ExtractTextPlugin({
              filename: cssFilename,
          }),
          // Generate a manifest file which contains a mapping of all asset filenames
          // to their corresponding output file so that tools can pick it up without
          // having to parse `index.html`.
          new ManifestPlugin({
              fileName: 'asset-manifest.json',
          }),
          // Generate a service worker script that will precache, and keep up to date,
          // the HTML & assets that are part of the Webpack build.
          new SWPrecacheWebpackPlugin({
              // By default, a cache-busting query parameter is appended to requests
              // used to populate the caches, to ensure the responses are fresh.
              // If a URL is already hashed by Webpack, then there is no concern
              // about it being stale, and the cache-busting can be skipped.
              dontCacheBustUrlsMatching: /\.\w{8}\./,
              filename: 'service-worker.js',
              logger(message) {
                  if (message.indexOf('Total precache size is') === 0) {
                      // This message occurs for every build and is a bit too noisy.
                      return;
                  }
                  if (message.indexOf('Skipping static resource') === 0) {
                      // This message obscures real errors so we ignore it.
                      // https://github.com/facebookincubator/create-react-app/issues/2612
                      return;
                  }
                  console.log(message);
              },
              minify: true,
              // For unknown URLs, fallback to the index page
              navigateFallback: publicUrl + '/index.html',
              // Ignores URLs starting from /__ (useful for Firebase):
              // https://github.com/facebookincubator/create-react-app/issues/2237#issuecomment-302693219
              navigateFallbackWhitelist: [/^(?!\/__).*/],
              // Don't precache sourcemaps (they're large) and build asset manifest:
              staticFileGlobsIgnorePatterns: [/\.map$/, /asset-manifest\.json$/],
          }),
          // Moment.js is an extremely popular library that bundles large locale files
          // by default due to how Webpack interprets its code. This is a practical
          // solution that requires the user to opt into importing specific locales.
          // https://github.com/jmblog/how-to-optimize-momentjs-with-webpack
          // You can remove this if you don't use Moment.js:
          new webpack.IgnorePlugin(/^\.\/locale$/, /moment$/),
      ],
      // Some libraries import Node modules but don't use them in the browser.
      // Tell Webpack to provide empty mocks for them so importing them works.
      node: {
          dgram: 'empty',
          fs: 'empty',
          net: 'empty',
          tls: 'empty',
          child_process: 'empty',
      },
  };
  