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 === './';
  // `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: 'source-map',
    // 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
      devtoolModuleFilenameTemplate: info =>
        path.relative(paths.appSrc, info.absoluteResourcePath),
    },
    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
      extensions: ['.js', '.json', '.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),
      ],
    },
    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)$/,
          enforce: 'pre',
          use: [
            {
              options: {
                formatter: eslintFormatter,
  
              },
              loader: require.resolve('eslint-loader'),
            },
          ],
          include: paths.appSrc,
        },
        // ** ADDING/UPDATING LOADERS **
        // The "file" loader handles all assets unless explicitly excluded.
        // The `exclude` list *must* be updated with every change to loader extensions.
        // When adding a new loader, you must add its `test`
        // as a new entry in the `exclude` list in the "file" loader.
  
        // "file" loader makes sure those assets end up in the `build` folder.
        // When you `import` an asset, you get its filename.
        {
          exclude: [
            /\.html$/,
            /\.pug$/,
            /\.(js|jsx)$/,
            /\.css$/,
            /\.json$/,
            /\.bmp$/,
            /\.gif$/,
            /\.jpe?g$/,
            /\.png$/,
          ],
          loader: require.resolve('file-loader'),
          options: {
            name: 'static/media/[name].[hash:8].[ext]',
          },
        },
        // "url" loader works just like "file" loader but it also embeds
        // assets smaller than specified size as data URLs to avoid requests.
        {
          test: [/\.bmp$/, /\.gif$/, /\.jpe?g$/, /\.png$/],
          loader: require.resolve('url-loader'),
          options: {
            limit: 10000,
            name: 'static/media/[name].[hash:8].[ext]',
          },
        },
        // Process pug as jsx.
        {
          test: /\.pug$/,
          include: paths.appSrc,
          use: [
            require.resolve('babel-loader'),
            require.resolve('pug-as-jsx-loader'),
          ],
        },
        // Process JS with Babel.
        {
          test: /\.(js|jsx)$/,
          include: paths.appSrc,
          loader: require.resolve('babel-loader'),
  
        },
        // 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: require.resolve('style-loader'),
                use: [
                  {
                    loader: require.resolve('css-loader'),
                    options: {
                      importLoaders: 1,
                      minimize: true,
                      sourceMap: true,
                    },
                  },
                  {
                    loader: require.resolve('postcss-loader'),
                    options: {
                      ident: 'postcss', // https://webpack.js.org/guides/migrating/#complex-options
                      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`.
        },
        // ** STOP ** Are you adding a new loader?
        // Remember to add the new extension(s) to the "file" loader exclusion list.
      ],
    },
    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,
        },
        output: {
          comments: false,
        },
        sourceMap: true,
      }),
      // 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;
          }
          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$/],
        // Work around Windows path issue in SWPrecacheWebpackPlugin:
        // https://github.com/facebookincubator/create-react-app/issues/2235
        stripPrefix: paths.appBuild.replace(/\\/g, '/') + '/',
      }),
      // Moment.js is an extremely popular library that bundles large locale files
      // by default due to how Webpack interprets its code. This is a practical
      // solution that requires the user to opt into importing specific locales.
      // https://github.com/jmblog/how-to-optimize-momentjs-with-webpack
      // You can remove this if you don't use Moment.js:
      new webpack.IgnorePlugin(/^\.\/locale$/, /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: {
      fs: 'empty',
      net: 'empty',
      tls: 'empty',
    },
  };
  