'use strict';
 
 const errorOverlayMiddleware = require('react-dev-utils/errorOverlayMiddleware');
 const noopServiceWorkerMiddleware = require('react-dev-utils/noopServiceWorkerMiddleware');
 const ignoredFiles = require('react-dev-utils/ignoredFiles');
 const config = require('./webpack.config.dev');
 const paths = require('./paths');
 
 const protocol = process.env.HTTPS === 'true' ? 'https' : 'http';
 const host = process.env.HOST || '0.0.0.0';
 
 module.exports = function(proxy, allowedHost) {
   return {
     // WebpackDevServer 2.4.3 introduced a security fix that prevents remote
     // websites from potentially accessing local content through DNS rebinding:
     // https://github.com/webpack/webpack-dev-server/issues/887
     // https://medium.com/webpack/webpack-dev-server-middleware-security-issues-1489d950874a
     // However, it made several existing use cases such as development in cloud
     // environment or subdomains in development significantly more complicated:
     // https://github.com/facebookincubator/create-react-app/issues/2271
     // https://github.com/facebookincubator/create-react-app/issues/2233
     // While we're investigating better solutions, for now we will take a
     // compromise. Since our WDS configuration only serves files in the `public`
     // folder we won't consider accessing them a vulnerability. However, if you
     // use the `proxy` feature, it gets more dangerous because it can expose
     // remote code execution vulnerabilities in backends like Django and Rails.
     // So we will disable the host check normally, but enable it if you have
     // specified the `proxy` setting. Finally, we let you override it if you
     // really know what you're doing with a special environment variable.
     disableHostCheck:
       !proxy || process.env.DANGEROUSLY_DISABLE_HOST_CHECK === 'true',
     // Enable gzip compression of generated files.
     compress: true,
     // Silence WebpackDevServer's own logs since they're generally not useful.
     // It will still show compile warnings and errors with this setting.
     clientLogLevel: 'none',
     // By default WebpackDevServer serves physical files from current directory
     // in addition to all the virtual build products that it serves from memory.
     // This is confusing because those files won’t automatically be available in
     // production build folder unless we copy them. However, copying the whole
     // project directory is dangerous because we may expose sensitive files.
     // Instead, we establish a convention that only files in `public` directory
     // get served. Our build script will copy `public` into the `build` folder.
     // In `index.html`, you can get URL of `public` folder with %PUBLIC_URL%:
     // <link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
     // In JavaScript code, you can access it with `process.env.PUBLIC_URL`.
     // Note that we only recommend to use `public` folder as an escape hatch
     // for files like `favicon.ico`, `manifest.json`, and libraries that are
     // for some reason broken when imported through Webpack. If you just want to
     // use an image, put it in `src` and `import` it from JavaScript instead.
     contentBase: paths.appPublic,
     // By default files from `contentBase` will not trigger a page reload.
     watchContentBase: true,
     // Enable hot reloading server. It will provide /sockjs-node/ endpoint
     // for the WebpackDevServer client so it can learn when the files were
     // updated. The WebpackDevServer client is included as an entry point
     // in the Webpack development configuration. Note that only changes
     // to CSS are currently hot reloaded. JS changes will refresh the browser.
     hot: true,
     // It is important to tell WebpackDevServer to use the same "root" path
     // as we specified in the config. In development, we always serve from /.
     publicPath: config.output.publicPath,
     // WebpackDevServer is noisy by default so we emit custom message instead
     // by listening to the compiler events with `compiler.plugin` calls above.
     quiet: true,
     // Reportedly, this avoids CPU overload on some systems.
     // https://github.com/facebookincubator/create-react-app/issues/293
     // src/node_modules is not ignored to support absolute imports
     // https://github.com/facebookincubator/create-react-app/issues/1065
     watchOptions: {
       ignored: ignoredFiles(paths.appSrc),
     },
     // Enable HTTPS if the HTTPS environment variable is set to 'true'
     https: protocol === 'https',
     host: host,
     overlay: false,
     historyApiFallback: {
       // Paths with dots should still use the history fallback.
       // See https://github.com/facebookincubator/create-react-app/issues/387.
       disableDotRule: true,
     },
     public: allowedHost,
     proxy,
     before(app) {
       // This lets us open files from the runtime error overlay.
       app.use(errorOverlayMiddleware());
       // This service worker file is effectively a 'no-op' that will reset any
       // previous service worker registered for the same host:port combination.
       // We do this in development to avoid hitting the production cache if
       // it used the same host and port.
       // https://github.com/facebookincubator/create-react-app/issues/2272#issuecomment-302832432
       app.use(noopServiceWorkerMiddleware());
     },
   };
 };