const BundleAnalyzerPlugin = require('webpack-bundle-analyzer').BundleAnalyzerPlugin;
const autoprefixer = require('autoprefixer');
const cssvars = require('postcss-simple-vars');
const webpack = require('webpack');

const UglifyJSPlugin = require('uglifyjs-webpack-plugin')
const HtmlWebpackPlugin = require('html-webpack-plugin');
const ExtractTextPlugin = require('extract-text-webpack-plugin');
const ManifestPlugin = require('webpack-manifest-plugin');
const url = require('url');

var paths = require('./paths');
var getClientEnvironment = require('./env');

var cssvariables = require(paths.appSrc + '/theme/variables');

const postcssPlugins = [
  autoprefixer({
    browsers: [
      '>1%',
      'last 4 versions',
      'Firefox ESR',
      'not ie < 9', // React doesn't support IE8 anyway
    ]
  }),
  cssvars({
    variables: function () {
        return Object.assign({}, cssvariables);
    },
    silent: true
  }),
];

function ensureSlash(path, needsSlash) {
  var hasSlash = path.endsWith('/');
  if (hasSlash && !needsSlash) {
    return path.substr(path, path.length - 1);
  } else if (!hasSlash && needsSlash) {
    return path + '/';
  } else {
    return path;
  }
}

// We use "homepage" field to infer "public path" at which the app is served.
// Webpack needs to know it to put the right <script> hrefs into HTML even in
// single-page apps that may serve index.html for nested URLs like /todos/42.
// We can't use a relative path in HTML because we don't want to load something
// like /todos/42/static/js/bundle.7289d.js. We have to know the root.
var homepagePath = require(paths.appPackageJson).homepage;
var homepagePathname = homepagePath ? url.parse(homepagePath).pathname : '/';
// 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.
var publicPath = ensureSlash(homepagePathname, true);
// `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_PATH%/xyz looks better than %PUBLIC_PATH%xyz.
var publicUrl = ensureSlash(homepagePathname, false);
// Get environment variables to inject into our app.
var env = getClientEnvironment(publicUrl);

// Assert this just to be safe.
// Development builds of React are slow and not intended for production.
if (env['process.env'].NODE_ENV !== '"production"') {
  throw new Error('Production builds must have NODE_ENV=production.');
}

// 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 = {
  mode: 'production',
  // Don't attempt to continue if there are any errors.
  bail: true,
  optimization: {
    splitChunks: {
      cacheGroups: {
        vendor: {
          test: /node_modules/,
          name: "vendor",
          chunks: "all",
          enforce: true,
          minSize: 1
        }
      }
    }
  },
  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
  },
  resolve: {
    // 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'],
  },

  module: {
    rules: [
      {
        test: /\.(js|jsx)$/,
        include: paths.appSrc,
        use: {
          loader: "babel-loader"
        }
      },
      {
        test: /\.(scss|css)$/,
        use: ExtractTextPlugin.extract({
          fallback: 'style-loader',
          use: [
            { 
              loader: 'css-loader',
              options: {
                importLoaders: 1,
                modules: true,
                minimize: true
              }
            },
            {
              loader: 'postcss-loader',
              options: {
                sourceMap: true,
                plugins: postcssPlugins,
              }
            },
          ],
        })
      },
    ]
  },
  plugins: [
    // 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),
    // Note: this won't work without ExtractTextPlugin.extract(..) in `loaders`.
    new ExtractTextPlugin('static/css/[name].[contenthash:8].css'),
    // 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'
    }),
    // new BundleAnalyzerPlugin()
  ],
  // 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'
  }
};