const { merge } = require('webpack-merge')
const common = require('./webpack.common')

const MiniCssExtractPlugin = require('mini-css-extract-plugin')
const TerserPlugin = require('terser-webpack-plugin')
const CssMinimizerPlugin = require('css-minimizer-webpack-plugin')

module.exports = merge(common, {
  mode: 'production',
  output: {
    fileName: 'static/js/[name].[contenthash:8].js',
    chunkFilename: 'static/js/[name].[contenthash:8].chunk.js',
  },
  optimization: {
    minimize: true,
    minimizer: [
      new TerserPlugin({
        terserOptions: {
          parse: {
            // We want terser to parse ecma 8 code. However, we don't want it
            // to apply any minification steps that turns valid ecma 5 code
            // into invalid ecma 5 code. This is why the 'compress' and 'output'
            // sections only apply transformations that are ecma 5 safe
            // https://github.com/facebook/create-react-app/pull/4234
            ecma: 8,
          },
          compress: {
            ecma: 5,
            warnings: false,
            // Disabled because of an issue with Uglify breaking seemingly valid code:
            // https://github.com/facebook/create-react-app/issues/2376
            // Pending further investigation:
            // https://github.com/mishoo/UglifyJS2/issues/2011
            comparisons: false,
            // Disabled because of an issue with Terser breaking valid code:
            // https://github.com/facebook/create-react-app/issues/5250
            // Pending further investigation:
            // https://github.com/terser-js/terser/issues/120
            inline: 2,
          },
          mangle: {
            safari10: true,
          },
          // Added for profiling in devtools
          keep_classnames: false,
          keep_fnames: false,
          output: {
            ecma: 5,
            comments: false,
            // Turned on because emoji and regex is not minified properly using default
            // https://github.com/facebook/create-react-app/issues/2488
            ascii_only: true,
          },
        },
      }),
      new CssMinimizerPlugin(),
    ],
  },
  plugins: [
    new MiniCssExtractPlugin({
      filename: 'static/css/[name].[contenthash:8].css',
      chunkFilename: 'static/css/[name].[contenthash:8].chunk.css',
    }),
  ],
})