'use strict';

const path = require('path');
const webpack = require('webpack');
const ExtractTextPlugin = require('extract-text-webpack-plugin');
const ManifestPlugin = require('webpack-manifest-plugin');
const ResolveEntryModulesPlugin = require("resolve-entry-modules-webpack-plugin");
const atImport = require('postcss-import');
const postcssURL = require("postcss-url");
const cssNext = require('postcss-cssnext');
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.publicPath;
// 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 === './';
// Get environment variables to inject into our app.
const env = getClientEnvironment();

// 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.');
}

// Allow hashing to be disabled by passing an ENV
let hashFilenames = true;
if (
  env.stringified['process.env'].ASSETS_HASH_FILENAMES
  && env.stringified['process.env'].ASSETS_HASH_FILENAMES === '"false"'
) {
  hashFilenames = false;
}

// Note: defined here because it will be used more than once.
const cssFilename = hashFilenames ? '[name].[contenthash:8].css' : '[name].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',
  // Specify the context we expect app code to be loaded from
  context: paths.appSrc,
  // In production, we only want to load the polyfills and the app code.
  entry: paths.appEntries.reduce((output, entry) => {
    const [name, location] = entry
    output[name] = [
      // We ship a few polyfills by default
      require.resolve('./polyfills'),
      location,
    ]
    return output
  }, {}),
  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: hashFilenames ? '[name].[chunkhash:8].js' : '[name].js',
    chunkFilename: hashFilenames ? '[name].[chunkhash:8].chunk.js' : '[name].chunk.js',
    // We inferred the "public path" (such as / or /my-project) from homepage.
    publicPath: publicPath,
  },
  resolve: {
    // This allows you to set a fallback for where Webpack should look for modules.
    // We read `NODE_PATH` environment variable in `paths.js` and pass paths here.
    // 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']
      .concat(paths.nodePaths),
    // 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'],
  },
  // Resolve loaders (webpack plugins for CSS, images, transpilation) from the
  // directory of `icelab-assets` itself rather than the project directory.
  resolveLoader: {
    modules: [
      paths.ownNodeModules,
      paths.appNodeModules,
    ],
  },
  module: {
    rules: [
      // Disable require.ensure as it's not a standard language feature.
      { parser: { requireEnsure: false } },
      // First, run the linter.
      // It's important to do this before Babel processes the JS.
      {
        test: /\.(js|jsx)$/,
        enforce: 'pre',
        use: [
          {
            // Point ESLint to our predefined config.
            options: {
              // Separate config for production to enable no-debugger only in
              // production.
              configFile: path.join(__dirname, '../eslintrc.prod'),
              useEslintrc: false,
            },
            loader: 'eslint-loader',
          },
        ],
        include: paths.appSrc,
      },
      // ** ADDING/UPDATING LOADERS **
      // The "url" 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 "url" loader.

      // "file" loader makes sure those assets end up in the `build` folder.
      // When you `import` an asset, you get its filename.
      {
        exclude: [
          /\.html$/,
          /\.(js|jsx)$/,
          /\.css$/,
          /\.json$/
        ],
        use: [{
          loader: 'file-loader',
          options: {
            name: hashFilenames ? '[path][name].[hash:8].[ext]' : '[path][name].[ext]',
          },
        }],
      },
      // Process JS with Babel.
      {
        test: /\.(js|jsx)$/,
        include: paths.appSrc,
        use: [{
          loader: 'babel-loader',
          options: {
            babelrc: true,
            presets: [require.resolve('babel-preset-react-app')],
            plugins: [require.resolve('babel-plugin-syntax-dynamic-import')],
          },
        }],
      },
      // The notation here is somewhat confusing.
      // "postcss" loader applies autoprefixer to our CSS.
      // "css" loader resolves paths in CSS and adds assets as dependencies.
      // "style" loader normally turns CSS into JS modules injecting <style>,
      // but unlike in development configuration, we do something different.
      // `ExtractTextPlugin` first applies the "postcss" and "css" loaders
      // (second argument), then grabs the result CSS and puts it into a
      // separate file in our build process. This way we actually ship
      // a single CSS file in production instead of JS code injecting <style>
      // tags. If you use code splitting, however, any async bundles will still
      // use the "style" loader inside the async code so CSS from them won't be
      // in the main CSS file.
      {
        test: /\.css$/,
        use: ExtractTextPlugin.extract(
          Object.assign(
            {
              fallback: 'style-loader',
              use: [
                {
                  loader: 'css-loader',
                  options: {
                    importLoaders: 1,
                    minimize: true,
                  },
                },
                {
                  loader: 'postcss-loader',
                  options: {
                    ident: 'postcss', // https://webpack.js.org/guides/migrating/#complex-options
                    plugins: () => [
                      // Add module-like @import support to our CSS. This sets the context for all imports
                      // to be the base entry point.
                      atImport(),
                      // postcss-url "rebases" any `url()` references in CSS to their original relative
                      // position on the filesystem (so that postcss-import doesn't break things)
                      postcssURL(),
                      // cssnext gives us compilation of future-CSS syntax, it also includes autoprefixer
                      // so we don't need to add that separately.
                      cssNext({
                        browsers: [
                          '>1%',
                          'last 4 versions',
                          'Firefox ESR',
                          'not ie < 9', // React doesn't support IE8 anyway
                        ],
                        features: {
                          customProperties: {
                            warnings: false
                          }
                        },
                      }),
                    ],
                  },
                },
              ],
            },
            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 "url" loader exclusion list.
    ],
  },
  plugins: [
    // 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),
    // Expose each entry as a resolution point so that we can resolve from the
    // root of each entry point and avoid relative requires
    new ResolveEntryModulesPlugin(),
    // Minify the code.
    new webpack.optimize.UglifyJsPlugin({
      compress: {
        screw_ie8: true, // React doesn't support IE8
        warnings: false,
      },
      mangle: {
        screw_ie8: true,
      },
      output: {
        comments: false,
        screw_ie8: true,
      },
      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',
    }),
  ],
  // 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',
  },
};