next.config.js

const isProduction = process.env.NODE_ENV === 'production';
require('dotenv').config({
  path: isProduction ? `.env.${process.env.ENV}` : '.env',
});

const withImages = require('next-images');
const withOffline = require('next-offline');

const LodashModuleReplacementPlugin = require('lodash-webpack-plugin');

const regexEqual = (x, y) => {
  return (
    x instanceof RegExp &&
    y instanceof RegExp &&
    x.source === y.source &&
    x.global === y.global &&
    x.ignoreCase === y.ignoreCase &&
    x.multiline === y.multiline
  );
};

const withPolyfills = (module.exports = (nextConfig = {}) => {
  return Object.assign({}, nextConfig, {
    webpack(config, options) {
      const originalEntry = config.entry;
      config.entry = function entry() {
        return Promise.resolve(originalEntry()).then((entries) => {
          if (entries['main.js']) {
            entries['main.js'].unshift('./polyfills.js');
          }

          return entries;
        });
      };

      const oneOf = config.module.rules.find((rule) => typeof rule.oneOf === 'object');

      if (oneOf) {
        const moduleSassRule = oneOf.oneOf.find((rule) =>
          regexEqual(rule.test, /\.module\.(scss|sass)$/)
        );

        if (moduleSassRule) {
          const cssLoader = moduleSassRule.use.find(({ loader }) => loader.includes('css-loader'));
          if (cssLoader) {
            cssLoader.options.localsConvention = 'camelCase';
          }
        }
      }

      if (typeof nextConfig.webpack === 'function') {
        return nextConfig.webpack(config, options);
      }

      return config;
    },
  });
});

const config = withPolyfills(
  withImages({
    webpack: (config, options) => {
      config.plugins.push(new LodashModuleReplacementPlugin());
      return config;
    },
  })
);

config.exportPathMap = function () {
  return {
    '/about': { page: '/about' },
    '/authors': { page: '/authors' },
    '/regulations': { page: '/regulations' },
  };
};

config.experimental = {
  publicDirectory: true,
};

config.env = {
  API_URL: process.env.API_URL,
  VERSION: process.env.VERSION,
  GA_TRACKING_ID: process.env.GA_TRACKING_ID,
  ABSOLUTE_URL: process.env.ABSOLUTE_URL || 'https://' + process.env.VERCEL_URL,
  SENTRY_DSN: process.env.SENTRY_DSN,
  ENV: process.env.ENV,
};

const path = require('path');
config.sassOptions = {
  includePaths: [path.join(__dirname, 'styles')],
};

module.exports = isProduction ? withOffline(config) : config;