const path = require('path')

module.exports = (pluginOptions = {
  extension: /\.mdx?$/
}) => (nextConfig = {
  pageExtensions: ['js', 'jsx', 'md', 'mdx']
}) => {
  const extension = pluginOptions.extension || /\.mdx$/

  return Object.assign({}, nextConfig, {
    webpack(config, options) {
      config.module.rules.push({
        test: extension,
        use: [
          options.defaultLoaders.babel,
          {
            loader: '@mdx-js/loader',
            options: pluginOptions.options
          },
          {
            loader: path.resolve('.nextra', 'nextra-loader.js')
          }
        ]
      })

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

      return config
    }
  })
}