module.ts

import {
  defineNuxtModule,
  addServerHandler,
  createResolver,
  extendViteConfig,
  addServerPlugin,
} from '@nuxt/kit'
import { withQuery } from 'ufo'
import polyfillist from 'polyfillist'
import browserslistToEsbuild from 'browserslist-to-esbuild'

type AnyString = (string & Record<never, never>)

// Module options TypeScript interface definition
export interface ModuleOptions {
  target?: string | string[],
  host?: 'selfhost' | AnyString,
}

export default defineNuxtModule<ModuleOptions>({
  meta: {
    name     : 'nupolyon',
    configKey: 'nupolyon',
  },
  // Default configuration options of the Nuxt module
  defaults: {
    host: 'https://polyfill.io/v3/polyfill.min.js',
  },
  async setup (options, nuxt) {
    const resolver = createResolver(import.meta.url)

    const features   = await polyfillist(options.target)
    const isSelfHost = options.host === 'selfhost'
    const src        = options.host && !isSelfHost
      ? withQuery(options.host, { features: features.join(',') })
      : '/_nupolyon/polyfill'  // NOTE: app.baseUrl will be prepended to this path at runtime in the plugin.

    nuxt.options.runtimeConfig.nupolyon        = { features }
    nuxt.options.runtimeConfig.public.nupolyon = { src, isSelfHost }

    addServerPlugin(resolver.resolve('./runtime/server/plugins/polyfill'))

    if (isSelfHost) {
      addServerHandler({
        method : 'get',
        route  : '/_nupolyon/polyfill',
        handler: resolver.resolve('./runtime/selfhost')
      })
    }

    extendViteConfig((config) => {
      if (config.build)
        config.build.target = browserslistToEsbuild(options.target)
    })
  }
})