locale.config.js

const createI18nConfig = () => {
  const config = /** @type {const} */ ({
    locales: ['se', 'en'],
    localeLabel: {
      se: 'Svenska',
      en: 'English',
    },
    stripBase: true,
    base: 'se',
  })

  if (!config.locales.includes(config.base)) throw new Error(`Invalid base locale`)
  if (!config.locales.every((l) => !!config.localeLabel[l])) throw new Error(`Invalid localeLabel`)

  /** @type {{ [K in typeof config.locales[number]]: K }} */
  const LOCALE = config.locales.reduce((p, c) => {
    p[c] = c
    return p
  }, {})

  /** @type {{ id: typeof config.locales[number], title: typeof config.localeLabel[typeof config.locales[number]] }[]} */
  const languages = Object.entries(config.localeLabel).map(([k, v]) => ({id: k, title: v}))

  return {
    ...config,
    languages,
    LOCALE,
  }
}

const i18nConfig = createI18nConfig()

const localizeRoutes = (routeNamingLocale, routesManifest, translations) => {
  const otherLocales = i18nConfig.locales.filter((l) => l !== routeNamingLocale)

  const localizedRoutes = Object.fromEntries(
    Object.values(routesManifest).flatMap((v) => {
      if (!v.path) return [[v.id, v]]

      return translations.flatMap((t) => {
        if (v.file.startsWith(t.matchAll.replace('{{slug}}', t.slugs[routeNamingLocale]))) {
          return otherLocales.map((l) => [
            v.id,
            {
              ...v,
              path: v.path.replace(t.slugs[routeNamingLocale], t.slugs[l]),
              id: v.id.replace(t.slugs[routeNamingLocale], t.slugs[l]),
            },
          ])
        }
        return [[v.id, v]]
      })
    })
  )
  return localizedRoutes
}

module.exports = {i18nConfig, localizeRoutes}