rsnext/packages/next/shared/lib/i18n/detect-domain-locale.ts

import type { DomainLocale } from '../../../server/config-shared'

export function detectDomainLocale(
  domainItems?: DomainLocale[],
  hostname?: string,
  detectedLocale?: string
) {
  let domainItem: DomainLocale | undefined

  if (domainItems) {
    if (detectedLocale) {
      detectedLocale = detectedLocale.toLowerCase()
    }

    for (const item of domainItems) {
      // remove port if present
      const domainHostname = item.domain?.split(':')[0].toLowerCase()
      if (
        hostname === domainHostname ||
        detectedLocale === item.defaultLocale.toLowerCase() ||
        item.locales?.some((locale) => locale.toLowerCase() === detectedLocale)
      ) {
        domainItem = item
        break
      }
    }
  }

  return domainItem
}