export interface ParsedFqdn {
  zoneName: string
  hostname: string
  fqdn: string
}

export function fqdnToDisplay(hostname: string, zoneName: string): string {
  if (hostname === '@') {
    return zoneName
  }
  return `${hostname}.${zoneName}`
}

export function parseFqdn(fqdn: string, knownZones: string[]): ParsedFqdn | null {
  const normalized = fqdn.trim().toLowerCase()
  if (!normalized) {
    return null
  }

  const zones = [...knownZones].sort((a, b) => b.length - a.length)

  for (const zone of zones) {
    const zoneLower = zone.toLowerCase()
    if (normalized === zoneLower) {
      return {
        zoneName: zone,
        hostname: '@',
        fqdn: fqdnToDisplay('@', zone),
      }
    }
    const suffix = `.${zoneLower}`
    if (normalized.endsWith(suffix)) {
      const prefix = normalized.slice(0, -suffix.length)
      if (prefix) {
        return {
          zoneName: zone,
          hostname: prefix,
          fqdn: fqdnToDisplay(prefix, zone),
        }
      }
    }
  }

  return null
}

export function bindingToFqdn(binding: {
  hostname: string
  zone_name: string
  fqdn?: string
}): string {
  return binding.fqdn ?? fqdnToDisplay(binding.hostname, binding.zone_name)
}