/** Pure: fetches WebRTC failure reason (e.g. wrong host). Returns frozen object. */
export async function getWebRTCFailureReason() {
  try {
    const res = await $fetch('/api/live/debug-request-host', { credentials: 'include' })
    const clientHostname = typeof window !== 'undefined' ? window.location.hostname : ''
    const serverHostname = res?.hostname ?? ''
    if (serverHostname && clientHostname && serverHostname !== clientHostname) {
      return Object.freeze({ wrongHost: Object.freeze({ serverHostname, clientHostname }) })
    }
  }
  catch { /* ignore */ }
  return Object.freeze({ wrongHost: null })
}