package httpx

import (
	"net"
	"strings"
)

// IsLoopbackHost reports whether a request Host ("host" or "host:port") names a
// loopback origin.
//
// It gates the passkey nudge (SPEC-006 §8): a passkey registered at
// `127.0.0.1` binds the Relying Party ID `127.0.0.1` and is UNUSABLE at the
// public domain (O-13/D-041), so the nudge is suppressed on loopback. An
// empty/unknown host is treated as loopback — fail closed, so an origin we
// cannot classify never triggers the nudge.
func IsLoopbackHost(hostport string) bool {
	host := strings.TrimSpace(hostport)
	if h, _, err := net.SplitHostPort(host); err == nil {
		host = h
	}
	host = strings.Trim(strings.TrimSpace(host), "[]")
	if host == "" {
		return true
	}
	if strings.EqualFold(host, "localhost") {
		return true
	}
	ip := net.ParseIP(host)
	return ip != nil && ip.IsLoopback()
}