package checker

import "net"

// starttlsUpgrader performs the plaintext portion of a STARTTLS upgrade on
// conn, leaving conn ready for tls.Client(conn, …).Handshake(). On success
// the returned function returns nil; on failure it returns a descriptive
// error (wrap errStartTLSNotOffered when the server advertises no STARTTLS).
type starttlsUpgrader func(conn net.Conn, sni string) error

var starttlsUpgraders = map[string]starttlsUpgrader{}

func registerStartTLS(protocol string, upgrader starttlsUpgrader) {
	starttlsUpgraders[protocol] = upgrader
}