package xmpp

import (
	"fmt"
	"net"
)

const (
	// Standard port for XMPP clients to connect to.
	XMPP_CLIENT_PORT = 5222
)

// Perform a DNS SRV lookup and return an ordered list of "host:port" TCP
// addresses for the JID's home server. If no SRV records are found then assume
// the JID's domain is also the home server.
func HomeServerAddrs(jid JID) (addr []string, err error) {

	// DNS lookup.
	_, addrs, _ := net.LookupSRV("xmpp-client", "tcp", jid.Domain)

	// If there's nothing in DNS then assume the JID's domain and the standard
	// port will work.
	if len(addrs) == 0 {
		addr = []string{fmt.Sprintf("%s:%d", jid.Domain, XMPP_CLIENT_PORT)}
		return
	}

	// Build list of "host:port" strings.
	for _, a := range addrs {
		target := parseTargetDomainName(a.Target)
		addr = append(addr, fmt.Sprintf("%s:%d", target, a.Port))
	}
	return
}

// Remove the last dot in the domain name if exist
func parseTargetDomainName(domainName string) (ret string) {
	if domainName[len(domainName)-1] == '.' {
		ret = parseTargetDomainName(domainName[:len(domainName)-1])
	} else {
		ret = domainName
	}
	return
}