package dnsserver

import (
	"strings"

	"github.com/coredns/coredns/middleware"

	"github.com/miekg/dns"
)

type zoneAddr struct {
	Zone      string
	Port      string
	Transport string // dns, tls or grpc
}

// String return the string representation of z.
func (z zoneAddr) String() string { return z.Transport + "://" + z.Zone + ":" + z.Port }

// Transport returns the protocol of the string s
func Transport(s string) string {
	switch {
	case strings.HasPrefix(s, TransportTLS+"://"):
		return TransportTLS
	case strings.HasPrefix(s, TransportDNS+"://"):
		return TransportDNS
	case strings.HasPrefix(s, TransportGRPC+"://"):
		return TransportGRPC
	}
	return TransportDNS
}

// normalizeZone parses an zone string into a structured format with separate
// host, and port portions, as well as the original input string.
func normalizeZone(str string) (zoneAddr, error) {
	var err error

	// Default to DNS if there isn't a transport protocol prefix.
	trans := TransportDNS

	switch {
	case strings.HasPrefix(str, TransportTLS+"://"):
		trans = TransportTLS
		str = str[len(TransportTLS+"://"):]
	case strings.HasPrefix(str, TransportDNS+"://"):
		trans = TransportDNS
		str = str[len(TransportDNS+"://"):]
	case strings.HasPrefix(str, TransportGRPC+"://"):
		trans = TransportGRPC
		str = str[len(TransportGRPC+"://"):]
	}

	host, port, err := middleware.SplitHostPort(str)
	if err != nil {
		return zoneAddr{}, err
	}

	if port == "" {
		if trans == TransportDNS {
			port = Port
		}
		if trans == TransportTLS {
			port = TLSPort
		}
		if trans == TransportGRPC {
			port = GRPCPort
		}
	}

	return zoneAddr{Zone: dns.Fqdn(host), Port: port, Transport: trans}, nil
}

// Supported transports.
const (
	TransportDNS  = "dns"
	TransportTLS  = "tls"
	TransportGRPC = "grpc"
)