package dns

import (
	"fmt"
	"net"
)

// EnsureIPv4 ensures that an ipv4 address is set for a domain name
func EnsureIPv4(domainName string) (string, error) {
	ipv4, err := net.ResolveIPAddr("ip4", domainName)
	if err != nil {
		return "", err
	}

	// NOTE(d1): e.g. when there is only an ipv6 record available
	if ipv4 == nil {
		return "", fmt.Errorf("unable to resolve ipv4 address for %s", domainName)
	}

	return ipv4.String(), nil
}

// EnsureDomainsResolveSameIPv4 ensures that domains resolve to the same ipv4 address
func EnsureDomainsResolveSameIPv4(domainName, server string) (string, error) {
	if server == "default" || server == "local" {
		return "", nil
	}

	var ipv4 string

	domainIPv4, err := EnsureIPv4(domainName)
	if err != nil {
		return ipv4, err
	}

	if domainIPv4 == "" {
		return ipv4, fmt.Errorf("cannot resolve ipv4 for %s?", domainName)
	}

	serverIPv4, err := EnsureIPv4(server)
	if err != nil {
		return ipv4, err
	}

	if serverIPv4 == "" {
		return ipv4, fmt.Errorf("cannot resolve ipv4 for %s?", server)
	}

	if domainIPv4 != serverIPv4 {
		err := "app domain %s (%s) does not appear to resolve to app server %s (%s)?"
		return ipv4, fmt.Errorf(err, domainName, domainIPv4, server, serverIPv4)
	}

	return ipv4, nil
}