package updater

import (
	"context"
	"net"
)

func newResolver(resolverAddress string) *net.Resolver {
	return &net.Resolver{
		PreferGo: true,
		Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
			d := net.Dialer{}
			return d.DialContext(ctx, "udp", net.JoinHostPort(resolverAddress, "53"))
		},
	}
}

func newLookupIP(r *net.Resolver) lookupIPFunc {
	return func(ctx context.Context, host string) (ips []net.IP, err error) {
		addresses, err := r.LookupIPAddr(ctx, host)
		if err != nil {
			return nil, err
		}
		ips = make([]net.IP, len(addresses))
		for i := range addresses {
			ips[i] = addresses[i].IP
		}
		return ips, nil
	}
}

func resolveRepeat(ctx context.Context, lookupIP lookupIPFunc, host string, n int) (ips []net.IP, err error) {
	for i := 0; i < n; i++ {
		newIPs, err := lookupIP(ctx, host)
		if err != nil {
			return nil, err
		}
		ips = append(ips, newIPs...)
	}
	return uniqueSortedIPs(ips), nil
}