package resolver

import (
	"context"
	"time"

	"github.com/miekg/dns"
)

// DNSClient abstracts DNS wire-protocol exchanges so the resolver
// can be tested without hitting real nameservers.
type DNSClient interface {
	ExchangeContext(
		ctx context.Context,
		msg *dns.Msg,
		addr string,
	) (*dns.Msg, time.Duration, error)
}

// udpClient wraps a real dns.Client for production use.
type udpClient struct {
	timeout time.Duration
}

func (c *udpClient) ExchangeContext(
	ctx context.Context,
	msg *dns.Msg,
	addr string,
) (*dns.Msg, time.Duration, error) {
	cl := &dns.Client{Timeout: c.timeout}

	return cl.ExchangeContext(ctx, msg, addr)
}

// tcpClient wraps a real dns.Client using TCP.
type tcpClient struct {
	timeout time.Duration
}

func (c *tcpClient) ExchangeContext(
	ctx context.Context,
	msg *dns.Msg,
	addr string,
) (*dns.Msg, time.Duration, error) {
	cl := &dns.Client{Net: "tcp", Timeout: c.timeout}

	return cl.ExchangeContext(ctx, msg, addr)
}