package resolver

import (
	"errors"
	"testing"
	"time"

	"github.com/miekg/dns"
)

// TestAnswerForAnotherQuestionIsRejected pins the check the DNS library does
// not make: it matches the message ID and nothing else, so a reply with the
// right ID for a different question would otherwise be cached under the name
// that was asked.
func TestAnswerForAnotherQuestionIsRejected(t *testing.T) {
	spoof := newFakeUpstream(t, fakeOpt{wrongQuestion: true})
	p := NewPool(poolCfg(udpServer(spoof.addr)))
	for i := 0; i < 5; i++ { // more than the breaker threshold
		resp, _, err := p.Exchange(testCtx(t), query("www.example.test"), nil, time.Second)
		if !errors.Is(err, errQuestionMismatch) || resp != nil {
			t.Fatalf("attempt %d: resp=%v err=%v, want the mismatch error", i, resp, err)
		}
	}
	// A forged reply must not be able to take the upstream out of rotation.
	if up := p.All()[0]; up.BreakerOpen() {
		t.Fatal("spoofed replies opened the circuit breaker")
	}
}

func TestAnswersQuestion(t *testing.T) {
	q := query("WWW.Example.Test")
	reply := func(name string, qtype uint16, rcode int, drop bool) *dns.Msg {
		m := new(dns.Msg)
		m.SetReply(q)
		m.Question[0].Name, m.Question[0].Qtype = name, qtype
		m.Rcode = rcode
		if drop {
			m.Question = nil
		}
		return m
	}
	for name, tc := range map[string]struct {
		resp *dns.Msg
		want bool
	}{
		"same":                  {reply("www.example.test.", dns.TypeA, 0, false), true},
		"case differs":          {reply("WWW.EXAMPLE.TEST.", dns.TypeA, 0, false), true},
		"other name":            {reply("evil.example.", dns.TypeA, 0, false), false},
		"other type":            {reply("www.example.test.", dns.TypeAAAA, 0, false), false},
		"formerr, no question":  {reply("", 0, dns.RcodeFormatError, true), true},
		"refused, no question":  {reply("", 0, dns.RcodeRefused, true), true},
		"success, no question":  {reply("", 0, dns.RcodeSuccess, true), false},
		"nxdomain, no question": {reply("", 0, dns.RcodeNameError, true), false},
		"nil":                   {nil, false},
	} {
		if got := answersQuestion(q, tc.resp); got != tc.want {
			t.Errorf("%s: got %v, want %v", name, got, tc.want)
		}
	}
}