package traverse

import (
	"testing"

	"github.com/miekg/dns"
)

// rootedCache returns a cache seeded with root hints, as the traverser will
// always provide.
func rootedCache() *InfoCache {
	c := NewInfoCache(nil)
	c.AddHints("", []StartServer{{Name: "a.root-servers.net", IPs: []string{"198.41.0.4"}}})
	return c
}

func TestServerResponseReferralNotLame(t *testing.T) {
	// Root server refers com query to the gtld servers: "" → "com" is deeper.
	msg := newMsg("www.example.com", dns.TypeA, dns.RcodeSuccess)
	msg.Ns = append(msg.Ns, nsRR("com", "a.gtld-servers.net"))
	msg.Extra = append(msg.Extra, aRR("a.gtld-servers.net", "192.5.6.30"))
	dq := decode(msg, "www.example.com", dns.TypeA, "")

	r, err := NewServerResponse(dq, "a.root-servers.net", "", rootedCache())
	if err != nil {
		t.Fatalf("NewServerResponse: %v", err)
	}
	if r.Status != StatusReferral {
		t.Fatalf("status = %s, want referral", r.Status)
	}
	if r.StartersBailiwick != "com" {
		t.Errorf("starters bailiwick = %q, want com", r.StartersBailiwick)
	}
	if len(r.Starters) != 1 || r.Starters[0].Name != "a.gtld-servers.net" {
		t.Errorf("starters = %v", r.Starters)
	}
	if len(r.Starters[0].IPs) != 1 || r.Starters[0].IPs[0] != "192.5.6.30" {
		t.Errorf("starter IPs = %v", r.Starters[0].IPs)
	}
	if len(dq.Warnings) != 0 {
		t.Errorf("unexpected warnings: %v", dq.Warnings)
	}
}

func TestServerResponseGluelessStarterHasNilIPs(t *testing.T) {
	msg := newMsg("www.example.com", dns.TypeA, dns.RcodeSuccess)
	msg.Ns = append(msg.Ns, nsRR("example.com", "ns1.example.com"))
	dq := decode(msg, "www.example.com", dns.TypeA, "com")

	r, err := NewServerResponse(dq, "a.gtld-servers.net", "", rootedCache())
	if err != nil {
		t.Fatalf("NewServerResponse: %v", err)
	}
	if r.Status != StatusReferral {
		t.Fatalf("status = %s, want referral", r.Status)
	}
	if r.Starters[0].IPs != nil {
		t.Errorf("glueless starter should have nil IPs, got %v", r.Starters[0].IPs)
	}
}

func TestServerResponseLameReferral(t *testing.T) {
	// A com server "refers" us to an example.org zone: the NS records are
	// out-of-bailiwick so they are discarded, the cache walk falls back to
	// the root NS, and "" is not strictly deeper than "com" → lame.
	msg := newMsg("www.example.com", dns.TypeA, dns.RcodeSuccess)
	msg.Ns = append(msg.Ns, nsRR("example.org", "ns1.example.org"))
	dq := decode(msg, "www.example.com", dns.TypeA, "com")
	if dq.Status != StatusReferral {
		t.Fatalf("decoded status = %s, want referral", dq.Status)
	}

	r, err := NewServerResponse(dq, "a.gtld-servers.net", "192.5.6.30", rootedCache())
	if err != nil {
		t.Fatalf("NewServerResponse: %v", err)
	}
	if r.Status != StatusReferralLame {
		t.Fatalf("status = %s, want referral_lame", r.Status)
	}
	if r.StartersBailiwick != "" {
		t.Errorf("starters bailiwick = %q, want \"\" (root fallback)", r.StartersBailiwick)
	}
	found := false
	for _, w := range dq.Warnings {
		if w == "Referred authority names do not match query cache expectations" {
			found = true
		}
	}
	if !found {
		t.Errorf("expected mismatch warning, got %v", dq.Warnings)
	}
	want := "key:referral_lame:192.0.2.1:a.gtld-servers.net:www.example.com:IN:A:192.5.6.30"
	if got := r.StatsKey(); got != want {
		t.Errorf("stats key = %q, want %q", got, want)
	}
}

func TestServerResponseEqualZoneReferralIsLame(t *testing.T) {
	// Referral back into the SAME zone (com → com) is lame: not strictly deeper.
	msg := newMsg("www.example.com", dns.TypeA, dns.RcodeSuccess)
	msg.Ns = append(msg.Ns, nsRR("com", "b.gtld-servers.net"))
	dq := decode(msg, "www.example.com", dns.TypeA, "com")

	r, err := NewServerResponse(dq, "a.gtld-servers.net", "192.5.6.30", rootedCache())
	if err != nil {
		t.Fatalf("NewServerResponse: %v", err)
	}
	if r.Status != StatusReferralLame {
		t.Fatalf("status = %s, want referral_lame", r.Status)
	}
}

func TestServerResponseRestartStarters(t *testing.T) {
	// A CNAME out of the bailiwick restarts; starters come from the deepest
	// cached zone for the new target (root here).
	msg := newMsg("www.example.com", dns.TypeA, dns.RcodeSuccess)
	msg.Answer = append(msg.Answer, cnameRR("www.example.com", "cdn.example.org"))
	dq := decode(msg, "www.example.com", dns.TypeA, "example.com")
	if dq.Status != StatusRestart {
		t.Fatalf("decoded status = %s, want restart", dq.Status)
	}

	parent := rootedCache()
	parent.Add([]dns.RR{nsRR("example.org", "ns1.example.org"), aRR("ns1.example.org", "9.9.9.9")})
	r, err := NewServerResponse(dq, "ns1.example.com", "", parent)
	if err != nil {
		t.Fatalf("NewServerResponse: %v", err)
	}
	if r.Status != StatusRestart {
		t.Fatalf("status = %s, want restart", r.Status)
	}
	if r.StartersBailiwick != "example.org" {
		t.Errorf("starters bailiwick = %q, want example.org", r.StartersBailiwick)
	}
	if len(r.Starters) != 1 || r.Starters[0].Name != "ns1.example.org" {
		t.Errorf("starters = %v", r.Starters)
	}
}

func TestServerResponseCachesGoodRecordsInChildCache(t *testing.T) {
	parent := rootedCache()
	msg := newMsg("www.example.com", dns.TypeA, dns.RcodeSuccess)
	msg.Ns = append(msg.Ns, nsRR("example.com", "ns1.example.com"))
	msg.Extra = append(msg.Extra,
		aRR("ns1.example.com", "1.2.3.4"),
		aRR("ns1.example.org", "5.6.7.8"), // out of bailiwick — discarded
	)
	dq := decode(msg, "www.example.com", dns.TypeA, "com")

	r, err := NewServerResponse(dq, "a.gtld-servers.net", "", parent)
	if err != nil {
		t.Fatalf("NewServerResponse: %v", err)
	}
	if got := r.Cache.Get("ns1.example.com", dns.ClassINET, dns.TypeA); len(got) != 1 {
		t.Errorf("in-bailiwick glue should be cached, got %v", got)
	}
	if got := r.Cache.Get("ns1.example.org", dns.ClassINET, dns.TypeA); got != nil {
		t.Errorf("out-of-bailiwick record must be discarded, got %v", got)
	}
	// The parent cache stays clean — records live in the response's child.
	if got := parent.Get("example.com", dns.ClassINET, dns.TypeNS); got != nil {
		t.Errorf("parent cache polluted: %v", got)
	}
}

func TestServerResponseExceptionDoesNotCache(t *testing.T) {
	dq := NewDecodedQuery(nil, errTimeout{}, "www.example.com", dns.ClassINET, dns.TypeA, "192.0.2.1", "com")
	r, err := NewServerResponse(dq, "a.gtld-servers.net", "", rootedCache())
	if err != nil {
		t.Fatalf("NewServerResponse: %v", err)
	}
	if r.Status != StatusException {
		t.Fatalf("status = %s, want exception", r.Status)
	}
	want := "key:exception:192.0.2.1:a.gtld-servers.net:www.example.com:IN:A:query timed out"
	if got := r.StatsKey(); got != want {
		t.Errorf("stats key = %q, want %q", got, want)
	}
}

type errTimeout struct{}

func (errTimeout) Error() string { return "query timed out" }

func TestServerResponseAnsweredStatsKey(t *testing.T) {
	msg := newMsg("www.example.com", dns.TypeA, dns.RcodeSuccess)
	msg.Answer = append(msg.Answer, aRR("www.example.com", "93.184.216.34"))
	dq := decode(msg, "www.example.com", dns.TypeA, "example.com")

	r, err := NewServerResponse(dq, "NS1.Example.Com", "", rootedCache())
	if err != nil {
		t.Fatalf("NewServerResponse: %v", err)
	}
	want := "key:answered:192.0.2.1:ns1.example.com:www.example.com:IN:A"
	if got := r.StatsKey(); got != want {
		t.Errorf("stats key = %q, want %q", got, want)
	}
}

func TestNoGlueResponse(t *testing.T) {
	r := NewNoGlueResponse("www.example.com", dns.ClassINET, dns.TypeA, "192.5.6.30", "ns1.example.com", "example.com")
	if r.Status != StatusNoGlue {
		t.Fatalf("status = %s, want noglue", r.Status)
	}
	// NoGlue/Loop use their own field order: ip, qname, qclass, qtype, server, bailiwick.
	want := "key:noglue:192.5.6.30:www.example.com:IN:A:ns1.example.com:example.com"
	if got := r.StatsKey(); got != want {
		t.Errorf("stats key = %q, want %q", got, want)
	}
}

func TestLoopResponse(t *testing.T) {
	r := NewLoopResponse("www.example.com", dns.ClassINET, dns.TypeA, "192.5.6.30", "ns1.example.com", "example.com")
	if r.Status != StatusLoop {
		t.Fatalf("status = %s, want loop", r.Status)
	}
	want := "key:loop:192.5.6.30:www.example.com:IN:A:ns1.example.com:example.com"
	if got := r.StatsKey(); got != want {
		t.Errorf("stats key = %q, want %q", got, want)
	}
}

func TestServerResponseReferralNoRootHintsErrors(t *testing.T) {
	// A lame referral with a completely empty cache chain cannot compute
	// starters; the constructor surfaces the "no root hints" error.
	msg := newMsg("www.example.com", dns.TypeA, dns.RcodeSuccess)
	msg.Ns = append(msg.Ns, nsRR("example.org", "ns1.example.org"))
	dq := decode(msg, "www.example.com", dns.TypeA, "com")
	if _, err := NewServerResponse(dq, "a.gtld-servers.net", "", NewInfoCache(nil)); err == nil {
		t.Fatal("expected error when no NS reachable in cache chain")
	}
}