package rfc2136

import (
	"math"
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"

	"github.com/miekg/dns"
)

// mustRR is a test helper that parses an RR string or fails the test.
// Used widely in zonefile + update tests.
func mustRR(t *testing.T, s string) dns.RR {
	t.Helper()
	rr, err := dns.NewRR(s)
	if err != nil {
		t.Fatalf("failed to parse RR %q: %v", s, err)
	}
	return rr
}

func TestZoneFile_LoadRRs(t *testing.T) {
	dir := withTempZonesDir(t, "auth.example.com")
	zf := openZoneFile(filepath.Join(dir, "auth.example.com.zone"), "auth.example.com.")

	rrs, _, err := zf.loadRRs()
	if err != nil {
		t.Fatalf("loadRRs: %v", err)
	}
	if len(rrs) < 2 {
		t.Fatalf("expected >=2 RRs (SOA + NS), got %d", len(rrs))
	}
	// First RR should be the SOA.
	if _, ok := rrs[0].(*dns.SOA); !ok {
		t.Errorf("first RR is %T, want SOA", rrs[0])
	}
}

func TestZoneFile_LoadRRs_MissingFile(t *testing.T) {
	zf := openZoneFile("/nope/missing.zone", "missing.")
	if _, _, err := zf.loadRRs(); err == nil {
		t.Errorf("expected error loading missing file, got nil")
	}
}

func TestLookupIn_CaseInsensitive(t *testing.T) {
	rrs := []dns.RR{
		mustRR(t, `FOO.example.com. 60 IN TXT "hello"`),
	}
	if got := lookupIn(rrs, "foo.EXAMPLE.com.", dns.TypeTXT); len(got) != 1 {
		t.Errorf("case-insensitive lookup failed: %d results", len(got))
	}
}

func TestLookupIn_WrongTypeReturnsEmpty(t *testing.T) {
	rrs := []dns.RR{mustRR(t, `foo.example.com. 60 IN A 192.0.2.1`)}
	if got := lookupIn(rrs, "foo.example.com.", dns.TypeTXT); len(got) != 0 {
		t.Errorf("wrong-type lookup returned %d results, want 0", len(got))
	}
}

func TestNameExistsIn(t *testing.T) {
	rrs := []dns.RR{mustRR(t, `foo.example.com. 60 IN A 192.0.2.1`)}
	if !nameExistsIn(rrs, "foo.example.com.") {
		t.Errorf("nameExistsIn returned false for present name")
	}
	if nameExistsIn(rrs, "bar.example.com.") {
		t.Errorf("nameExistsIn returned true for absent name")
	}
}

func TestRemoveRRsetFrom(t *testing.T) {
	rrs := []dns.RR{
		mustRR(t, `foo.example.com. 60 IN TXT "a"`),
		mustRR(t, `foo.example.com. 60 IN TXT "b"`),
		mustRR(t, `foo.example.com. 60 IN A 192.0.2.1`),
		mustRR(t, `bar.example.com. 60 IN A 192.0.2.2`),
	}
	out := removeRRsetFrom(rrs, "foo.example.com.", dns.TypeTXT)
	if len(out) != 2 {
		t.Errorf("after removing TXT rrset, got %d records, want 2", len(out))
	}
	// The remaining records: foo's A + bar's A
	for _, rr := range out {
		if rr.Header().Rrtype == dns.TypeTXT {
			t.Errorf("a TXT slipped through removal: %s", rr.String())
		}
	}
}

func TestRemoveRRFrom_ExactMatchOnly(t *testing.T) {
	rrs := []dns.RR{
		mustRR(t, `foo.example.com. 60 IN TXT "keep"`),
		mustRR(t, `foo.example.com. 60 IN TXT "drop"`),
	}
	out := removeRRFrom(rrs, mustRR(t, `foo.example.com. 60 IN TXT "drop"`))
	if len(out) != 1 || out[0].(*dns.TXT).Txt[0] != "keep" {
		t.Errorf("removeRRFrom wrong result: %v", out)
	}
}

func TestRemoveNameFrom(t *testing.T) {
	rrs := []dns.RR{
		mustRR(t, `foo.example.com. 60 IN TXT "x"`),
		mustRR(t, `foo.example.com. 60 IN A 192.0.2.1`),
		mustRR(t, `bar.example.com. 60 IN A 192.0.2.2`),
	}
	out := removeNameFrom(rrs, "foo.example.com.")
	if len(out) != 1 || out[0].Header().Name != "bar.example.com." {
		t.Errorf("removeNameFrom left %v, want only bar", out)
	}
}

func TestAddRRTo_Dedupes(t *testing.T) {
	rrs := []dns.RR{mustRR(t, `foo.example.com. 60 IN TXT "same"`)}
	out := addRRTo(rrs, mustRR(t, `foo.example.com. 60 IN TXT "same"`))
	if len(out) != 1 {
		t.Errorf("identical RR was duplicated: %v", out)
	}
}

// bumpSerial tests below pin the YYMMDD*10000+NNNN encoding. For
// 2026-05-21 (used as `now` in most cases): YYMMDD=260521, baseline
// "today, NNNN=0001" = 2,605,210,001.

func TestBumpSerial_SameDay_NNNNIncrement(t *testing.T) {
	rrs := []dns.RR{
		&dns.SOA{Hdr: dns.RR_Header{Name: "example.com.", Rrtype: dns.TypeSOA},
			Serial: 2605210105}, // today, NNNN=0105
	}
	now := time.Date(2026, 5, 21, 12, 0, 0, 0, time.UTC)
	if err := bumpSerial(rrs, now); err != nil {
		t.Fatalf("bumpSerial: %v", err)
	}
	if got := rrs[0].(*dns.SOA).Serial; got != 2605210106 {
		t.Errorf("Serial = %d, want 2605210106", got)
	}
}

func TestBumpSerial_NewDay_DateAdvancesNNNN0001(t *testing.T) {
	rrs := []dns.RR{
		&dns.SOA{Hdr: dns.RR_Header{Name: "example.com.", Rrtype: dns.TypeSOA},
			Serial: 2605209999}, // exhausted yesterday (in new format)
	}
	now := time.Date(2026, 5, 21, 1, 0, 0, 0, time.UTC)
	if err := bumpSerial(rrs, now); err != nil {
		t.Fatalf("bumpSerial: %v", err)
	}
	if got := rrs[0].(*dns.SOA).Serial; got != 2605210001 {
		t.Errorf("Serial = %d, want 2605210001 (today, NNNN=0001)", got)
	}
}

func TestBumpSerial_NNNN9999_RollsToNextEncodedDay(t *testing.T) {
	rrs := []dns.RR{
		&dns.SOA{Hdr: dns.RR_Header{Name: "example.com.", Rrtype: dns.TypeSOA},
			Serial: 2605219999}, // today, NNNN=9999 (the burst-day overflow case)
	}
	now := time.Date(2026, 5, 21, 1, 0, 0, 0, time.UTC)
	if err := bumpSerial(rrs, now); err != nil {
		t.Fatalf("bumpSerial: %v", err)
	}
	if got := rrs[0].(*dns.SOA).Serial; got != 2605220001 {
		t.Errorf("Serial = %d, want 2605220001 (next encoded day, NNNN=0001)", got)
	}
}

func TestBumpSerial_FutureEncodedDate_DoesNotRegress(t *testing.T) {
	// Reproduces the bug from 2026-05-22: an earlier bumpSerial would
	// downgrade a future-encoded serial back to today's NNNN=0001. Now,
	// future-encoded serials are honoured: their NNNN increments.
	rrs := []dns.RR{
		&dns.SOA{Hdr: dns.RR_Header{Name: "example.com.", Rrtype: dns.TypeSOA},
			Serial: 2605220500}, // tomorrow (encoded), NNNN=0500
	}
	now := time.Date(2026, 5, 21, 1, 0, 0, 0, time.UTC)
	if err := bumpSerial(rrs, now); err != nil {
		t.Fatalf("bumpSerial: %v", err)
	}
	if got := rrs[0].(*dns.SOA).Serial; got != 2605220501 {
		t.Errorf("Serial = %d, want 2605220501 (future date NNNN+1, no regression)", got)
	}
}

func TestBumpSerial_LegacyYYYYMMDDNNFormat_MigratesForward(t *testing.T) {
	// The migration path: any production zone whose SOA serial is in the
	// old 10-digit YYYYMMDDNN format (e.g., 2026052299) gets numerically
	// crushed by today's YYMMDDNNNN minimum, so the "older/unparseable"
	// branch fires and rewrites in place.
	rrs := []dns.RR{
		&dns.SOA{Hdr: dns.RR_Header{Name: "example.com.", Rrtype: dns.TypeSOA},
			Serial: 2026052299}, // legacy YYYYMMDDNN, exhausted day
	}
	now := time.Date(2026, 5, 22, 12, 0, 0, 0, time.UTC) // 2026-05-22
	if err := bumpSerial(rrs, now); err != nil {
		t.Fatalf("bumpSerial: %v", err)
	}
	got := rrs[0].(*dns.SOA).Serial
	if got != 2605220001 {
		t.Errorf("Serial = %d, want 2605220001 (migrated to new format)", got)
	}
	if got <= 2026052299 {
		t.Errorf("migration regressed serial: %d <= legacy %d", got, 2026052299)
	}
}

func TestBumpSerial_NonCalVerFormat_ResetsToToday(t *testing.T) {
	rrs := []dns.RR{
		&dns.SOA{Hdr: dns.RR_Header{Name: "example.com.", Rrtype: dns.TypeSOA},
			Serial: 12345}, // random small value, not CalVer
	}
	now := time.Date(2026, 5, 21, 1, 0, 0, 0, time.UTC)
	if err := bumpSerial(rrs, now); err != nil {
		t.Fatalf("bumpSerial: %v", err)
	}
	if got := rrs[0].(*dns.SOA).Serial; got != 2605210001 {
		t.Errorf("Serial = %d, want 2605210001", got)
	}
}

// TestBumpSerial_MaxUint32_RefusesWrap covers H5: the defensive
// branch must not wrap soa.Serial to 0. Wrap-to-0 makes downstream
// secondaries treat the zone as reset per RFC 1982 and refuse to AXFR
// the new value, taking the zone dark.
func TestBumpSerial_MaxUint32_RefusesWrap(t *testing.T) {
	rrs := []dns.RR{
		&dns.SOA{Hdr: dns.RR_Header{Name: "example.com.", Rrtype: dns.TypeSOA},
			Serial: math.MaxUint32},
	}
	now := time.Date(2026, 5, 22, 1, 0, 0, 0, time.UTC)
	if err := bumpSerial(rrs, now); err == nil {
		t.Errorf("bumpSerial accepted MaxUint32; expected refusal to prevent wrap-to-0")
	}
	if got := rrs[0].(*dns.SOA).Serial; got == 0 {
		t.Errorf("Serial wrapped to 0 (catastrophic): %d", got)
	}
}

// TestLoadRRs_NoSOA_Refused covers H4: a zone file that's missing its
// SOA (because the parser ate it on a malformed prior line, or because
// it was never there) must fail loadRRs rather than be silently treated
// as a valid empty-of-SOA zone.
func TestLoadRRs_NoSOA_Refused(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "noSoA.example.com.zone")
	content := "$ORIGIN noSoA.example.com.\nfoo.noSoA.example.com. 60 IN A 192.0.2.1\n"
	if err := os.WriteFile(path, []byte(content), 0644); err != nil {
		t.Fatalf("write fixture: %v", err)
	}
	zf := openZoneFile(path, "noSoA.example.com.")
	if _, _, err := zf.loadRRs(); err == nil {
		t.Errorf("loadRRs accepted SOA-less zone file; expected refusal")
	}
}

// TestLoadRRs_MultipleSOAs_Refused covers H3: two SOAs at the apex
// produce inconsistent zone state visible to AXFR clients. We refuse
// to operate on such a file rather than bumping only the first SOA.
func TestLoadRRs_MultipleSOAs_Refused(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "dupe.example.com.zone")
	content := `$ORIGIN dupe.example.com.
dupe.example.com. 3600 IN SOA ns.example. admin.example. 1 60 60 60 60
dupe.example.com. 3600 IN SOA ns.example. admin.example. 2 60 60 60 60
dupe.example.com. 3600 IN NS ns.example.
`
	if err := os.WriteFile(path, []byte(content), 0644); err != nil {
		t.Fatalf("write fixture: %v", err)
	}
	zf := openZoneFile(path, "dupe.example.com.")
	if _, _, err := zf.loadRRs(); err == nil {
		t.Errorf("loadRRs accepted dual-SOA zone; expected refusal")
	}
}

// TestLoadRRs_NonApexSOA_Refused covers H3: an SOA owned by a name
// other than the zone apex is a parse-error red flag and must be
// refused, not silently bumped.
func TestLoadRRs_NonApexSOA_Refused(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "weird.example.com.zone")
	content := `$ORIGIN weird.example.com.
sub.weird.example.com. 3600 IN SOA ns.example. admin.example. 1 60 60 60 60
weird.example.com. 3600 IN NS ns.example.
`
	if err := os.WriteFile(path, []byte(content), 0644); err != nil {
		t.Fatalf("write fixture: %v", err)
	}
	zf := openZoneFile(path, "weird.example.com.")
	if _, _, err := zf.loadRRs(); err == nil {
		t.Errorf("loadRRs accepted non-apex SOA; expected refusal")
	}
}

func TestBumpSerial_NoSOA_ReturnsError(t *testing.T) {
	rrs := []dns.RR{mustRR(t, `foo.example.com. 60 IN A 192.0.2.1`)}
	now := time.Now()
	if err := bumpSerial(rrs, now); err == nil {
		t.Errorf("expected error when no SOA in zone, got nil")
	}
}

func TestZoneFile_WriteAtomic_RoundTrip(t *testing.T) {
	dir := withTempZonesDir(t, "auth.example.com")
	path := filepath.Join(dir, "auth.example.com.zone")
	zf := openZoneFile(path, "auth.example.com.")
	zf.AutoCommit = false // not testing commit here

	rrs, _, err := zf.loadRRs()
	if err != nil {
		t.Fatalf("initial load: %v", err)
	}
	originalCount := len(rrs)

	// Add a record + write.
	rrs = addRRTo(rrs, mustRR(t, `new.auth.example.com. 60 IN TXT "added"`))
	if err := zf.writeAtomic(rrs, time.Now()); err != nil {
		t.Fatalf("writeAtomic: %v", err)
	}

	// Re-load and verify.
	after, _, err := zf.loadRRs()
	if err != nil {
		t.Fatalf("re-load: %v", err)
	}
	if len(after) != originalCount+1 {
		t.Errorf("RR count = %d, want %d", len(after), originalCount+1)
	}
	found := false
	for _, rr := range after {
		if txt, ok := rr.(*dns.TXT); ok && txt.Hdr.Name == "new.auth.example.com." {
			found = true
			break
		}
	}
	if !found {
		t.Errorf("added TXT not in reloaded zone")
	}
}

func TestZoneFile_WriteAtomic_LeavesNoTempFile(t *testing.T) {
	dir := withTempZonesDir(t, "auth.example.com")
	path := filepath.Join(dir, "auth.example.com.zone")
	zf := openZoneFile(path, "auth.example.com.")
	zf.AutoCommit = false

	rrs, _, _ := zf.loadRRs()
	_ = zf.writeAtomic(rrs, time.Now())

	// No .rfc2136-*.zone temp files should remain.
	matches, _ := filepath.Glob(filepath.Join(dir, ".rfc2136-*.zone"))
	if len(matches) != 0 {
		t.Errorf("temp files leaked: %v", matches)
	}
}

// TestZoneFile_CheckUnchanged_DetectsExternalModification covers H1:
// between loadRRs and the next writeAtomic, if anything (rsync, manual
// edit, git checkout) clobbered the file, checkUnchanged returns an
// error so the caller refuses the UPDATE instead of losing the
// external write.
func TestZoneFile_CheckUnchanged_DetectsExternalModification(t *testing.T) {
	dir := withTempZonesDir(t, "auth.example.com")
	path := filepath.Join(dir, "auth.example.com.zone")
	zf := openZoneFile(path, "auth.example.com.")
	zf.AutoCommit = false

	_, snap, err := zf.loadRRs()
	if err != nil {
		t.Fatalf("loadRRs: %v", err)
	}

	// Pristine snapshot — checkUnchanged should pass.
	if err := zf.checkUnchanged(snap); err != nil {
		t.Errorf("pristine snapshot rejected: %v", err)
	}

	// Simulate an external editor clobbering the file (rsync-style:
	// new content, different size, mtime advances).
	time.Sleep(10 * time.Millisecond) // ensure mtime differs
	if err := os.WriteFile(path, []byte("; external edit\n$ORIGIN auth.example.com.\nauth.example.com. 3600 IN SOA ns.example. admin.example. 1 60 60 60 60\n"), 0644); err != nil {
		t.Fatalf("simulated external edit: %v", err)
	}

	if err := zf.checkUnchanged(snap); err == nil {
		t.Errorf("checkUnchanged accepted modified file; expected concurrent-modification error")
	}
}

func TestZoneFile_WriteAtomic_FileEndsWithNewline(t *testing.T) {
	dir := withTempZonesDir(t, "auth.example.com")
	path := filepath.Join(dir, "auth.example.com.zone")
	zf := openZoneFile(path, "auth.example.com.")
	zf.AutoCommit = false

	rrs, _, _ := zf.loadRRs()
	_ = zf.writeAtomic(rrs, time.Now())

	data, _ := os.ReadFile(path)
	if !strings.HasSuffix(string(data), "\n") {
		t.Errorf("written file should end with newline; tail: %q",
			data[max(0, len(data)-20):])
	}
}

func max(a, b int) int {
	if a > b {
		return a
	}
	return b
}