dnswatcher/internal/state/state_test.go

package state_test

import (
	"encoding/json"
	"os"
	"path/filepath"
	"sync"
	"testing"
	"time"

	"sneak.berlin/go/dnswatcher/internal/state"
)

const testHostname = "www.example.com"

// populateState fills a State with representative test data across all categories.
func populateState(t *testing.T, s *state.State) {
	t.Helper()

	now := time.Now().UTC().Truncate(time.Second)

	s.SetDomainState("example.com", &state.DomainState{
		Nameservers: []string{"ns1.example.com.", "ns2.example.com."},
		LastChecked: now,
	})

	s.SetDomainState("example.org", &state.DomainState{
		Nameservers: []string{"ns1.example.org."},
		LastChecked: now,
	})

	s.SetHostnameState(testHostname, &state.HostnameState{
		RecordsByNameserver: map[string]*state.NameserverRecordState{
			"ns1.example.com.": {
				Records: map[string][]string{
					"A":    {"93.184.216.34"},
					"AAAA": {"2606:2800:220:1:248:1893:25c8:1946"},
				},
				Status:      "ok",
				LastChecked: now,
			},
			"ns2.example.com.": {
				Records: map[string][]string{
					"A": {"93.184.216.34"},
				},
				Status:      "ok",
				LastChecked: now,
			},
		},
		LastChecked: now,
	})

	s.SetPortState("93.184.216.34:80", &state.PortState{
		Open:        true,
		Hostnames:   []string{testHostname},
		LastChecked: now,
	})

	s.SetPortState("93.184.216.34:443", &state.PortState{
		Open:        true,
		Hostnames:   []string{testHostname, "api.example.com"},
		LastChecked: now,
	})

	s.SetCertificateState("93.184.216.34:443:www.example.com", &state.CertificateState{
		CommonName:              testHostname,
		Issuer:                  "DigiCert TLS RSA SHA256 2020 CA1",
		NotAfter:                now.Add(365 * 24 * time.Hour),
		SubjectAlternativeNames: []string{testHostname, "example.com"},
		Status:                  "ok",
		LastChecked:             now,
	})
}

// TestSaveLoadRoundTrip_Domains verifies domain data survives a save/load cycle.
func TestSaveLoadRoundTrip_Domains(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()
	s := state.NewForTestWithDataDir(dir)

	populateState(t, s)

	err := s.Save()
	if err != nil {
		t.Fatalf("Save() error: %v", err)
	}

	loaded := state.NewForTestWithDataDir(dir)

	err = loaded.Load()
	if err != nil {
		t.Fatalf("Load() error: %v", err)
	}

	snap := loaded.GetSnapshot()

	if len(snap.Domains) != 2 {
		t.Fatalf("expected 2 domains, got %d", len(snap.Domains))
	}

	dom, ok := snap.Domains["example.com"]
	if !ok {
		t.Fatal("missing domain example.com")
	}

	if len(dom.Nameservers) != 2 {
		t.Errorf("expected 2 nameservers, got %d", len(dom.Nameservers))
	}
}

// TestSaveLoadRoundTrip_Hostnames verifies hostname data survives a save/load cycle.
func TestSaveLoadRoundTrip_Hostnames(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()
	s := state.NewForTestWithDataDir(dir)

	populateState(t, s)

	err := s.Save()
	if err != nil {
		t.Fatalf("Save() error: %v", err)
	}

	loaded := state.NewForTestWithDataDir(dir)

	err = loaded.Load()
	if err != nil {
		t.Fatalf("Load() error: %v", err)
	}

	snap := loaded.GetSnapshot()

	if len(snap.Hostnames) != 1 {
		t.Fatalf("expected 1 hostname, got %d", len(snap.Hostnames))
	}

	hn, ok := snap.Hostnames[testHostname]
	if !ok {
		t.Fatal("missing hostname")
	}

	if len(hn.RecordsByNameserver) != 2 {
		t.Errorf("expected 2 NS entries, got %d", len(hn.RecordsByNameserver))
	}

	verifyNS1Records(t, hn)
}

// verifyNS1Records checks the ns1.example.com. records in the loaded hostname state.
func verifyNS1Records(t *testing.T, hn *state.HostnameState) {
	t.Helper()

	ns1, ok := hn.RecordsByNameserver["ns1.example.com."]
	if !ok {
		t.Fatal("missing nameserver ns1.example.com.")
	}

	aRecords := ns1.Records["A"]
	if len(aRecords) != 1 || aRecords[0] != "93.184.216.34" {
		t.Errorf("ns1 A records: got %v", aRecords)
	}

	aaaaRecords := ns1.Records["AAAA"]
	if len(aaaaRecords) != 1 || aaaaRecords[0] != "2606:2800:220:1:248:1893:25c8:1946" {
		t.Errorf("ns1 AAAA records: got %v", aaaaRecords)
	}

	if ns1.Status != "ok" {
		t.Errorf("ns1 status: got %q, want %q", ns1.Status, "ok")
	}
}

// TestSaveLoadRoundTrip_Ports verifies port data survives a save/load cycle.
func TestSaveLoadRoundTrip_Ports(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()
	s := state.NewForTestWithDataDir(dir)

	populateState(t, s)

	err := s.Save()
	if err != nil {
		t.Fatalf("Save() error: %v", err)
	}

	loaded := state.NewForTestWithDataDir(dir)

	err = loaded.Load()
	if err != nil {
		t.Fatalf("Load() error: %v", err)
	}

	snap := loaded.GetSnapshot()

	if len(snap.Ports) != 2 {
		t.Fatalf("expected 2 ports, got %d", len(snap.Ports))
	}

	port443, ok := snap.Ports["93.184.216.34:443"]
	if !ok {
		t.Fatal("missing port 93.184.216.34:443")
	}

	if !port443.Open {
		t.Error("port 443: expected open")
	}

	if len(port443.Hostnames) != 2 {
		t.Errorf("expected 2 hostnames, got %d", len(port443.Hostnames))
	}
}

// TestSaveLoadRoundTrip_Certificates verifies certificate data survives a save/load cycle.
func TestSaveLoadRoundTrip_Certificates(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()
	s := state.NewForTestWithDataDir(dir)

	populateState(t, s)

	err := s.Save()
	if err != nil {
		t.Fatalf("Save() error: %v", err)
	}

	loaded := state.NewForTestWithDataDir(dir)

	err = loaded.Load()
	if err != nil {
		t.Fatalf("Load() error: %v", err)
	}

	snap := loaded.GetSnapshot()

	if len(snap.Certificates) != 1 {
		t.Fatalf("expected 1 certificate, got %d", len(snap.Certificates))
	}

	cert, ok := snap.Certificates["93.184.216.34:443:www.example.com"]
	if !ok {
		t.Fatal("missing certificate")
	}

	if cert.CommonName != testHostname {
		t.Errorf("cert CN: got %q", cert.CommonName)
	}

	if cert.Issuer != "DigiCert TLS RSA SHA256 2020 CA1" {
		t.Errorf("cert issuer: got %q", cert.Issuer)
	}

	if len(cert.SubjectAlternativeNames) != 2 {
		t.Errorf("cert SANs: expected 2, got %d", len(cert.SubjectAlternativeNames))
	}

	if cert.Status != "ok" {
		t.Errorf("cert status: got %q", cert.Status)
	}
}

// TestSaveCreatesDirectory verifies Save creates the data directory if missing.
func TestSaveCreatesDirectory(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()
	nested := filepath.Join(dir, "nested", "deep")

	s := state.NewForTestWithDataDir(nested)

	err := s.Save()
	if err != nil {
		t.Fatalf("Save() error: %v", err)
	}

	statePath := filepath.Join(nested, "state.json")

	info, err := os.Stat(statePath)
	if err != nil {
		t.Fatalf("state file not found: %v", err)
	}

	if info.Size() == 0 {
		t.Error("state file is empty")
	}
}

// TestSaveAtomicWrite verifies the atomic write pattern (no leftover temp files).
func TestSaveAtomicWrite(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()
	s := state.NewForTestWithDataDir(dir)

	populateState(t, s)

	err := s.Save()
	if err != nil {
		t.Fatalf("Save() error: %v", err)
	}

	statePath := filepath.Join(dir, "state.json")
	tmpPath := statePath + ".tmp"

	// No .tmp file should remain after successful save.
	_, err = os.Stat(tmpPath)
	if !os.IsNotExist(err) {
		t.Error("temp file should not exist after successful save")
	}

	// Modify state and save again; verify updated content.
	s.SetDomainState("new.example.com", &state.DomainState{
		Nameservers: []string{"ns1.new.example.com."},
		LastChecked: time.Now().UTC(),
	})

	err = s.Save()
	if err != nil {
		t.Fatalf("second Save() error: %v", err)
	}

	_, err = os.Stat(tmpPath)
	if !os.IsNotExist(err) {
		t.Error("temp file should not exist after second save")
	}

	// Verify new domain is present by loading.
	loaded := state.NewForTestWithDataDir(dir)

	err = loaded.Load()
	if err != nil {
		t.Fatalf("Load() error: %v", err)
	}

	_, ok := loaded.GetDomainState("new.example.com")
	if !ok {
		t.Error("new domain not found after second save")
	}
}

// TestLoadMissingFile verifies that loading a nonexistent file is not an error.
func TestLoadMissingFile(t *testing.T) {
	t.Parallel()

	s := state.NewForTestWithDataDir(t.TempDir())

	err := s.Load()
	if err != nil {
		t.Fatalf("Load() with missing file should not error: %v", err)
	}

	snap := s.GetSnapshot()

	if len(snap.Domains) != 0 {
		t.Error("expected empty domains")
	}

	if len(snap.Hostnames) != 0 {
		t.Error("expected empty hostnames")
	}

	if len(snap.Ports) != 0 {
		t.Error("expected empty ports")
	}

	if len(snap.Certificates) != 0 {
		t.Error("expected empty certificates")
	}
}

// TestLoadCorruptFile verifies that a corrupt state file returns an error.
func TestLoadCorruptFile(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()

	err := os.WriteFile(
		filepath.Join(dir, "state.json"),
		[]byte("not valid json{{{"),
		0o600,
	)
	if err != nil {
		t.Fatalf("writing corrupt file: %v", err)
	}

	s := state.NewForTestWithDataDir(dir)

	err = s.Load()
	if err == nil {
		t.Fatal("Load() should return error for corrupt file")
	}
}

// TestLoadEmptyFile verifies that an empty state file returns an error.
func TestLoadEmptyFile(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()

	err := os.WriteFile(filepath.Join(dir, "state.json"), []byte(""), 0o600)
	if err != nil {
		t.Fatalf("writing empty file: %v", err)
	}

	s := state.NewForTestWithDataDir(dir)

	err = s.Load()
	if err == nil {
		t.Fatal("Load() should return error for empty file")
	}
}

// TestLoadReadPermissionError verifies that an unreadable state file returns an error.
func TestLoadReadPermissionError(t *testing.T) {
	t.Parallel()

	if os.Getuid() == 0 {
		t.Skip("skipping permission test when running as root")
	}

	dir := t.TempDir()
	statePath := filepath.Join(dir, "state.json")

	err := os.WriteFile(statePath, []byte("{}"), 0o600)
	if err != nil {
		t.Fatalf("writing file: %v", err)
	}

	err = os.Chmod(statePath, 0o000)
	if err != nil {
		t.Fatalf("chmod: %v", err)
	}

	t.Cleanup(func() {
		_ = os.Chmod(statePath, 0o600)
	})

	s := state.NewForTestWithDataDir(dir)

	err = s.Load()
	if err == nil {
		t.Fatal("Load() should return error for unreadable file")
	}
}

// TestSaveWritePermissionError verifies that Save returns an error
// when the directory is not writable.
func TestSaveWritePermissionError(t *testing.T) {
	t.Parallel()

	if os.Getuid() == 0 {
		t.Skip("skipping permission test when running as root")
	}

	dir := t.TempDir()
	dataDir := filepath.Join(dir, "readonly")

	err := os.MkdirAll(dataDir, 0o700)
	if err != nil {
		t.Fatalf("creating dir: %v", err)
	}

	//nolint:gosec // intentionally making dir read-only+execute for test
	err = os.Chmod(dataDir, 0o500)
	if err != nil {
		t.Fatalf("chmod: %v", err)
	}

	t.Cleanup(func() {
		//nolint:gosec // restoring write permission for cleanup
		_ = os.Chmod(dataDir, 0o700)
	})

	s := state.NewForTestWithDataDir(dataDir)

	err = s.Save()
	if err == nil {
		t.Fatal("Save() should return error for read-only directory")
	}
}

// TestPortStateUnmarshalJSON_NewFormat verifies deserialization of the
// current multi-hostname format.
func TestPortStateUnmarshalJSON_NewFormat(t *testing.T) {
	t.Parallel()

	data := []byte(`{
		"open": true,
		"hostnames": ["www.example.com", "api.example.com"],
		"lastChecked": "2026-02-19T12:00:00Z"
	}`)

	var ps state.PortState

	err := json.Unmarshal(data, &ps)
	if err != nil {
		t.Fatalf("Unmarshal error: %v", err)
	}

	if !ps.Open {
		t.Error("expected open=true")
	}

	if len(ps.Hostnames) != 2 {
		t.Fatalf("expected 2 hostnames, got %d", len(ps.Hostnames))
	}

	if ps.Hostnames[0] != testHostname {
		t.Errorf("hostname[0]: got %q", ps.Hostnames[0])
	}

	if ps.Hostnames[1] != "api.example.com" {
		t.Errorf("hostname[1]: got %q", ps.Hostnames[1])
	}

	if ps.LastChecked.IsZero() {
		t.Error("expected non-zero LastChecked")
	}
}

// TestPortStateUnmarshalJSON_OldFormat verifies backward-compatible
// deserialization of the old single-hostname format.
func TestPortStateUnmarshalJSON_OldFormat(t *testing.T) {
	t.Parallel()

	data := []byte(`{
		"open": false,
		"hostname": "legacy.example.com",
		"lastChecked": "2026-01-15T10:30:00Z"
	}`)

	var ps state.PortState

	err := json.Unmarshal(data, &ps)
	if err != nil {
		t.Fatalf("Unmarshal error: %v", err)
	}

	if ps.Open {
		t.Error("expected open=false")
	}

	if len(ps.Hostnames) != 1 {
		t.Fatalf("expected 1 hostname, got %d", len(ps.Hostnames))
	}

	if ps.Hostnames[0] != "legacy.example.com" {
		t.Errorf("hostname: got %q", ps.Hostnames[0])
	}
}

// TestPortStateUnmarshalJSON_EmptyHostnames verifies that when neither
// hostnames nor hostname is present, Hostnames remains nil.
func TestPortStateUnmarshalJSON_EmptyHostnames(t *testing.T) {
	t.Parallel()

	data := []byte(`{
		"open": true,
		"lastChecked": "2026-02-19T12:00:00Z"
	}`)

	var ps state.PortState

	err := json.Unmarshal(data, &ps)
	if err != nil {
		t.Fatalf("Unmarshal error: %v", err)
	}

	if len(ps.Hostnames) != 0 {
		t.Errorf("expected empty hostnames, got %v", ps.Hostnames)
	}
}

// TestPortStateUnmarshalJSON_InvalidJSON verifies that invalid JSON returns an error.
func TestPortStateUnmarshalJSON_InvalidJSON(t *testing.T) {
	t.Parallel()

	data := []byte(`{invalid json}`)

	var ps state.PortState

	err := json.Unmarshal(data, &ps)
	if err == nil {
		t.Fatal("expected error for invalid JSON")
	}
}

// TestPortStateUnmarshalJSON_BothFormats verifies that when both "hostnames"
// and "hostname" are present, the new format takes precedence.
func TestPortStateUnmarshalJSON_BothFormats(t *testing.T) {
	t.Parallel()

	data := []byte(`{
		"open": true,
		"hostnames": ["new.example.com"],
		"hostname": "old.example.com",
		"lastChecked": "2026-02-19T12:00:00Z"
	}`)

	var ps state.PortState

	err := json.Unmarshal(data, &ps)
	if err != nil {
		t.Fatalf("Unmarshal error: %v", err)
	}

	// When hostnames is non-empty, the old hostname field is ignored.
	if len(ps.Hostnames) != 1 {
		t.Fatalf("expected 1 hostname, got %d", len(ps.Hostnames))
	}

	if ps.Hostnames[0] != "new.example.com" {
		t.Errorf("hostname: got %q, want %q", ps.Hostnames[0], "new.example.com")
	}
}

// TestGetSnapshot_ReturnsCopy verifies that GetSnapshot returns a value copy.
func TestGetSnapshot_ReturnsCopy(t *testing.T) {
	t.Parallel()

	s := state.NewForTest()

	populateState(t, s)

	snap := s.GetSnapshot()

	// Mutate the returned snapshot's map.
	snap.Domains["mutated.example.com"] = &state.DomainState{
		Nameservers: []string{"ns1.mutated.com."},
	}

	// The original domain data should still be accessible.
	_, ok := s.GetDomainState("example.com")
	if !ok {
		t.Error("original domain should still exist")
	}
}

// TestDomainState_GetSet tests domain state getter and setter.
func TestDomainState_GetSet(t *testing.T) {
	t.Parallel()

	s := state.NewForTest()

	// Get on missing key returns false.
	_, ok := s.GetDomainState("nonexistent.com")
	if ok {
		t.Error("expected false for missing domain")
	}

	now := time.Now().UTC().Truncate(time.Second)
	ds := &state.DomainState{
		Nameservers: []string{"ns1.test.com."},
		LastChecked: now,
	}

	s.SetDomainState("test.com", ds)

	got, ok := s.GetDomainState("test.com")
	if !ok {
		t.Fatal("expected true for existing domain")
	}

	if len(got.Nameservers) != 1 || got.Nameservers[0] != "ns1.test.com." {
		t.Errorf("nameservers: got %v", got.Nameservers)
	}

	if !got.LastChecked.Equal(now) {
		t.Errorf("lastChecked: got %v, want %v", got.LastChecked, now)
	}

	// Overwrite.
	ds2 := &state.DomainState{
		Nameservers: []string{"ns1.test.com.", "ns2.test.com."},
		LastChecked: now.Add(time.Hour),
	}

	s.SetDomainState("test.com", ds2)

	got2, ok := s.GetDomainState("test.com")
	if !ok {
		t.Fatal("expected true after overwrite")
	}

	if len(got2.Nameservers) != 2 {
		t.Errorf("expected 2 nameservers after overwrite, got %d", len(got2.Nameservers))
	}
}

// TestHostnameState_GetSet tests hostname state getter and setter.
func TestHostnameState_GetSet(t *testing.T) {
	t.Parallel()

	s := state.NewForTest()

	_, ok := s.GetHostnameState("missing.example.com")
	if ok {
		t.Error("expected false for missing hostname")
	}

	now := time.Now().UTC().Truncate(time.Second)
	hs := &state.HostnameState{
		RecordsByNameserver: map[string]*state.NameserverRecordState{
			"ns1.example.com.": {
				Records:     map[string][]string{"A": {"1.2.3.4"}},
				Status:      "ok",
				LastChecked: now,
			},
		},
		LastChecked: now,
	}

	s.SetHostnameState(testHostname, hs)

	got, ok := s.GetHostnameState(testHostname)
	if !ok {
		t.Fatal("expected true for existing hostname")
	}

	nsState, ok := got.RecordsByNameserver["ns1.example.com."]
	if !ok {
		t.Fatal("missing nameserver entry")
	}

	if nsState.Status != "ok" {
		t.Errorf("status: got %q", nsState.Status)
	}

	aRecords := nsState.Records["A"]
	if len(aRecords) != 1 || aRecords[0] != "1.2.3.4" {
		t.Errorf("A records: got %v", aRecords)
	}
}

// TestPortState_GetSetDelete tests port state getter, setter, and deletion.
func TestPortState_GetSetDelete(t *testing.T) {
	t.Parallel()

	s := state.NewForTest()

	_, ok := s.GetPortState("1.2.3.4:80")
	if ok {
		t.Error("expected false for missing port")
	}

	now := time.Now().UTC().Truncate(time.Second)
	ps := &state.PortState{
		Open:        true,
		Hostnames:   []string{testHostname},
		LastChecked: now,
	}

	s.SetPortState("1.2.3.4:80", ps)

	got, ok := s.GetPortState("1.2.3.4:80")
	if !ok {
		t.Fatal("expected true for existing port")
	}

	if !got.Open {
		t.Error("expected open=true")
	}

	// Delete the port state.
	s.DeletePortState("1.2.3.4:80")

	_, ok = s.GetPortState("1.2.3.4:80")
	if ok {
		t.Error("expected false after delete")
	}
}

// TestGetAllPortKeys tests retrieving all port state keys.
func TestGetAllPortKeys(t *testing.T) {
	t.Parallel()

	s := state.NewForTest()

	keys := s.GetAllPortKeys()
	if len(keys) != 0 {
		t.Errorf("expected 0 keys, got %d", len(keys))
	}

	now := time.Now().UTC()

	s.SetPortState("1.2.3.4:80", &state.PortState{
		Open: true, Hostnames: []string{"a.example.com"}, LastChecked: now,
	})

	s.SetPortState("1.2.3.4:443", &state.PortState{
		Open: true, Hostnames: []string{"a.example.com"}, LastChecked: now,
	})

	s.SetPortState("5.6.7.8:80", &state.PortState{
		Open: false, Hostnames: []string{"b.example.com"}, LastChecked: now,
	})

	keys = s.GetAllPortKeys()
	if len(keys) != 3 {
		t.Fatalf("expected 3 keys, got %d", len(keys))
	}

	keySet := make(map[string]bool)
	for _, k := range keys {
		keySet[k] = true
	}

	for _, want := range []string{"1.2.3.4:80", "1.2.3.4:443", "5.6.7.8:80"} {
		if !keySet[want] {
			t.Errorf("missing key %q", want)
		}
	}
}

// TestCertificateState_GetSet tests certificate state getter and setter.
func TestCertificateState_GetSet(t *testing.T) {
	t.Parallel()

	s := state.NewForTest()

	_, ok := s.GetCertificateState("1.2.3.4:443:www.example.com")
	if ok {
		t.Error("expected false for missing certificate")
	}

	now := time.Now().UTC().Truncate(time.Second)
	cs := &state.CertificateState{
		CommonName:              testHostname,
		Issuer:                  "Let's Encrypt Authority X3",
		NotAfter:                now.Add(90 * 24 * time.Hour),
		SubjectAlternativeNames: []string{testHostname},
		Status:                  "ok",
		LastChecked:             now,
	}

	s.SetCertificateState("1.2.3.4:443:www.example.com", cs)

	got, ok := s.GetCertificateState("1.2.3.4:443:www.example.com")
	if !ok {
		t.Fatal("expected true for existing certificate")
	}

	if got.CommonName != testHostname {
		t.Errorf("CN: got %q", got.CommonName)
	}

	if got.Issuer != "Let's Encrypt Authority X3" {
		t.Errorf("issuer: got %q", got.Issuer)
	}

	if got.Status != "ok" {
		t.Errorf("status: got %q", got.Status)
	}

	if len(got.SubjectAlternativeNames) != 1 {
		t.Errorf("SANs: expected 1, got %d", len(got.SubjectAlternativeNames))
	}
}

// TestCertificateState_ErrorField tests that the error field round-trips.
func TestCertificateState_ErrorField(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()
	s := state.NewForTestWithDataDir(dir)

	now := time.Now().UTC().Truncate(time.Second)
	cs := &state.CertificateState{
		Status:      "error",
		Error:       "connection refused",
		LastChecked: now,
	}

	s.SetCertificateState("10.0.0.1:443:err.example.com", cs)

	err := s.Save()
	if err != nil {
		t.Fatalf("Save() error: %v", err)
	}

	loaded := state.NewForTestWithDataDir(dir)

	err = loaded.Load()
	if err != nil {
		t.Fatalf("Load() error: %v", err)
	}

	got, ok := loaded.GetCertificateState("10.0.0.1:443:err.example.com")
	if !ok {
		t.Fatal("missing certificate after load")
	}

	if got.Status != "error" {
		t.Errorf("status: got %q, want %q", got.Status, "error")
	}

	if got.Error != "connection refused" {
		t.Errorf("error field: got %q", got.Error)
	}
}

// TestHostnameState_ErrorField tests that hostname error states round-trip.
func TestHostnameState_ErrorField(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()
	s := state.NewForTestWithDataDir(dir)

	now := time.Now().UTC().Truncate(time.Second)
	hs := &state.HostnameState{
		RecordsByNameserver: map[string]*state.NameserverRecordState{
			"ns1.example.com.": {
				Records:     nil,
				Status:      "error",
				Error:       "SERVFAIL",
				LastChecked: now,
			},
		},
		LastChecked: now,
	}

	s.SetHostnameState("fail.example.com", hs)

	err := s.Save()
	if err != nil {
		t.Fatalf("Save() error: %v", err)
	}

	loaded := state.NewForTestWithDataDir(dir)

	err = loaded.Load()
	if err != nil {
		t.Fatalf("Load() error: %v", err)
	}

	got, ok := loaded.GetHostnameState("fail.example.com")
	if !ok {
		t.Fatal("missing hostname after load")
	}

	nsState := got.RecordsByNameserver["ns1.example.com."]
	if nsState.Status != "error" {
		t.Errorf("status: got %q, want %q", nsState.Status, "error")
	}

	if nsState.Error != "SERVFAIL" {
		t.Errorf("error: got %q, want %q", nsState.Error, "SERVFAIL")
	}
}

// TestSnapshotVersion verifies that the snapshot version is written correctly.
func TestSnapshotVersion(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()
	s := state.NewForTestWithDataDir(dir)

	err := s.Save()
	if err != nil {
		t.Fatalf("Save() error: %v", err)
	}

	//nolint:gosec // test file with known path
	data, err := os.ReadFile(filepath.Join(dir, "state.json"))
	if err != nil {
		t.Fatalf("reading state file: %v", err)
	}

	var snap state.Snapshot

	err = json.Unmarshal(data, &snap)
	if err != nil {
		t.Fatalf("parsing state: %v", err)
	}

	if snap.Version != 1 {
		t.Errorf("version: got %d, want 1", snap.Version)
	}

	if snap.LastUpdated.IsZero() {
		t.Error("lastUpdated should be set after save")
	}
}

// TestSaveUpdatesLastUpdated verifies that Save sets LastUpdated.
func TestSaveUpdatesLastUpdated(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()
	s := state.NewForTestWithDataDir(dir)

	before := time.Now().UTC().Add(-time.Second)

	err := s.Save()
	if err != nil {
		t.Fatalf("Save() error: %v", err)
	}

	after := time.Now().UTC().Add(time.Second)

	snap := s.GetSnapshot()
	if snap.LastUpdated.Before(before) || snap.LastUpdated.After(after) {
		t.Errorf(
			"LastUpdated %v not in expected range [%v, %v]",
			snap.LastUpdated, before, after,
		)
	}
}

// TestLoadPreservesExistingStateOnMissingFile verifies that when Load is
// called and the file doesn't exist, the existing in-memory state is kept.
func TestLoadPreservesExistingStateOnMissingFile(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()
	s := state.NewForTestWithDataDir(dir)

	// Add some data before loading.
	s.SetDomainState("pre.example.com", &state.DomainState{
		Nameservers: []string{"ns1.pre.example.com."},
		LastChecked: time.Now().UTC(),
	})

	err := s.Load()
	if err != nil {
		t.Fatalf("Load() error: %v", err)
	}

	// Since the file doesn't exist, the existing data should persist.
	_, ok := s.GetDomainState("pre.example.com")
	if !ok {
		t.Error("existing domain state should persist when file is missing")
	}
}

// TestConcurrentGetSet verifies that concurrent reads and writes don't race.
func TestConcurrentGetSet(t *testing.T) {
	t.Parallel()

	s := state.NewForTest()

	const goroutines = 20

	var wg sync.WaitGroup

	wg.Add(goroutines)

	for i := range goroutines {
		go func(id int) {
			defer wg.Done()

			now := time.Now().UTC()
			key := string(rune('a' + id%26))

			runConcurrentOps(s, key, now)
		}(i)
	}

	wg.Wait()
}

// runConcurrentOps performs a series of get/set/delete operations for concurrency testing.
func runConcurrentOps(s *state.State, key string, now time.Time) {
	const iterations = 50

	for j := range iterations {
		s.SetDomainState(key+".com", &state.DomainState{
			Nameservers: []string{"ns1." + key + ".com."},
			LastChecked: now,
		})

		s.GetDomainState(key + ".com")

		s.SetPortState(key+":80", &state.PortState{
			Open: j%2 == 0, Hostnames: []string{key + ".com"}, LastChecked: now,
		})

		s.GetPortState(key + ":80")
		s.GetAllPortKeys()
		s.GetSnapshot()

		s.SetHostnameState(key+".example.com", &state.HostnameState{
			RecordsByNameserver: map[string]*state.NameserverRecordState{
				"ns1.test.": {
					Records:     map[string][]string{"A": {"1.2.3.4"}},
					Status:      "ok",
					LastChecked: now,
				},
			},
			LastChecked: now,
		})

		s.GetHostnameState(key + ".example.com")

		s.SetCertificateState("1.2.3.4:443:"+key+".com", &state.CertificateState{
			CommonName: key + ".com", Status: "ok", LastChecked: now,
		})

		s.GetCertificateState("1.2.3.4:443:" + key + ".com")

		if j%10 == 0 {
			s.DeletePortState(key + ":80")
		}
	}
}

// TestConcurrentSaveLoad verifies that concurrent Save and Load
// operations don't race or corrupt state.
func TestConcurrentSaveLoad(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()
	s := state.NewForTestWithDataDir(dir)

	populateState(t, s)

	const goroutines = 10

	var wg sync.WaitGroup

	wg.Add(goroutines)

	for i := range goroutines {
		go func(id int) {
			defer wg.Done()

			if id%2 == 0 {
				_ = s.Save()
			} else {
				_ = s.Load()
			}
		}(i)
	}

	wg.Wait()
}

// TestPortStateRoundTripThroughSaveLoad verifies backward-compat deserialization
// works through the full Save→Load cycle with old-format data on disk.
func TestPortStateRoundTripThroughSaveLoad(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()

	// Write a state file with old single-hostname port format.
	oldFormatJSON := `{
		"version": 1,
		"lastUpdated": "2026-02-19T12:00:00Z",
		"domains": {},
		"hostnames": {},
		"ports": {
			"10.0.0.1:80": {
				"open": true,
				"hostname": "legacy.example.com",
				"lastChecked": "2026-02-19T12:00:00Z"
			},
			"10.0.0.1:443": {
				"open": true,
				"hostnames": ["modern.example.com"],
				"lastChecked": "2026-02-19T12:00:00Z"
			}
		},
		"certificates": {}
	}`

	err := os.WriteFile(filepath.Join(dir, "state.json"), []byte(oldFormatJSON), 0o600)
	if err != nil {
		t.Fatalf("writing old format state: %v", err)
	}

	s := state.NewForTestWithDataDir(dir)

	err = s.Load()
	if err != nil {
		t.Fatalf("Load() error: %v", err)
	}

	// Verify old format was migrated.
	ps80, ok := s.GetPortState("10.0.0.1:80")
	if !ok {
		t.Fatal("missing port 10.0.0.1:80")
	}

	if len(ps80.Hostnames) != 1 || ps80.Hostnames[0] != "legacy.example.com" {
		t.Errorf("old format port hostnames: got %v", ps80.Hostnames)
	}

	// Verify new format loaded correctly.
	ps443, ok := s.GetPortState("10.0.0.1:443")
	if !ok {
		t.Fatal("missing port 10.0.0.1:443")
	}

	if len(ps443.Hostnames) != 1 || ps443.Hostnames[0] != "modern.example.com" {
		t.Errorf("new format port hostnames: got %v", ps443.Hostnames)
	}
}

// TestMultipleSavesOverwrite verifies that subsequent saves overwrite the
// previous state completely.
func TestMultipleSavesOverwrite(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()
	s := state.NewForTestWithDataDir(dir)

	s.SetDomainState("first.com", &state.DomainState{
		Nameservers: []string{"ns1.first.com."},
		LastChecked: time.Now().UTC(),
	})

	err := s.Save()
	if err != nil {
		t.Fatalf("first Save() error: %v", err)
	}

	// Create a brand new state with the same dir and set different data.
	s2 := state.NewForTestWithDataDir(dir)

	s2.SetDomainState("second.com", &state.DomainState{
		Nameservers: []string{"ns1.second.com."},
		LastChecked: time.Now().UTC(),
	})

	err = s2.Save()
	if err != nil {
		t.Fatalf("second Save() error: %v", err)
	}

	// Load and verify only the second domain exists.
	loaded := state.NewForTestWithDataDir(dir)

	err = loaded.Load()
	if err != nil {
		t.Fatalf("Load() error: %v", err)
	}

	snap := loaded.GetSnapshot()

	if _, ok := snap.Domains["first.com"]; ok {
		t.Error("first.com should not exist after overwrite")
	}

	if _, ok := snap.Domains["second.com"]; !ok {
		t.Error("second.com should exist after overwrite")
	}
}

// TestNewForTest verifies the test helper creates a valid empty state.
func TestNewForTest(t *testing.T) {
	t.Parallel()

	s := state.NewForTest()

	snap := s.GetSnapshot()

	if snap.Version != 1 {
		t.Errorf("version: got %d, want 1", snap.Version)
	}

	if snap.Domains == nil {
		t.Error("Domains map should be initialized")
	}

	if snap.Hostnames == nil {
		t.Error("Hostnames map should be initialized")
	}

	if snap.Ports == nil {
		t.Error("Ports map should be initialized")
	}

	if snap.Certificates == nil {
		t.Error("Certificates map should be initialized")
	}
}

// TestSaveFilePermissions verifies the saved file has restricted permissions.
func TestSaveFilePermissions(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()
	s := state.NewForTestWithDataDir(dir)

	err := s.Save()
	if err != nil {
		t.Fatalf("Save() error: %v", err)
	}

	info, err := os.Stat(filepath.Join(dir, "state.json"))
	if err != nil {
		t.Fatalf("stat error: %v", err)
	}

	perm := info.Mode().Perm()
	if perm != 0o600 {
		t.Errorf("file permissions: got %o, want 600", perm)
	}
}