package tlsparse

import (
	"net"
	"testing"
	"time"

	"ja4sentinel/api"

	tlsfingerprint "github.com/psanford/tlsfingerprint"
	"github.com/google/gopacket"
	"github.com/google/gopacket/layers"
)

func TestIsClientHello(t *testing.T) {
	tests := []struct {
		name    string
		payload []byte
		want    bool
	}{
		{
			name:    "empty payload",
			payload: []byte{},
			want:    false,
		},
		{
			name:    "too short",
			payload: []byte{0x16, 0x03, 0x03},
			want:    false,
		},
		{
			name:    "valid TLS 1.2 ClientHello",
			payload: createTLSClientHello(0x0303),
			want:    true,
		},
		{
			name:    "valid TLS 1.3 ClientHello",
			payload: createTLSClientHello(0x0304),
			want:    true,
		},
		{
			name:    "not a handshake",
			payload: []byte{0x17, 0x03, 0x03, 0x00, 0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
			want:    false,
		},
		{
			name:    "ServerHello (type 2)",
			payload: createTLSServerHello(0x0303),
			want:    false,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got := IsClientHello(tt.payload)
			if got != tt.want {
				t.Errorf("IsClientHello() = %v, want %v", got, tt.want)
			}
		})
	}
}

func TestParseClientHello(t *testing.T) {
	tests := []struct {
		name    string
		payload []byte
		wantErr bool
		wantNil bool
	}{
		{
			name:    "empty payload",
			payload: []byte{},
			wantErr: false,
			wantNil: true,
		},
		{
			name:    "valid ClientHello",
			payload: createTLSClientHello(0x0303),
			wantErr: false,
			wantNil: false,
		},
		{
			name:    "incomplete record",
			payload: []byte{0x16, 0x03, 0x03, 0x01, 0x00, 0x01},
			wantErr: false,
			wantNil: true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got, err := parseClientHello(tt.payload)
			if (err != nil) != tt.wantErr {
				t.Errorf("parseClientHello() error = %v, wantErr %v", err, tt.wantErr)
				return
			}
			if (got == nil) != tt.wantNil {
				t.Errorf("parseClientHello() = %v, wantNil %v", got == nil, tt.wantNil)
			}
		})
	}
}

func TestExtractIPMeta(t *testing.T) {
	ipLayer := &layers.IPv4{
		TTL:    64,
		Length: 1500,
		Id:     12345,
		Flags:  layers.IPv4DontFragment,
		SrcIP:  []byte{192, 168, 1, 1},
		DstIP:  []byte{10, 0, 0, 1},
	}

	meta := extractIPMeta(ipLayer)

	if meta.TTL != 64 {
		t.Errorf("TTL = %v, want 64", meta.TTL)
	}
	if meta.TotalLength != 1500 {
		t.Errorf("TotalLength = %v, want 1500", meta.TotalLength)
	}
	if meta.IPID != 12345 {
		t.Errorf("IPID = %v, want 12345", meta.IPID)
	}
	if !meta.DF {
		t.Error("DF = false, want true")
	}
}

func TestExtractTCPMeta(t *testing.T) {
	tcp := &layers.TCP{
		SrcPort: 12345,
		DstPort: 443,
		Window:  65535,
		Options: []layers.TCPOption{
			{
				OptionType: layers.TCPOptionKindMSS,
				OptionData: []byte{0x05, 0xb4}, // 1460
			},
			{
				OptionType: layers.TCPOptionKindWindowScale,
				OptionData: []byte{0x07}, // scale 7
			},
			{
				OptionType: layers.TCPOptionKindSACKPermitted,
				OptionData: []byte{},
			},
		},
	}

	meta := extractTCPMeta(tcp)

	if meta.WindowSize != 65535 {
		t.Errorf("WindowSize = %v, want 65535", meta.WindowSize)
	}
	if meta.MSS != 1460 {
		t.Errorf("MSS = %v, want 1460", meta.MSS)
	}
	if meta.WindowScale != 7 {
		t.Errorf("WindowScale = %v, want 7", meta.WindowScale)
	}
	if len(meta.Options) != 3 {
		t.Errorf("Options length = %v, want 3", len(meta.Options))
	}
}

// Helper functions to create test TLS records

func createTLSClientHello(version uint16) []byte {
	// Minimal TLS ClientHello record
	handshake := []byte{
		0x01,                   // Handshake type: ClientHello
		0x00, 0x00, 0x00, 0x10, // Handshake length (16 bytes)
		// ClientHello body (simplified)
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	}

	record := make([]byte, 5+len(handshake))
	record[0] = 0x16 // Handshake
	record[1] = byte(version >> 8)
	record[2] = byte(version)
	record[3] = byte(len(handshake) >> 8)
	record[4] = byte(len(handshake))
	copy(record[5:], handshake)

	return record
}

func createTLSServerHello(version uint16) []byte {
	// Minimal TLS ServerHello record
	handshake := []byte{
		0x02,                   // Handshake type: ServerHello
		0x00, 0x00, 0x00, 0x10, // Handshake length
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
	}

	record := make([]byte, 5+len(handshake))
	record[0] = 0x16 // Handshake
	record[1] = byte(version >> 8)
	record[2] = byte(version)
	record[3] = byte(len(handshake) >> 8)
	record[4] = byte(len(handshake))
	copy(record[5:], handshake)

	return record
}

func TestNewParser(t *testing.T) {
	parser := NewParser()
	defer parser.Close()

	if parser == nil {
		t.Error("NewParser() returned nil")
	}
	if parser.flows == nil {
		t.Error("NewParser() flows map not initialized")
	}
	if parser.flowTimeout == 0 {
		t.Error("NewParser() flowTimeout not set")
	}
}

func TestParserClose(t *testing.T) {
	parser := NewParser()
	err := parser.Close()
	if err != nil {
		t.Errorf("Close() error = %v", err)
	}
}

func TestFlowKey(t *testing.T) {
	// Test unidirectional flow key (client -> server only)
	key := flowKey("192.168.1.1", 12345, "10.0.0.1", 443)
	expected := "192.168.1.1:12345->10.0.0.1:443"
	if key != expected {
		t.Errorf("flowKey() = %v, want %v", key, expected)
	}
}

func TestParserConnectionStateTracking(t *testing.T) {
	parser := NewParser()
	defer parser.Close()

	// Create a valid ClientHello payload
	clientHello := createTLSClientHello(0x0303)

	// Test parseClientHello directly (lower-level test)
	result, err := parseClientHello(clientHello)
	if err != nil {
		t.Errorf("parseClientHello() error = %v", err)
	}
	if result == nil {
		t.Error("parseClientHello() should return ClientHello")
	}

	// Test IsClientHello helper
	if !IsClientHello(clientHello) {
		t.Error("IsClientHello() should return true for valid ClientHello")
	}
}

func TestParserClose_Idempotent(t *testing.T) {
	parser := NewParser()

	if err := parser.Close(); err != nil {
		t.Fatalf("first Close() error = %v", err)
	}
	if err := parser.Close(); err != nil {
		t.Fatalf("second Close() error = %v", err)
	}
}

func TestExtractTCPMeta_MSSInvalid_NoPanic(t *testing.T) {
	tcp := &layers.TCP{
		Window: 1234,
		Options: []layers.TCPOption{
			{
				OptionType: layers.TCPOptionKindMSS,
				OptionData: []byte{0x05}, // malformed (1 byte instead of 2)
			},
		},
	}

	meta := extractTCPMeta(tcp)

	found := false
	for _, opt := range meta.Options {
		if opt == "MSS_INVALID" {
			found = true
			break
		}
	}
	if !found {
		t.Fatalf("expected MSS_INVALID in options, got %v", meta.Options)
	}
}

func TestGetOrCreateFlow_RespectsMaxTrackedFlows(t *testing.T) {
	parser := NewParser()
	defer parser.Close()

	parser.maxTrackedFlows = 1

	flow1 := parser.getOrCreateFlow(
		flowKey("192.168.1.1", 12345, "10.0.0.1", 443),
		"192.168.1.1", 12345, "10.0.0.1", 443,
		api.IPMeta{}, api.TCPMeta{},
	)
	if flow1 == nil {
		t.Fatal("first flow should be created")
	}

	flow2 := parser.getOrCreateFlow(
		flowKey("192.168.1.2", 12346, "10.0.0.1", 443),
		"192.168.1.2", 12346, "10.0.0.1", 443,
		api.IPMeta{}, api.TCPMeta{},
	)
	if flow2 != nil {
		t.Fatal("second flow should be nil when maxTrackedFlows is reached")
	}
}

func TestProcess_DropsWhenHelloBufferExceedsLimit(t *testing.T) {
	parser := NewParserWithTimeout(30 * time.Second)
	defer parser.Close()

	parser.maxHelloBufferBytes = 10

	srcIP := "192.168.1.10"
	dstIP := "10.0.0.1"
	srcPort := uint16(12345)
	dstPort := uint16(443)

	// TLS-like payload, but intentionally incomplete to trigger accumulation.
	payloadChunk := []byte{0x16, 0x03, 0x03, 0x00, 0x20, 0x01} // len = 6

	pkt1 := buildRawPacketWithSeq(t, srcIP, dstIP, srcPort, dstPort, payloadChunk, 1)
	ch, err := parser.Process(pkt1)
	if err != nil {
		t.Fatalf("first Process() error = %v", err)
	}
	if ch != nil {
		t.Fatal("first Process() should not return complete ClientHello")
	}

	key := flowKey(srcIP, srcPort, dstIP, dstPort)

	parser.mu.RLock()
	_, existsAfterFirst := parser.flows[key]
	parser.mu.RUnlock()
	if !existsAfterFirst {
		t.Fatal("flow should exist after first chunk")
	}

	pkt2 := buildRawPacketWithSeq(t, srcIP, dstIP, srcPort, dstPort, payloadChunk, 1+uint32(len(payloadChunk)))
	ch, err = parser.Process(pkt2)
	if err != nil {
		t.Fatalf("second Process() error = %v", err)
	}
	if ch != nil {
		t.Fatal("second Process() should not return ClientHello")
	}

	parser.mu.RLock()
	_, existsAfterSecond := parser.flows[key]
	parser.mu.RUnlock()
	if existsAfterSecond {
		t.Fatal("flow should be removed when hello buffer exceeds maxHelloBufferBytes")
	}
}

func TestProcess_NonTLSNewFlowNotTracked(t *testing.T) {
	parser := NewParser()
	defer parser.Close()

	srcIP := "192.168.1.20"
	dstIP := "10.0.0.2"
	srcPort := uint16(23456)
	dstPort := uint16(443)

	// Non-TLS content type (not 22)
	payload := []byte{0x17, 0x03, 0x03, 0x00, 0x05, 0x00}

	pkt := buildRawPacket(t, srcIP, dstIP, srcPort, dstPort, payload)
	ch, err := parser.Process(pkt)
	if err != nil {
		t.Fatalf("Process() error = %v", err)
	}
	if ch != nil {
		t.Fatal("Process() should return nil for non-TLS new flow")
	}

	key := flowKey(srcIP, srcPort, dstIP, dstPort)

	parser.mu.RLock()
	_, exists := parser.flows[key]
	parser.mu.RUnlock()
	if exists {
		t.Fatal("non-TLS new flow should not be tracked")
	}
}

func buildRawPacket(t *testing.T, srcIP, dstIP string, srcPort, dstPort uint16, payload []byte) api.RawPacket {
	return buildRawPacketWithSeq(t, srcIP, dstIP, srcPort, dstPort, payload, 1)
}

func buildRawPacketWithSeq(t *testing.T, srcIP, dstIP string, srcPort, dstPort uint16, payload []byte, seq uint32) api.RawPacket {
	t.Helper()

	ip := &layers.IPv4{
		Version:  4,
		TTL:      64,
		SrcIP:    net.ParseIP(srcIP).To4(),
		DstIP:    net.ParseIP(dstIP).To4(),
		Protocol: layers.IPProtocolTCP,
	}

	tcp := &layers.TCP{
		SrcPort: layers.TCPPort(srcPort),
		DstPort: layers.TCPPort(dstPort),
		Seq:     seq,
		ACK:     true,
		Window:  65535,
	}
	if err := tcp.SetNetworkLayerForChecksum(ip); err != nil {
		t.Fatalf("SetNetworkLayerForChecksum() error = %v", err)
	}

	eth := &layers.Ethernet{
		SrcMAC:       net.HardwareAddr{0x00, 0x11, 0x22, 0x33, 0x44, 0x55},
		DstMAC:       net.HardwareAddr{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff},
		EthernetType: layers.EthernetTypeIPv4,
	}

	buf := gopacket.NewSerializeBuffer()
	opts := gopacket.SerializeOptions{
		FixLengths:       true,
		ComputeChecksums: true,
	}

	if err := gopacket.SerializeLayers(buf, opts, eth, ip, tcp, gopacket.Payload(payload)); err != nil {
		t.Fatalf("SerializeLayers() error = %v", err)
	}

	return api.RawPacket{
		Data:      buf.Bytes(),
		Timestamp: time.Now().UnixNano(),
		LinkType:  1, // Ethernet
	}
}

func TestTLSVersionToString(t *testing.T) {
	tests := []struct {
		version uint16
		want    string
	}{
		{0x0301, "1.0"},
		{0x0302, "1.1"},
		{0x0303, "1.2"},
		{0x0304, "1.3"},
		{0x0300, ""},
		{0x0305, ""},
	}

	for _, tt := range tests {
		t.Run(tt.want, func(t *testing.T) {
			got := tlsVersionToString(tt.version)
			if got != tt.want {
				t.Errorf("tlsVersionToString(%#x) = %v, want %v", tt.version, got, tt.want)
			}
		})
	}
}

func TestExtractTLSExtensions(t *testing.T) {
	tests := []struct {
		name        string
		payload     []byte
		wantSNI     string
		wantALPN    []string
		wantVersion string
		wantNil     bool
	}{
		{
			name:    "empty payload",
			payload: []byte{},
			wantNil: true,
		},
		{
			name:    "too short",
			payload: []byte{0x16, 0x03, 0x03},
			wantNil: true,
		},
		{
			name:        "TLS 1.2 ClientHello without extensions",
			payload:     createTLSClientHello(0x0303),
			wantVersion: "1.2",
			wantNil:     false,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got, _ := extractTLSExtensions(tt.payload)
			// For empty/too short payloads, nil is acceptable
			// For valid ClientHellos, got should contain at least partial info
			if !tt.wantNil && got == nil {
				t.Errorf("extractTLSExtensions() = %v, want non-nil with partial info", got)
				return
			}
			if got != nil {
				if got.TLSVersion != tt.wantVersion && tt.wantVersion != "" {
					t.Errorf("TLSVersion = %v, want %v", got.TLSVersion, tt.wantVersion)
				}
			}
		})
	}
}

func TestParser_ExtractsTLSFields(t *testing.T) {
	parser := NewParser()
	defer parser.Close()

	// Create a minimal valid TLS 1.2 ClientHello with SNI and ALPN extensions
	// This is a real-world-like ClientHello structure
	clientHelloWithExt := createMinimalTLSClientHelloWithSNIAndALPN("example.com", []string{"h2", "http/1.1"})

	// Debug: Check what extractTLSExtensions returns
	extInfo, err := extractTLSExtensions(clientHelloWithExt)
	if err != nil {
		t.Logf("extractTLSExtensions error: %v", err)
	}
	if extInfo != nil {
		t.Logf("extInfo: SNI=%q, ALPN=%v, Version=%q", extInfo.SNI, extInfo.ALPN, extInfo.TLSVersion)
	} else {
		t.Log("extInfo is nil")
	}

	// Also test with tlsfingerprint directly
	fp, err := tlsfingerprint.ParseClientHello(clientHelloWithExt)
	if err != nil {
		t.Logf("tlsfingerprint error: %v", err)
	} else {
		t.Logf("tlsfingerprint: ALPN=%v, Version=%#x, HasSNI=%v", fp.ALPNProtocols, fp.Version, fp.HasSNI)
	}

	// Debug: print first bytes of ClientHello
	t.Logf("ClientHello hex: % x", clientHelloWithExt[:min(50, len(clientHelloWithExt))])

	srcIP := "192.168.1.100"
	dstIP := "10.0.0.1"
	srcPort := uint16(54321)
	dstPort := uint16(443)

	pkt := buildRawPacket(t, srcIP, dstIP, srcPort, dstPort, clientHelloWithExt)

	result, err := parser.Process(pkt)
	if err != nil {
		t.Fatalf("Process() error = %v", err)
	}
	if result == nil {
		t.Fatal("Process() should return TLSClientHello")
	}

	// Verify new fields are populated
	if result.SNI != "example.com" {
		t.Errorf("SNI = %v, want example.com", result.SNI)
	}
	if result.ALPN == "" {
		t.Error("ALPN should not be empty")
	}
	if result.TLSVersion != "1.2" {
		t.Errorf("TLSVersion = %v, want 1.2", result.TLSVersion)
	}
	if result.ConnID == "" {
		t.Error("ConnID should not be empty")
	}
	if result.SynToCHMs == nil {
		t.Error("SynToCHMs should not be nil")
	}
}

// createMinimalTLSClientHelloWithSNIAndALPN creates a minimal but valid TLS 1.2 ClientHello
// with SNI and ALPN extensions
func createMinimalTLSClientHelloWithSNIAndALPN(sni string, alpnProtocols []string) []byte {
	// Build SNI extension
	sniExt := buildSNIExtension(sni)

	// Build ALPN extension
	alpnExt := buildALPNExtension(alpnProtocols)

	// Build supported_versions extension (TLS 1.2)
	supportedVersionsExt := []byte{0x00, 0x2b, 0x00, 0x03, 0x02, 0x03, 0x03} // type=43, len=3, TLS 1.2

	// Combine extensions
	extensions := append(sniExt, alpnExt...)
	extensions = append(extensions, supportedVersionsExt...)
	extLen := len(extensions)

	// Cipher suites (minimal set)
	cipherSuites := []byte{0x00, 0x04, 0x13, 0x01, 0x13, 0x02, 0xc0, 0x2f}
	// 4 cipher suites: TLS_AES_128_GCM_SHA256, TLS_AES_256_GCM_SHA384, TLS_CHACHA20_POLY1305_SHA256, TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256

	// Compression methods (null only)
	compressionMethods := []byte{0x01, 0x00}

	// Build ClientHello handshake (without length header first)
	handshakeBody := []byte{
		0x03, 0x03,             // Version: TLS 1.2
		// Random (32 bytes)
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		0x00,                   // Session ID length: 0
	}

	// Add cipher suites (with length prefix)
	cipherSuiteLen := len(cipherSuites)
	handshakeBody = append(handshakeBody, byte(cipherSuiteLen>>8), byte(cipherSuiteLen))
	handshakeBody = append(handshakeBody, cipherSuites...)

	// Add compression methods (with length prefix)
	handshakeBody = append(handshakeBody, compressionMethods...)

	// Add extensions (with length prefix)
	handshakeBody = append(handshakeBody, byte(extLen>>8), byte(extLen))
	handshakeBody = append(handshakeBody, extensions...)

	// Now build full handshake with type and length
	handshakeLen := len(handshakeBody)
	handshake := append([]byte{
		0x01,                   // Handshake type: ClientHello
		byte(handshakeLen >> 16), byte(handshakeLen >> 8), byte(handshakeLen), // Handshake length
	}, handshakeBody...)

	// Build TLS record
	recordLen := len(handshake)
	record := make([]byte, 5+recordLen)
	record[0] = 0x16 // Handshake
	record[1] = 0x03 // Version: TLS 1.2
	record[2] = 0x03
	record[3] = byte(recordLen >> 8)
	record[4] = byte(recordLen)
	copy(record[5:], handshake)

	return record
}

// buildSNIExtension builds a Server Name Indication extension
func buildSNIExtension(sni string) []byte {
	nameLen := len(sni)
	// SNI extension structure:
	// - name_list_len (2 bytes): total length of all names
	// - name_type (1 byte): always 0x00 for host_name
	// - name_len (2 bytes): length of this name
	// - name (variable): the actual hostname
	nameListLen := 1 + 2 + nameLen // name_type + name_len + name
	
	// Extension data = name_list_len (2) + name_type (1) + name_len (2) + name
	extDataLen := 2 + nameListLen
	// Full extension = type (2) + length (2) + data (variable)
	ext := make([]byte, 4+extDataLen)
	ext[0] = 0x00 // Extension type: SNI (0)
	ext[1] = 0x00
	ext[2] = byte(extDataLen >> 8)
	ext[3] = byte(extDataLen)
	ext[4] = byte(nameListLen >> 8)  // name_list_len (high byte)
	ext[5] = byte(nameListLen)       // name_list_len (low byte)
	ext[6] = 0x00                    // name_type: host_name (0)
	ext[7] = byte(nameLen >> 8)      // name_len (high byte)
	ext[8] = byte(nameLen)           // name_len (low byte)
	copy(ext[9:], sni)

	return ext
}

// buildALPNExtension builds an Application-Layer Protocol Negotiation extension
func buildALPNExtension(protocols []string) []byte {
	// Calculate ALPN data length
	// ALPN data = alpn_list_len (2) + for each protocol: length (1) + data (variable)
	alpnDataLen := 0
	for _, proto := range protocols {
		alpnDataLen += 1 + len(proto) // length byte + protocol string
	}

	// Extension data = alpn_list_len (2) + protocols
	extDataLen := 2 + alpnDataLen
	// Full extension = type (2) + length (2) + data (variable)
	ext := make([]byte, 4+extDataLen)
	ext[0] = 0x00 // Extension type: ALPN (16 = 0x10)
	ext[1] = 0x10
	ext[2] = byte(extDataLen >> 8)
	ext[3] = byte(extDataLen)

	// ALPN protocol list length (2 bytes)
	ext[4] = byte(alpnDataLen >> 8)
	ext[5] = byte(alpnDataLen)

	offset := 6
	for _, proto := range protocols {
		ext[offset] = byte(len(proto))
		offset++
		copy(ext[offset:], proto)
		offset += len(proto)
	}

	return ext
}

// min returns the minimum of two integers
func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

// TestExtractSNIFromPayload tests the SNI extraction function
func TestExtractSNIFromPayload(t *testing.T) {
	tests := []struct {
		name     string
		payload  []byte
		wantSNI  string
	}{
		{
			name:     "empty_payload",
			payload:  []byte{},
			wantSNI:  "",
		},
		{
			name:     "payload_too_short",
			payload:  []byte{0x01, 0x00, 0x00, 0x10}, // Only 4 bytes
			wantSNI:  "",
		},
		{
			name:     "no_extensions",
			payload:  buildClientHelloWithoutExtensions(),
			wantSNI:  "",
		},
		{
			name:     "with_sni_extension",
			payload:  buildClientHelloWithSNI("example.com"),
			wantSNI:  "example.com",
		},
		{
			name:     "with_sni_long_domain",
			payload:  buildClientHelloWithSNI("very-long-subdomain.example-test-domain.com"),
			wantSNI:  "very-long-subdomain.example-test-domain.com",
		},
		{
			name:     "malformed_sni_truncated",
			payload:  buildTruncatedSNI(),
			wantSNI:  "",
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got := extractSNIFromPayload(tt.payload)
			if got != tt.wantSNI {
				t.Errorf("extractSNIFromPayload() = %q, want %q", got, tt.wantSNI)
			}
		})
	}
}

// TestCleanupExpiredFlows tests the flow cleanup functionality
func TestCleanupExpiredFlows(t *testing.T) {
	p := NewParser()
	if p == nil {
		t.Fatal("NewParser() returned nil")
	}
	defer p.Close()

	// Create a flow manually using exported types
	key := "192.168.1.1:12345->10.0.0.1:443"
	flow := &ConnectionFlow{
		State:       NEW,
		LastSeen:    time.Now().Add(-2 * time.Hour), // Old flow
		HelloBuffer: make([]byte, 0),
	}

	p.mu.Lock()
	p.flows[key] = flow
	p.mu.Unlock()

	// Call cleanup
	p.cleanupExpiredFlows()

	// Flow should be deleted
	p.mu.RLock()
	_, exists := p.flows[key]
	p.mu.RUnlock()

	if exists {
		t.Error("cleanupExpiredFlows() should have removed the expired flow")
	}
}

// TestCleanupExpiredFlows_JA4Done tests that JA4_DONE flows are cleaned up immediately
func TestCleanupExpiredFlows_JA4Done(t *testing.T) {
	p := NewParser()
	if p == nil {
		t.Fatal("NewParser() returned nil")
	}
	defer p.Close()

	// Create a JA4_DONE flow (should be cleaned up regardless of timestamp)
	key := "192.168.1.1:12345->10.0.0.1:443"
	flow := &ConnectionFlow{
		State:       JA4_DONE,
		LastSeen:    time.Now(), // Recent, but should still be deleted
		HelloBuffer: make([]byte, 0),
	}

	p.mu.Lock()
	p.flows[key] = flow
	p.mu.Unlock()

	// Call cleanup
	p.cleanupExpiredFlows()

	// Flow should be deleted
	p.mu.RLock()
	_, exists := p.flows[key]
	p.mu.RUnlock()

	if exists {
		t.Error("cleanupExpiredFlows() should have removed the JA4_DONE flow")
	}
}

// TestCleanupExpiredFlows_RecentFlow tests that recent flows are NOT cleaned up
func TestCleanupExpiredFlows_RecentFlow(t *testing.T) {
	p := NewParser()
	if p == nil {
		t.Fatal("NewParser() returned nil")
	}
	defer p.Close()

	// Create a recent flow (should NOT be cleaned up)
	key := "192.168.1.1:12345->10.0.0.1:443"
	flow := &ConnectionFlow{
		State:       WAIT_CLIENT_HELLO,
		LastSeen:    time.Now(),
		HelloBuffer: make([]byte, 0),
	}

	p.mu.Lock()
	p.flows[key] = flow
	p.mu.Unlock()

	// Call cleanup
	p.cleanupExpiredFlows()

	// Flow should still exist
	p.mu.RLock()
	_, exists := p.flows[key]
	p.mu.RUnlock()

	if !exists {
		t.Error("cleanupExpiredFlows() should NOT have removed the recent flow")
	}
}

// TestCleanupLoop tests the cleanup goroutine shutdown
func TestCleanupLoop_Shutdown(t *testing.T) {
	p := NewParser()
	if p == nil {
		t.Fatal("NewParser() returned nil")
	}

	// Close should stop the cleanup loop
	err := p.Close()
	if err != nil {
		t.Errorf("Close() error = %v", err)
	}

	// Give goroutine time to exit
	time.Sleep(100 * time.Millisecond)

	// Verify cleanupDone channel is closed
	select {
	case _, ok := <-p.cleanupDone:
		if ok {
			t.Error("cleanupDone channel should be closed after Close()")
		}
	default:
		t.Error("cleanupDone channel should be closed after Close()")
	}
}

// buildClientHelloWithoutExtensions creates a ClientHello without extensions
func buildClientHelloWithoutExtensions() []byte {
	// Minimal ClientHello: type(1) + len(3) + version(2) + random(32) + sessionIDLen(1) + cipherLen(2) + compressLen(1) + extLen(2)
	handshake := make([]byte, 43)
	handshake[0] = 0x01 // ClientHello type
	handshake[1] = 0x00
	handshake[2] = 0x00
	handshake[3] = 0x27 // Length
	handshake[4] = 0x03 // Version TLS 1.2
	handshake[5] = 0x03
	// Random (32 bytes) - zeros
	handshake[38] = 0x00 // Session ID length
	handshake[39] = 0x00 // Cipher suite length (high)
	handshake[40] = 0x02 // Cipher suite length (low)
	handshake[41] = 0x13 // Cipher suite data
	handshake[42] = 0x01
	// Compression length (1 byte) - 0
	// Extensions length (2 bytes) - 0
	return handshake
}

// buildClientHelloWithSNI creates a ClientHello with SNI extension
func buildClientHelloWithSNI(sni string) []byte {
	// Build base handshake
	handshake := make([]byte, 43)
	handshake[0] = 0x01 // ClientHello type
	handshake[1] = 0x00
	handshake[2] = 0x00
	handshake[4] = 0x03 // Version TLS 1.2
	handshake[5] = 0x03
	handshake[38] = 0x00 // Session ID length
	handshake[39] = 0x00 // Cipher suite length (high)
	handshake[40] = 0x02 // Cipher suite length (low)
	handshake[41] = 0x13 // Cipher suite data
	handshake[42] = 0x01

	// Add compression length (1 byte) - 0
	handshake = append(handshake, 0x00)

	// Add extensions
	sniExt := buildSNIExtension(sni)
	extLen := len(sniExt)
	handshake = append(handshake, byte(extLen>>8), byte(extLen))
	handshake = append(handshake, sniExt...)

	// Update handshake length
	handshakeLen := len(handshake) - 4
	handshake[1] = byte(handshakeLen >> 16)
	handshake[2] = byte(handshakeLen >> 8)
	handshake[3] = byte(handshakeLen)

	return handshake
}

// buildTruncatedSNI creates a malformed ClientHello with truncated SNI
func buildTruncatedSNI() []byte {
	// Build base handshake
	handshake := make([]byte, 44)
	handshake[0] = 0x01
	handshake[4] = 0x03
	handshake[5] = 0x03
	handshake[38] = 0x00
	handshake[39] = 0x00
	handshake[40] = 0x02
	handshake[41] = 0x13
	handshake[42] = 0x01
	handshake[43] = 0x00 // Compression length

	// Add extensions with truncated SNI
	// Extension type (2) + length (2) + data (truncated)
	handshake = append(handshake, 0x00, 0x0a) // Extension length says 10 bytes
	handshake = append(handshake, 0x00, 0x05) // But only provide 5 bytes of data
	handshake = append(handshake, 0x00, 0x03, 0x74, 0x65, 0x73) // "tes" truncated

	return handshake
}

// TestJoinStringSlice tests the deprecated helper function
func TestJoinStringSlice(t *testing.T) {
	tests := []struct {
		name  string
		slice []string
		sep   string
		want  string
	}{
		{
			name:  "empty_slice",
			slice: []string{},
			sep:   ",",
			want:  "",
		},
		{
			name:  "single_element",
			slice: []string{"MSS"},
			sep:   ",",
			want:  "MSS",
		},
		{
			name:  "multiple_elements",
			slice: []string{"MSS", "SACK", "TS"},
			sep:   ",",
			want:  "MSS,SACK,TS",
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got := joinStringSlice(tt.slice, tt.sep)
			if got != tt.want {
				t.Errorf("joinStringSlice() = %q, want %q", got, tt.want)
			}
		})
	}
}

// TestProcess_NilPacketData tests error handling for nil packet data
func TestProcess_NilPacketData(t *testing.T) {
	p := NewParser()
	if p == nil {
		t.Fatal("NewParser() returned nil")
	}
	defer p.Close()

	pkt := api.RawPacket{
		Data:      nil,
		Timestamp: time.Now().UnixNano(),
	}

	_, err := p.Process(pkt)

	if err == nil {
		t.Error("Process() with nil data should return error")
	}
	if err.Error() != "empty packet data" {
		t.Errorf("Process() error = %v, want 'empty packet data'", err)
	}
}

// TestProcess_EmptyPacketData tests error handling for empty packet data
func TestProcess_EmptyPacketData(t *testing.T) {
	p := NewParser()
	if p == nil {
		t.Fatal("NewParser() returned nil")
	}
	defer p.Close()

	pkt := api.RawPacket{
		Data:      []byte{},
		Timestamp: time.Now().UnixNano(),
	}

	_, err := p.Process(pkt)

	if err == nil {
		t.Error("Process() with empty data should return error")
	}
}

// TestProcess_SLLPacket tests parsing of Linux SLL (cooked capture) packets
func TestProcess_SLLPacket(t *testing.T) {
	p := NewParser()
	if p == nil {
		t.Fatal("NewParser() returned nil")
	}
	defer p.Close()

	srcIP := "192.168.1.100"
	dstIP := "10.0.0.1"
	srcPort := uint16(54321)
	dstPort := uint16(443)

	// Create a valid ClientHello payload
	clientHello := createTLSClientHello(0x0303)

	// Build SLL packet instead of Ethernet
	pkt := buildSLLRawPacket(t, srcIP, dstIP, srcPort, dstPort, clientHello)

	// Debug: try to parse the packet manually
	packet := gopacket.NewPacket(pkt.Data, layers.LinkTypeLinuxSLL, gopacket.Default)
	ipLayer := packet.Layer(layers.LayerTypeIPv4)
	if ipLayer == nil {
		t.Logf("DEBUG: SLL packet - no IPv4 layer found")
		t.Logf("DEBUG: Packet data (first 50 bytes): % x", pkt.Data[:min(50, len(pkt.Data))])
		t.Logf("DEBUG: Packet layers: %v", packet.Layers())
	}

	result, err := p.Process(pkt)
	if err != nil {
		t.Fatalf("Process() with SLL packet error = %v", err)
	}
	if result == nil {
		t.Fatal("Process() with SLL packet should return TLSClientHello")
	}
	if result.SrcIP != srcIP {
		t.Errorf("SrcIP = %v, want %v", result.SrcIP, srcIP)
	}
	if result.DstIP != dstIP {
		t.Errorf("DstIP = %v, want %v", result.DstIP, dstIP)
	}
}

// TestProcess_SLLPacket_IPv6 tests parsing of Linux SLL IPv6 packets
func TestProcess_SLLPacket_IPv6(t *testing.T) {
	p := NewParser()
	if p == nil {
		t.Fatal("NewParser() returned nil")
	}
	defer p.Close()

	srcIP := "2001:db8::1"
	dstIP := "2001:db8::2"
	srcPort := uint16(54321)
	dstPort := uint16(443)

	// Create a valid ClientHello payload
	clientHello := createTLSClientHello(0x0303)

	// Build SLL IPv6 packet
	pkt := buildSLLRawPacketIPv6(t, srcIP, dstIP, srcPort, dstPort, clientHello)

	result, err := p.Process(pkt)
	if err != nil {
		t.Fatalf("Process() with SLL IPv6 packet error = %v", err)
	}
	if result == nil {
		t.Fatal("Process() with SLL IPv6 packet should return TLSClientHello")
	}
	if result.SrcIP != srcIP {
		t.Errorf("SrcIP = %v, want %v", result.SrcIP, srcIP)
	}
	if result.DstIP != dstIP {
		t.Errorf("DstIP = %v, want %v", result.DstIP, dstIP)
	}
}

// TestProcess_EthernetFallback tests that Ethernet parsing still works
func TestProcess_EthernetFallback(t *testing.T) {
	p := NewParser()
	if p == nil {
		t.Fatal("NewParser() returned nil")
	}
	defer p.Close()

	srcIP := "192.168.1.100"
	dstIP := "10.0.0.1"
	srcPort := uint16(54321)
	dstPort := uint16(443)

	clientHello := createTLSClientHello(0x0303)

	// Build standard Ethernet packet
	pkt := buildRawPacket(t, srcIP, dstIP, srcPort, dstPort, clientHello)

	result, err := p.Process(pkt)
	if err != nil {
		t.Fatalf("Process() with Ethernet packet error = %v", err)
	}
	if result == nil {
		t.Fatal("Process() with Ethernet packet should return TLSClientHello")
	}
}

// buildSLLRawPacket builds a Linux SLL (cooked capture) packet
// Manually constructs SLL header since layers.LinuxSLL doesn't implement SerializableLayer
func buildSLLRawPacket(t *testing.T, srcIP, dstIP string, srcPort, dstPort uint16, payload []byte) api.RawPacket {
	t.Helper()

	// Linux SLL header (16 bytes) - manually constructed
	// See: https://www.tcpdump.org/linktypes/LINKTYPE_LINUX_SLL.html
	// Packet type (2 bytes): 0x0000 = PACKET_HOST
	// Address length (2 bytes): 0x0006 = 6 bytes (MAC)
	// Address (8 bytes): 00:11:22:33:44:55 + 2 padding bytes
	// Protocol type (2 bytes): 0x0800 = IPv4
	sllHeader := make([]byte, 16)
	sllHeader[0] = 0x00 // Packet type: PACKET_HOST (high byte)
	sllHeader[1] = 0x00 // Packet type: PACKET_HOST (low byte)
	sllHeader[2] = 0x00 // Address length (high byte)
	sllHeader[3] = 0x06 // Address length (low byte) = 6
	// Address (8 bytes, only 6 used)
	sllHeader[4] = 0x00
	sllHeader[5] = 0x11
	sllHeader[6] = 0x22
	sllHeader[7] = 0x33
	sllHeader[8] = 0x44
	sllHeader[9] = 0x55
	sllHeader[10] = 0x00 // Padding
	sllHeader[11] = 0x00 // Padding
	sllHeader[12] = 0x08 // Protocol type: IPv4 (high byte)
	sllHeader[13] = 0x00 // Protocol type: IPv4 (low byte)

	ip := &layers.IPv4{
		Version:  4,
		TTL:      64,
		SrcIP:    net.ParseIP(srcIP).To4(),
		DstIP:    net.ParseIP(dstIP).To4(),
		Protocol: layers.IPProtocolTCP,
	}

	tcp := &layers.TCP{
		SrcPort: layers.TCPPort(srcPort),
		DstPort: layers.TCPPort(dstPort),
		Seq:     1,
		ACK:     true,
		Window:  65535,
	}
	if err := tcp.SetNetworkLayerForChecksum(ip); err != nil {
		t.Fatalf("SetNetworkLayerForChecksum() error = %v", err)
	}

	buf := gopacket.NewSerializeBuffer()
	opts := gopacket.SerializeOptions{
		FixLengths:       true,
		ComputeChecksums: true,
	}

	// Serialize IP + TCP + payload (SLL header is prepended manually)
	if err := gopacket.SerializeLayers(buf, opts, ip, tcp, gopacket.Payload(payload)); err != nil {
		t.Fatalf("SerializeLayers() error = %v", err)
	}

	// Prepend SLL header
	packetData := append(sllHeader, buf.Bytes()...)

	return api.RawPacket{
		Data:      packetData,
		Timestamp: time.Now().UnixNano(),
		LinkType:  101, // Linux SLL
	}
}

// buildSLLRawPacketIPv6 builds a Linux SLL IPv6 packet
func buildSLLRawPacketIPv6(t *testing.T, srcIP, dstIP string, srcPort, dstPort uint16, payload []byte) api.RawPacket {
	t.Helper()

	// Linux SLL header for IPv6
	// Protocol type: 0x86DD = IPv6
	sllHeader := make([]byte, 16)
	sllHeader[0] = 0x00 // Packet type: PACKET_HOST (high byte)
	sllHeader[1] = 0x00 // Packet type: PACKET_HOST (low byte)
	sllHeader[2] = 0x00 // Address length (high byte)
	sllHeader[3] = 0x06 // Address length (low byte) = 6
	// Address (8 bytes, only 6 used)
	sllHeader[4] = 0x00
	sllHeader[5] = 0x11
	sllHeader[6] = 0x22
	sllHeader[7] = 0x33
	sllHeader[8] = 0x44
	sllHeader[9] = 0x55
	sllHeader[10] = 0x00 // Padding
	sllHeader[11] = 0x00 // Padding
	sllHeader[12] = 0x86 // Protocol type: IPv6 (high byte)
	sllHeader[13] = 0xDD // Protocol type: IPv6 (low byte)

	ip := &layers.IPv6{
		Version:    6,
		HopLimit:   64,
		SrcIP:      net.ParseIP(srcIP).To16(),
		DstIP:      net.ParseIP(dstIP).To16(),
		NextHeader: layers.IPProtocolTCP,
	}

	tcp := &layers.TCP{
		SrcPort: layers.TCPPort(srcPort),
		DstPort: layers.TCPPort(dstPort),
		Seq:     1,
		ACK:     true,
		Window:  65535,
	}
	if err := tcp.SetNetworkLayerForChecksum(ip); err != nil {
		t.Fatalf("SetNetworkLayerForChecksum() error = %v", err)
	}

	buf := gopacket.NewSerializeBuffer()
	opts := gopacket.SerializeOptions{
		FixLengths:       true,
		ComputeChecksums: true,
	}

	if err := gopacket.SerializeLayers(buf, opts, ip, tcp, gopacket.Payload(payload)); err != nil {
		t.Fatalf("SerializeLayers() error = %v", err)
	}

	// Prepend SLL header
	packetData := append(sllHeader, buf.Bytes()...)

	return api.RawPacket{
		Data:      packetData,
		Timestamp: time.Now().UnixNano(),
		LinkType:  101, // Linux SLL
	}
}

// TestParser_SLLPacketType tests different SLL packet types
func TestParser_SLLPacketType(t *testing.T) {
	// Test that the parser handles SLL packets with different packet types
	p := NewParser()
	defer p.Close()

	// PACKET_HOST (0) - packet destined for local host
	srcIP := "192.168.1.100"
	dstIP := "10.0.0.1"
	srcPort := uint16(54321)
	dstPort := uint16(443)

	clientHello := createTLSClientHello(0x0303)

	pkt := buildSLLRawPacket(t, srcIP, dstIP, srcPort, dstPort, clientHello)

	result, err := p.Process(pkt)
	if err != nil {
		t.Fatalf("Process() error = %v", err)
	}
	if result == nil {
		t.Fatal("Process() should return TLSClientHello for PACKET_HOST")
	}
}

// buildSYNPacket creates a raw SYN packet (no payload) with TCP options
func buildSYNPacket(t *testing.T, srcIP, dstIP string, srcPort, dstPort uint16, mss uint16, windowScale uint8) api.RawPacket {
	t.Helper()

	ip := &layers.IPv4{
		Version:  4,
		TTL:      64,
		Id:       0x1234,
		Flags:    layers.IPv4DontFragment,
		SrcIP:    net.ParseIP(srcIP).To4(),
		DstIP:    net.ParseIP(dstIP).To4(),
		Protocol: layers.IPProtocolTCP,
	}

	tcp := &layers.TCP{
		SrcPort: layers.TCPPort(srcPort),
		DstPort: layers.TCPPort(dstPort),
		Seq:     1000,
		SYN:     true,
		Window:  65535,
		Options: []layers.TCPOption{
			{
				OptionType:   layers.TCPOptionKindMSS,
				OptionLength: 4,
				OptionData:   []byte{byte(mss >> 8), byte(mss)},
			},
			{
				OptionType:   layers.TCPOptionKindWindowScale,
				OptionLength: 3,
				OptionData:   []byte{windowScale},
			},
			{
				OptionType:   layers.TCPOptionKindSACKPermitted,
				OptionLength: 2,
			},
		},
	}
	if err := tcp.SetNetworkLayerForChecksum(ip); err != nil {
		t.Fatalf("SetNetworkLayerForChecksum() error = %v", err)
	}

	eth := &layers.Ethernet{
		SrcMAC:       net.HardwareAddr{0x00, 0x11, 0x22, 0x33, 0x44, 0x55},
		DstMAC:       net.HardwareAddr{0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff},
		EthernetType: layers.EthernetTypeIPv4,
	}

	buf := gopacket.NewSerializeBuffer()
	opts := gopacket.SerializeOptions{
		FixLengths:       true,
		ComputeChecksums: true,
	}

	if err := gopacket.SerializeLayers(buf, opts, eth, ip, tcp); err != nil {
		t.Fatalf("SerializeLayers() error = %v", err)
	}

	return api.RawPacket{
		Data:      buf.Bytes(),
		Timestamp: time.Now().UnixNano(),
		LinkType:  1,
	}
}

func TestProcess_SYNCreatesFlowWithTCPMeta(t *testing.T) {
	parser := NewParser()
	defer parser.Close()

	srcIP := "192.168.1.50"
	dstIP := "10.0.0.1"
	srcPort := uint16(44444)
	dstPort := uint16(443)
	expectedMSS := uint16(1460)
	expectedWS := uint8(7)

	// Step 1: Send SYN packet (should create flow, return nil)
	synPkt := buildSYNPacket(t, srcIP, dstIP, srcPort, dstPort, expectedMSS, expectedWS)
	ch, err := parser.Process(synPkt)
	if err != nil {
		t.Fatalf("Process(SYN) error = %v", err)
	}
	if ch != nil {
		t.Fatal("Process(SYN) should return nil (no ClientHello yet)")
	}

	// Verify flow was created with correct metadata
	key := flowKey(srcIP, srcPort, dstIP, dstPort)
	parser.mu.RLock()
	flow, exists := parser.flows[key]
	parser.mu.RUnlock()

	if !exists {
		t.Fatal("SYN should create a flow")
	}

	flow.mu.Lock()
	if flow.State != NEW {
		t.Errorf("flow state = %v, want NEW", flow.State)
	}
	if flow.TCPMeta.MSS != expectedMSS {
		t.Errorf("flow TCPMeta.MSS = %d, want %d", flow.TCPMeta.MSS, expectedMSS)
	}
	if flow.TCPMeta.WindowScale != expectedWS {
		t.Errorf("flow TCPMeta.WindowScale = %d, want %d", flow.TCPMeta.WindowScale, expectedWS)
	}
	if flow.TCPMeta.WindowSize != 65535 {
		t.Errorf("flow TCPMeta.WindowSize = %d, want 65535", flow.TCPMeta.WindowSize)
	}
	// Check SACK is in options
	hasSACK := false
	for _, opt := range flow.TCPMeta.Options {
		if opt == "SACK" {
			hasSACK = true
		}
	}
	if !hasSACK {
		t.Errorf("flow TCPMeta.Options = %v, want SACK", flow.TCPMeta.Options)
	}
	if flow.IPMeta.TTL != 64 {
		t.Errorf("flow IPMeta.TTL = %d, want 64", flow.IPMeta.TTL)
	}
	if !flow.IPMeta.DF {
		t.Error("flow IPMeta.DF should be true")
	}
	flow.mu.Unlock()

	// Step 2: Send ClientHello data packet (SYN had Seq=1000, so data starts at 1001)
	clientHello := createTLSClientHello(0x0303)
	dataPkt := buildRawPacketWithSeq(t, srcIP, dstIP, srcPort, dstPort, clientHello, 1001)

	result, err := parser.Process(dataPkt)
	if err != nil {
		t.Fatalf("Process(ClientHello) error = %v", err)
	}
	if result == nil {
		t.Fatal("Process(ClientHello) should return TLSClientHello")
	}

	// Verify result uses TCP metadata from SYN, not from data packet
	if result.TCPMeta.MSS != expectedMSS {
		t.Errorf("result TCPMeta.MSS = %d, want %d (from SYN)", result.TCPMeta.MSS, expectedMSS)
	}
	if result.TCPMeta.WindowScale != expectedWS {
		t.Errorf("result TCPMeta.WindowScale = %d, want %d (from SYN)", result.TCPMeta.WindowScale, expectedWS)
	}
	if result.IPMeta.TTL != 64 {
		t.Errorf("result IPMeta.TTL = %d, want 64 (from SYN)", result.IPMeta.TTL)
	}
	if !result.IPMeta.DF {
		t.Error("result IPMeta.DF should be true (from SYN)")
	}
}

func TestProcess_SynToCHMs_Timing(t *testing.T) {
	parser := NewParser()
	defer parser.Close()

	srcIP := "192.168.1.60"
	dstIP := "10.0.0.1"
	srcPort := uint16(55555)
	dstPort := uint16(443)

	// Step 1: Send SYN
	synPkt := buildSYNPacket(t, srcIP, dstIP, srcPort, dstPort, 1460, 7)
	_, err := parser.Process(synPkt)
	if err != nil {
		t.Fatalf("Process(SYN) error = %v", err)
	}

	// Wait a measurable amount of time
	time.Sleep(50 * time.Millisecond)

	// Step 2: Send ClientHello (SYN had Seq=1000, data at 1001)
	clientHello := createTLSClientHello(0x0303)
	dataPkt := buildRawPacketWithSeq(t, srcIP, dstIP, srcPort, dstPort, clientHello, 1001)

	result, err := parser.Process(dataPkt)
	if err != nil {
		t.Fatalf("Process(ClientHello) error = %v", err)
	}
	if result == nil {
		t.Fatal("Process(ClientHello) should return TLSClientHello")
	}

	if result.SynToCHMs == nil {
		t.Fatal("SynToCHMs should not be nil")
	}

	// SynToCHMs should be at least 50ms (we slept 50ms)
	if *result.SynToCHMs < 40 {
		t.Errorf("SynToCHMs = %d ms, want >= 40ms (slept 50ms)", *result.SynToCHMs)
	}
}

func TestProcess_NoSYN_StillWorks(t *testing.T) {
	// Ensure backward compatibility: if no SYN is seen (e.g. capture started
	// mid-connection), a ClientHello data packet still creates a flow and works.
	parser := NewParser()
	defer parser.Close()

	srcIP := "192.168.1.70"
	dstIP := "10.0.0.1"
	srcPort := uint16(55666)
	dstPort := uint16(443)

	clientHello := createTLSClientHello(0x0303)
	dataPkt := buildRawPacket(t, srcIP, dstIP, srcPort, dstPort, clientHello)

	result, err := parser.Process(dataPkt)
	if err != nil {
		t.Fatalf("Process() error = %v", err)
	}
	if result == nil {
		t.Fatal("Process() should return TLSClientHello even without SYN")
	}
	if result.SrcIP != srcIP {
		t.Errorf("SrcIP = %v, want %v", result.SrcIP, srcIP)
	}
}

func TestProcess_FragmentedClientHello_UsesFlowMeta(t *testing.T) {
	parser := NewParser()
	defer parser.Close()

	srcIP := "192.168.1.80"
	dstIP := "10.0.0.1"
	srcPort := uint16(33333)
	dstPort := uint16(443)
	expectedMSS := uint16(1460)
	expectedWS := uint8(7)

	// Step 1: Send SYN with TCP options
	synPkt := buildSYNPacket(t, srcIP, dstIP, srcPort, dstPort, expectedMSS, expectedWS)
	_, err := parser.Process(synPkt)
	if err != nil {
		t.Fatalf("Process(SYN) error = %v", err)
	}

	// Step 2: Send incomplete TLS record (fragment 1, Seq=1001)
	clientHello := createTLSClientHello(0x0303)
	half := len(clientHello) / 2
	fragment1 := clientHello[:half]

	pkt1 := buildRawPacketWithSeq(t, srcIP, dstIP, srcPort, dstPort, fragment1, 1001)
	ch, err := parser.Process(pkt1)
	if err != nil {
		t.Fatalf("Process(fragment1) error = %v", err)
	}
	if ch != nil {
		t.Fatal("Process(fragment1) should return nil (incomplete)")
	}

	// Step 3: Send rest (fragment 2, Seq=1001+len(fragment1))
	fragment2 := clientHello[half:]
	pkt2 := buildRawPacketWithSeq(t, srcIP, dstIP, srcPort, dstPort, fragment2, 1001+uint32(half))
	result, err := parser.Process(pkt2)
	if err != nil {
		t.Fatalf("Process(fragment2) error = %v", err)
	}
	if result == nil {
		t.Fatal("Process(fragment2) should return complete TLSClientHello")
	}

	// Verify metadata comes from the SYN (flow), not from the last data fragment
	if result.TCPMeta.MSS != expectedMSS {
		t.Errorf("result TCPMeta.MSS = %d, want %d (from SYN)", result.TCPMeta.MSS, expectedMSS)
	}
	if result.TCPMeta.WindowScale != expectedWS {
		t.Errorf("result TCPMeta.WindowScale = %d, want %d (from SYN)", result.TCPMeta.WindowScale, expectedWS)
	}
	if result.IPMeta.TTL != 64 {
		t.Errorf("result IPMeta.TTL = %d, want 64 (from SYN)", result.IPMeta.TTL)
	}
}

func TestProcess_TCPRetransmission_Ignored(t *testing.T) {
	parser := NewParser()
	defer parser.Close()

	srcIP := "192.168.1.90"
	dstIP := "10.0.0.1"
	srcPort := uint16(44321)
	dstPort := uint16(443)

	// Step 1: Send SYN (Seq=1000)
	synPkt := buildSYNPacket(t, srcIP, dstIP, srcPort, dstPort, 1460, 7)
	_, _ = parser.Process(synPkt)

	// Step 2: Send first fragment (Seq=1001)
	clientHello := createTLSClientHello(0x0303)
	half := len(clientHello) / 2
	fragment1 := clientHello[:half]
	pkt1 := buildRawPacketWithSeq(t, srcIP, dstIP, srcPort, dstPort, fragment1, 1001)
	_, _ = parser.Process(pkt1)

	// Step 3: Retransmit fragment 1 (same Seq=1001) — should be ignored
	pkt1dup := buildRawPacketWithSeq(t, srcIP, dstIP, srcPort, dstPort, fragment1, 1001)
	ch, err := parser.Process(pkt1dup)
	if err != nil {
		t.Fatalf("Process(retransmit) error = %v", err)
	}
	if ch != nil {
		t.Fatal("Process(retransmit) should return nil")
	}

	// Step 4: Send second fragment (correct Seq)
	fragment2 := clientHello[half:]
	pkt2 := buildRawPacketWithSeq(t, srcIP, dstIP, srcPort, dstPort, fragment2, 1001+uint32(half))
	result, err := parser.Process(pkt2)
	if err != nil {
		t.Fatalf("Process(fragment2) error = %v", err)
	}
	if result == nil {
		t.Fatal("Process(fragment2) should return complete TLSClientHello after retransmission")
	}
}

func TestProcess_TCPGap_DropsFlow(t *testing.T) {
	parser := NewParser()
	defer parser.Close()

	srcIP := "192.168.1.91"
	dstIP := "10.0.0.1"
	srcPort := uint16(44322)
	dstPort := uint16(443)

	// Step 1: Send SYN (Seq=1000)
	synPkt := buildSYNPacket(t, srcIP, dstIP, srcPort, dstPort, 1460, 7)
	_, _ = parser.Process(synPkt)

	// Step 2: Send first fragment (Seq=1001)
	clientHello := createTLSClientHello(0x0303)
	half := len(clientHello) / 2
	fragment1 := clientHello[:half]
	pkt1 := buildRawPacketWithSeq(t, srcIP, dstIP, srcPort, dstPort, fragment1, 1001)
	_, _ = parser.Process(pkt1)

	// Step 3: Send fragment with gap (Seq far ahead) — should drop flow
	fragment2 := clientHello[half:]
	gapSeq := uint32(1001 + half + 100) // 100 bytes gap
	pkt2 := buildRawPacketWithSeq(t, srcIP, dstIP, srcPort, dstPort, fragment2, gapSeq)
	ch, err := parser.Process(pkt2)
	if err != nil {
		t.Fatalf("Process(gap) error = %v", err)
	}
	if ch != nil {
		t.Fatal("Process(gap) should return nil")
	}

	// Verify flow was NOT removed (gap handling now continues with available data)
	key := flowKey(srcIP, srcPort, dstIP, dstPort)
	parser.mu.RLock()
	_, exists := parser.flows[key]
	parser.mu.RUnlock()
	if !exists {
		t.Fatal("flow should NOT be removed after sequence gap (gap handling changed)")
	}
	// Verify gap was detected (counter incremented)
	_, gapDetected, _, _ := parser.GetMetrics()
	if gapDetected == 0 {
		t.Fatal("gapDetected counter should be incremented")
	}
}

// createTLS13ClientHelloWithSNI creates a TLS 1.3 ClientHello (record version 0x0303,
// supported_versions extension includes 0x0304)
func createTLS13ClientHelloWithSNI(sni string) []byte {
	// Build SNI extension
	sniExt := buildSNIExtension(sni)

	// Build ALPN extension
	alpnExt := buildALPNExtension([]string{"h2", "http/1.1"})

	// Build supported_versions extension with TLS 1.3 (0x0304) and TLS 1.2 (0x0303)
	// Extension type: 43 (0x002b), data: list_len(1) + 2 versions (4 bytes)
	supportedVersionsExt := []byte{
		0x00, 0x2b, // Extension type: supported_versions (43)
		0x00, 0x05, // Extension data length: 5
		0x04,       // Supported versions list length: 4 bytes (2 versions)
		0x03, 0x04, // TLS 1.3
		0x03, 0x03, // TLS 1.2
	}

	// Combine extensions
	extensions := append(sniExt, alpnExt...)
	extensions = append(extensions, supportedVersionsExt...)
	extLen := len(extensions)

	// Cipher suites (TLS 1.3 suites)
	cipherSuites := []byte{0x00, 0x04, 0x13, 0x01, 0x13, 0x02, 0xc0, 0x2f}

	// Compression methods (null only)
	compressionMethods := []byte{0x01, 0x00}

	// Build ClientHello handshake body
	handshakeBody := []byte{
		0x03, 0x03, // Version: TLS 1.2 (mandatory for TLS 1.3 ClientHello)
	}
	// Random (32 bytes)
	for i := 0; i < 32; i++ {
		handshakeBody = append(handshakeBody, 0x01)
	}
	handshakeBody = append(handshakeBody, 0x00) // Session ID length: 0

	// Add cipher suites
	cipherSuiteLen := len(cipherSuites)
	handshakeBody = append(handshakeBody, byte(cipherSuiteLen>>8), byte(cipherSuiteLen))
	handshakeBody = append(handshakeBody, cipherSuites...)

	// Add compression methods
	handshakeBody = append(handshakeBody, compressionMethods...)

	// Add extensions
	handshakeBody = append(handshakeBody, byte(extLen>>8), byte(extLen))
	handshakeBody = append(handshakeBody, extensions...)

	// Build handshake with type and length
	handshakeLen := len(handshakeBody)
	handshake := append([]byte{
		0x01, // Handshake type: ClientHello
		byte(handshakeLen >> 16), byte(handshakeLen >> 8), byte(handshakeLen),
	}, handshakeBody...)

	// Build TLS record (version always 0x0303 for TLS 1.3)
	recordLen := len(handshake)
	record := make([]byte, 5+recordLen)
	record[0] = 0x16 // Handshake
	record[1] = 0x03 // TLS 1.2 in record layer (per TLS 1.3 spec)
	record[2] = 0x03
	record[3] = byte(recordLen >> 8)
	record[4] = byte(recordLen)
	copy(record[5:], handshake)

	return record
}

func TestExtractTLSExtensions_TLS13(t *testing.T) {
	payload := createTLS13ClientHelloWithSNI("example.com")

	info, err := extractTLSExtensions(payload)
	if err != nil {
		t.Fatalf("extractTLSExtensions() error = %v", err)
	}
	if info == nil {
		t.Fatal("extractTLSExtensions() returned nil")
	}

	// TLS 1.3 should be detected via supported_versions extension
	if info.TLSVersion != "1.3" {
		t.Errorf("TLSVersion = %q, want \"1.3\"", info.TLSVersion)
	}
	if info.SNI != "example.com" {
		t.Errorf("SNI = %q, want \"example.com\"", info.SNI)
	}
}

func TestProcess_TLS13ClientHello_CorrectVersion(t *testing.T) {
	parser := NewParser()
	defer parser.Close()

	srcIP := "192.168.1.200"
	dstIP := "10.0.0.1"
	srcPort := uint16(44555)
	dstPort := uint16(443)

	clientHello := createTLS13ClientHelloWithSNI("tls13.example.com")
	pkt := buildRawPacket(t, srcIP, dstIP, srcPort, dstPort, clientHello)

	result, err := parser.Process(pkt)
	if err != nil {
		t.Fatalf("Process() error = %v", err)
	}
	if result == nil {
		t.Fatal("Process() should return TLSClientHello")
	}

	if result.TLSVersion != "1.3" {
		t.Errorf("TLSVersion = %q, want \"1.3\"", result.TLSVersion)
	}
	if result.SNI != "tls13.example.com" {
		t.Errorf("SNI = %q, want \"tls13.example.com\"", result.SNI)
	}
}

// TestProcess_MissedSYN_NoFalseRetransmit verifies Bug 7 fix:
// when SYN is missed, the first data packet must NOT increment retransmitCount
// even though seq < NextSeq would evaluate to true (because NextSeq was
// initialised from that very same packet).
func TestProcess_MissedSYN_NoFalseRetransmit(t *testing.T) {
parser := NewParser()
defer parser.Close()

srcIP := "10.0.0.1"
dstIP := "10.0.0.2"
srcPort := uint16(12345)
dstPort := uint16(443)

// Build a minimal TLS ClientHello payload.
payload := createMinimalTLSClientHelloWithSNIAndALPN("test.example.com", nil)

// Send without a preceding SYN — seq starts from 100.
pkt := buildRawPacketWithSeq(t, srcIP, dstIP, srcPort, dstPort, payload, 100)
_, err := parser.Process(pkt)
if err != nil {
t.Fatalf("Process() error: %v", err)
}

retransmit, _, _, _ := parser.GetMetrics()
if retransmit != 0 {
t.Errorf("retransmitCount = %d after first packet on a new flow (SYN missed); want 0", retransmit)
}
}