package gateway

import (
	"context"
	"encoding/hex"
	"io"
	"log/slog"
	"net"
	"strings"
	"testing"
	"time"

	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/envelope"
	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/metrics"
	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/protocol/gb32960"
	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/protocol/jt808"
)

func TestTCPServerPublishesGoodFrameOnlyToRawByDefault(t *testing.T) {
	frame, err := hex.DecodeString("7E020000320133077954250001000000000048000301D2C4C707376139000A00E6004F26063016235701040001900C2504000000000202000030011F31010F867E")
	if err != nil {
		t.Fatal(err)
	}
	sink := &recordingSink{}
	server := newTestServer(t, TCPProtocol{
		Protocol: envelope.ProtocolJT808,
		Addr:     ":0",
		Extract:  jt808.ExtractFrames,
		Parse:    jt808.ParseFrame,
	}, sink)

	client, done := runPipe(t, server)
	if _, err := client.Write(frame); err != nil {
		t.Fatalf("client.Write() error = %v", err)
	}
	_ = client.Close()
	<-done

	if len(sink.raw) != 1 || len(sink.unified) != 0 {
		t.Fatalf("raw=%d unified=%d", len(sink.raw), len(sink.unified))
	}
	if sink.raw[0].Phone != "13307795425" {
		t.Fatalf("phone = %q", sink.raw[0].Phone)
	}
	if sink.raw[0].Fields[envelope.FieldTotalMileageKM] != 10241.2 {
		t.Fatalf("total mileage = %#v", sink.raw[0].Fields[envelope.FieldTotalMileageKM])
	}
}

func TestTCPServerRecordsFrameMetrics(t *testing.T) {
	registry := metrics.NewRegistry()
	server, err := NewTCPServer(TCPServerConfig{
		Protocol: TCPProtocol{
			Protocol: envelope.ProtocolJT808,
			Addr:     ":0",
			Extract:  jt808.ExtractFrames,
			Parse: func(_ []byte, receivedAtMS int64, sourceEndpoint string) (envelope.FrameEnvelope, error) {
				return envelope.FrameEnvelope{
					Protocol:       envelope.ProtocolJT808,
					MessageID:      "0x0200",
					Phone:          "13307795425",
					SourceEndpoint: sourceEndpoint,
					ReceivedAtMS:   receivedAtMS,
					EventTimeMS:    receivedAtMS,
					ParseStatus:    envelope.ParseOK,
				}, nil
			},
		},
		Sink:    &recordingSink{},
		Logger:  slog.New(slog.NewTextHandler(testWriter{t: t}, nil)),
		Metrics: registry,
	})
	if err != nil {
		t.Fatalf("NewTCPServer() error = %v", err)
	}

	server.handleFrame(context.Background(), nil, []byte{0x01}, "127.0.0.1:808", &connectionState{})

	text := registry.Render()
	for _, want := range []string{
		`vehicle_gateway_frames_total{protocol="JT808",status="OK"} 1`,
		`vehicle_gateway_identity_total{protocol="JT808",status="unresolved"} 1`,
		`vehicle_gateway_publish_total{kind="raw",protocol="JT808",status="ok"} 1`,
		`vehicle_gateway_frame_duration_ms{protocol="JT808",status="OK"}`,
		`vehicle_gateway_frame_duration_ms_histogram_bucket{le="+Inf",protocol="JT808",status="OK"} 1`,
		`vehicle_gateway_frame_duration_ms_histogram_count{protocol="JT808",status="OK"} 1`,
		`vehicle_gateway_frame_duration_ms_histogram_sum{protocol="JT808",status="OK"}`,
	} {
		if !strings.Contains(text, want) {
			t.Fatalf("metrics missing %s:\n%s", want, text)
		}
	}
	if strings.Contains(text, `kind="unified"`) {
		t.Fatalf("unified publish metric should not be recorded by default:\n%s", text)
	}
}

func TestTCPServerRecordsActiveConnectionGauge(t *testing.T) {
	registry := metrics.NewRegistry()
	server, err := NewTCPServer(TCPServerConfig{
		Protocol: TCPProtocol{
			Protocol: envelope.ProtocolJT808,
			Addr:     ":0",
			Extract:  jt808.ExtractFrames,
			Parse:    jt808.ParseFrame,
		},
		Sink:        &recordingSink{},
		Logger:      slog.New(slog.NewTextHandler(testWriter{t: t}, nil)),
		Metrics:     registry,
		IdleTimeout: time.Minute,
	})
	if err != nil {
		t.Fatalf("NewTCPServer() error = %v", err)
	}
	client, srv := net.Pipe()
	opened := make(chan struct{})
	done := make(chan struct{})
	go func() {
		close(opened)
		server.handleConnection(context.Background(), srv)
		close(done)
	}()
	<-opened
	deadline := time.Now().Add(2 * time.Second)
	for time.Now().Before(deadline) {
		if strings.Contains(registry.Render(), `vehicle_gateway_active_connections{protocol="JT808"} 1`) {
			break
		}
		time.Sleep(10 * time.Millisecond)
	}
	if text := registry.Render(); !strings.Contains(text, `vehicle_gateway_active_connections{protocol="JT808"} 1`) {
		t.Fatalf("active connection gauge missing while open:\n%s", text)
	}

	_ = client.Close()
	<-done

	if text := registry.Render(); !strings.Contains(text, `vehicle_gateway_active_connections{protocol="JT808"} 0`) {
		t.Fatalf("active connection gauge should return to zero:\n%s", text)
	}
}

func TestTCPServerRecordsConnectionRejectionMetric(t *testing.T) {
	registry := metrics.NewRegistry()
	server, err := NewTCPServer(TCPServerConfig{
		Protocol: TCPProtocol{
			Protocol: envelope.ProtocolJT808,
			Addr:     ":0",
			Extract:  jt808.ExtractFrames,
			Parse:    jt808.ParseFrame,
		},
		Sink:    &recordingSink{},
		Logger:  slog.New(slog.NewTextHandler(testWriter{t: t}, nil)),
		Metrics: registry,
	})
	if err != nil {
		t.Fatalf("NewTCPServer() error = %v", err)
	}

	server.recordConnectionRejection("max_connections")

	if text := registry.Render(); !strings.Contains(text, `vehicle_gateway_connection_rejections_total{protocol="JT808",reason="max_connections"} 1`) {
		t.Fatalf("connection rejection metric missing:\n%s", text)
	}
}

func TestTCPServerRecordsConnectionCloseReasonMetric(t *testing.T) {
	registry := metrics.NewRegistry()
	server, err := NewTCPServer(TCPServerConfig{
		Protocol: TCPProtocol{
			Protocol: envelope.ProtocolJT808,
			Addr:     ":0",
			Extract:  jt808.ExtractFrames,
			Parse:    jt808.ParseFrame,
		},
		Sink:    &recordingSink{},
		Logger:  slog.New(slog.NewTextHandler(testWriter{t: t}, nil)),
		Metrics: registry,
	})
	if err != nil {
		t.Fatalf("NewTCPServer() error = %v", err)
	}

	server.recordConnectionClose("read_timeout")

	if text := registry.Render(); !strings.Contains(text, `vehicle_gateway_connection_closes_total{protocol="JT808",reason="read_timeout"} 1`) {
		t.Fatalf("connection close metric missing:\n%s", text)
	}
}

func TestTCPServerPublishesBadFrameOnlyToRaw(t *testing.T) {
	good := buildGBFrame(0x02, 0xfe, "LNBSCB3D4R1234567", nil)
	good[len(good)-1] ^= 0xff
	sink := &recordingSink{}
	registry := metrics.NewRegistry()
	server := newTestServer(t, TCPProtocol{
		Protocol: envelope.ProtocolGB32960,
		Addr:     ":0",
		Extract:  gb32960.ExtractFrames,
		Parse:    gb32960.ParseFrame,
	}, sink)
	server.metrics = registry

	client, done := runPipe(t, server)
	if _, err := client.Write(good); err != nil {
		t.Fatalf("client.Write() error = %v", err)
	}
	_ = client.Close()
	<-done

	if len(sink.raw) != 1 || len(sink.unified) != 0 {
		t.Fatalf("raw=%d unified=%d", len(sink.raw), len(sink.unified))
	}
	if sink.raw[0].ParseStatus != envelope.ParseBadFrame {
		t.Fatalf("parse status = %q", sink.raw[0].ParseStatus)
	}
	if sink.raw[0].ParseError == "" {
		t.Fatal("parse error should be recorded")
	}
	if text := registry.Render(); !strings.Contains(text, `vehicle_gateway_parse_errors_total{protocol="GB32960",reason="checksum"} 1`) {
		t.Fatalf("parse error metric missing:\n%s", text)
	}
}

func TestTCPServerAnnotatesUnresolvedIdentity(t *testing.T) {
	sink := &recordingSink{}
	server := newTestServer(t, TCPProtocol{
		Protocol: envelope.ProtocolJT808,
		Addr:     ":0",
		Extract: func(raw []byte) ([][]byte, []byte, error) {
			return [][]byte{raw}, nil, nil
		},
		Parse: func(_ []byte, receivedAtMS int64, sourceEndpoint string) (envelope.FrameEnvelope, error) {
			return envelope.FrameEnvelope{
				Protocol:       envelope.ProtocolJT808,
				MessageID:      "0x0200",
				Phone:          "13307795425",
				SourceEndpoint: sourceEndpoint,
				ReceivedAtMS:   receivedAtMS,
				EventTimeMS:    receivedAtMS,
				ParseStatus:    envelope.ParseOK,
			}, nil
		},
	}, sink)

	server.handleFrame(context.Background(), nil, []byte{0x01}, "127.0.0.1:808", &connectionState{})

	if len(sink.raw) != 1 {
		t.Fatalf("raw count = %d", len(sink.raw))
	}
	identity, ok := sink.raw[0].Parsed["identity"].(map[string]any)
	if !ok || identity["resolved"] != false || identity["reason"] != "no_binding" {
		t.Fatalf("identity metadata = %#v", sink.raw[0].Parsed["identity"])
	}
}

func TestTCPServerWritesProtocolResponseAfterPublish(t *testing.T) {
	frame := buildGBFrame(0x07, 0xfe, "LNBSCB3D4R1234567", nil)
	sink := &recordingSink{}
	server := newTestServer(t, TCPProtocol{
		Protocol: envelope.ProtocolGB32960,
		Addr:     ":0",
		Extract:  gb32960.ExtractFrames,
		Parse:    gb32960.ParseFrame,
		Respond: func(_ []byte, env envelope.FrameEnvelope) ([]byte, bool, error) {
			if len(sink.raw) != 1 || sink.raw[0].EventID != env.EventID {
				t.Fatalf("response built before raw publish: raw=%d unified=%d", len(sink.raw), len(sink.unified))
			}
			return []byte("ACK"), true, nil
		},
	}, sink)

	client, done := runPipe(t, server)
	if _, err := client.Write(frame); err != nil {
		t.Fatalf("client.Write() error = %v", err)
	}
	buf := make([]byte, 3)
	if _, err := io.ReadFull(client, buf); err != nil {
		t.Fatalf("read response error = %v", err)
	}
	if string(buf) != "ACK" {
		t.Fatalf("response = %q", string(buf))
	}
	_ = client.Close()
	<-done
}

func TestTCPServerUsesUncancelledFrameContextForAlreadyReadFrame(t *testing.T) {
	parent, cancel := context.WithCancel(context.Background())
	cancel()

	resolver := &contextCheckingResolver{}
	sink := &contextCheckingSink{}
	server, err := NewTCPServer(TCPServerConfig{
		Protocol: TCPProtocol{
			Protocol: envelope.ProtocolJT808,
			Addr:     ":0",
			Extract:  jt808.ExtractFrames,
			Parse: func(_ []byte, receivedAtMS int64, sourceEndpoint string) (envelope.FrameEnvelope, error) {
				return envelope.FrameEnvelope{
					Protocol:       envelope.ProtocolJT808,
					MessageID:      "0x0200",
					Phone:          "13307795425",
					SourceEndpoint: sourceEndpoint,
					ReceivedAtMS:   receivedAtMS,
					EventTimeMS:    receivedAtMS,
					ParseStatus:    envelope.ParseOK,
				}, nil
			},
		},
		Sink:     sink,
		Resolver: resolver,
		Logger:   slog.New(slog.NewTextHandler(testWriter{t: t}, nil)),
	})
	if err != nil {
		t.Fatalf("NewTCPServer() error = %v", err)
	}

	server.handleFrame(parent, nil, []byte{0x01}, "127.0.0.1:808", &connectionState{})

	if resolver.ctxErr != nil {
		t.Fatalf("resolver saw cancelled context: %v", resolver.ctxErr)
	}
	if sink.rawCtxErr != nil {
		t.Fatalf("raw publish saw cancelled context: %v", sink.rawCtxErr)
	}
	if sink.unifiedCtxErr != nil {
		t.Fatalf("unified publish saw cancelled context: %v", sink.unifiedCtxErr)
	}
	if sink.rawCount != 1 || sink.unifiedCount != 0 {
		t.Fatalf("raw=%d unified=%d", sink.rawCount, sink.unifiedCount)
	}
}

func TestTCPServerPublishesUnifiedWhenExplicitlyEnabled(t *testing.T) {
	sink := &recordingSink{}
	server := newTestServer(t, TCPProtocol{
		Protocol: envelope.ProtocolJT808,
		Addr:     ":0",
		Extract:  jt808.ExtractFrames,
		Parse: func(_ []byte, receivedAtMS int64, sourceEndpoint string) (envelope.FrameEnvelope, error) {
			return envelope.FrameEnvelope{
				Protocol:       envelope.ProtocolJT808,
				MessageID:      "0x0200",
				Phone:          "13307795425",
				SourceEndpoint: sourceEndpoint,
				ReceivedAtMS:   receivedAtMS,
				EventTimeMS:    receivedAtMS,
				ParseStatus:    envelope.ParseOK,
			}, nil
		},
	}, sink)
	server.publishUnified = true

	server.handleFrame(context.Background(), nil, []byte{0x01}, "127.0.0.1:808", &connectionState{})

	if len(sink.raw) != 1 || len(sink.unified) != 1 {
		t.Fatalf("raw=%d unified=%d", len(sink.raw), len(sink.unified))
	}
}

type contextCheckingResolver struct {
	ctxErr error
}

func (r *contextCheckingResolver) Resolve(ctx context.Context, env envelope.FrameEnvelope) (envelope.FrameEnvelope, error) {
	r.ctxErr = ctx.Err()
	return env, r.ctxErr
}

type contextCheckingSink struct {
	rawCtxErr     error
	unifiedCtxErr error
	fieldsCtxErr  error
	rawCount      int
	unifiedCount  int
	fieldsCount   int
}

func (s *contextCheckingSink) PublishRaw(ctx context.Context, _ envelope.FrameEnvelope) error {
	s.rawCtxErr = ctx.Err()
	s.rawCount++
	return s.rawCtxErr
}

func (s *contextCheckingSink) PublishUnified(ctx context.Context, _ envelope.FrameEnvelope) error {
	s.unifiedCtxErr = ctx.Err()
	s.unifiedCount++
	return s.unifiedCtxErr
}

func (s *contextCheckingSink) PublishFields(ctx context.Context, _ envelope.FrameEnvelope) error {
	s.fieldsCtxErr = ctx.Err()
	s.fieldsCount++
	return s.fieldsCtxErr
}

func (s *contextCheckingSink) Close() error {
	return nil
}

func newTestServer(t *testing.T, protocol TCPProtocol, sink *recordingSink) *TCPServer {
	t.Helper()
	server, err := NewTCPServer(TCPServerConfig{
		Protocol:       protocol,
		Sink:           sink,
		Logger:         slog.New(slog.NewTextHandler(testWriter{t: t}, nil)),
		ReadBufferSize: 1024,
		IdleTimeout:    time.Second,
		MaxConnections: 1,
	})
	if err != nil {
		t.Fatalf("NewTCPServer() error = %v", err)
	}
	return server
}

func runPipe(t *testing.T, server *TCPServer) (net.Conn, <-chan struct{}) {
	t.Helper()
	client, srv := net.Pipe()
	done := make(chan struct{})
	go func() {
		defer close(done)
		server.handleConnection(context.Background(), srv)
	}()
	return client, done
}

type recordingSink struct {
	raw     []envelope.FrameEnvelope
	unified []envelope.FrameEnvelope
	fields  []envelope.FrameEnvelope
}

func (s *recordingSink) PublishRaw(_ context.Context, env envelope.FrameEnvelope) error {
	s.raw = append(s.raw, env)
	return nil
}

func (s *recordingSink) PublishUnified(_ context.Context, env envelope.FrameEnvelope) error {
	s.unified = append(s.unified, env)
	return nil
}

func (s *recordingSink) PublishFields(_ context.Context, env envelope.FrameEnvelope) error {
	s.fields = append(s.fields, env)
	return nil
}

func (s *recordingSink) Close() error {
	return nil
}

type testWriter struct {
	t *testing.T
}

func (w testWriter) Write(p []byte) (int, error) {
	w.t.Log(string(p))
	return len(p), nil
}

func buildGBFrame(command byte, response byte, vin string, body []byte) []byte {
	frame := []byte{'#', '#', command, response}
	vinBytes := []byte(vin)
	if len(vinBytes) < 17 {
		vinBytes = append(vinBytes, make([]byte, 17-len(vinBytes))...)
	}
	frame = append(frame, vinBytes[:17]...)
	frame = append(frame, 0x01, byte(len(body)>>8), byte(len(body)))
	frame = append(frame, body...)
	var bcc byte
	for _, value := range frame[2:] {
		bcc ^= value
	}
	return append(frame, bcc)
}