fix: decode jt808 registration plate text

go/vehicle-gateway/internal/protocol/jt808/parser.go

@@ -1,14 +1,17 @@
 package jt808
 
 import (
+	"bytes"
 	"encoding/binary"
 	"encoding/hex"
 	"errors"
 	"fmt"
 	"strings"
 	"time"
+	"unicode/utf8"
 
 	"lingniu-vehicle-ingest/go/vehicle-gateway/internal/envelope"
+	"golang.org/x/text/encoding/simplifiedchinese"
 )
 
 var (
@@ -318,7 +321,18 @@ func fixedText(data []byte) string {
 }
 
 func freeText(data []byte) string {
-	return strings.TrimRight(strings.TrimSpace(string(data)), "\x00")
+	data = bytes.Trim(data, "\x00 ")
+	if len(data) == 0 {
+		return ""
+	}
+	if utf8.Valid(data) {
+		return string(data)
+	}
+	decoded, err := simplifiedchinese.GBK.NewDecoder().Bytes(data)
+	if err == nil && utf8.Valid(decoded) {
+		return string(decoded)
+	}
+	return strings.ToValidUTF8(string(data), "")
 }
 
 func parseBCDTime(data []byte) time.Time {

go/vehicle-gateway/internal/protocol/jt808/parser_test.go

@@ -153,6 +153,25 @@ func TestParseFrameParsesRegistrationIdentity(t *testing.T) {
 	}
 }
 
+func TestParseFrameDecodesGBKRegistrationPlate(t *testing.T) {
+	body := make([]byte, 0, 46)
+	body = binary.BigEndian.AppendUint16(body, 16)
+	body = binary.BigEndian.AppendUint16(body, 32)
+	body = appendFixedASCII(body, "YUTNG", 5)
+	body = appendFixedASCII(body, "ZK6105CHEVNPG4", 20)
+	body = appendFixedASCII(body, "DEV0002", 7)
+	body = append(body, 2)
+	body = append(body, []byte{0xBB, 0xA6, 'A', '5', '3', '3', '0', '1'}...)
+
+	env, err := ParseFrame(buildFrame(0x0100, "013079963380", 9, body), 1782918600000, "115.231.168.135:43625")
+	if err != nil {
+		t.Fatalf("ParseFrame() error = %v", err)
+	}
+	if env.Plate != "沪A53301" {
+		t.Fatalf("plate = %q", env.Plate)
+	}
+}
+
 func TestParseFrameParsesAuthenticationToken(t *testing.T) {
 	env, err := ParseFrame(buildFrame(0x0102, "064646848757", 8, []byte("g7gps")), 1782918600000, "115.231.168.135:43625")
 	if err != nil {