fix: format daily metric query timestamps

go/vehicle-gateway/internal/stats/query.go

@@ -9,6 +9,7 @@ import (
 	"net/http"
 	"strconv"
 	"strings"
+	"time"
 )
 
 type Queryer interface {
@@ -63,11 +64,14 @@ func (r *MetricRepository) Query(ctx context.Context, query MetricQuery) ([]Metr
 	var out []MetricRow
 	for rows.Next() {
 		var row MetricRow
+		var statDate scanDate
+		var createdAt scanDateTime
+		var updatedAt scanDateTime
 		var first sql.NullFloat64
 		var latest sql.NullFloat64
 		if err := rows.Scan(
 			&row.VIN,
-			&row.StatDate,
+			&statDate,
 			&row.Protocol,
 			&row.MetricKey,
 			&row.MetricValue,
@@ -76,11 +80,14 @@ func (r *MetricRepository) Query(ctx context.Context, query MetricQuery) ([]Metr
 			&latest,
 			&row.SampleCount,
 			&row.CalculationMethod,
-			&row.CreatedAt,
+			&createdAt,
-			&row.UpdatedAt,
+			&updatedAt,
 		); err != nil {
 			return nil, err
 		}
+		row.StatDate = statDate.String
+		row.CreatedAt = createdAt.String
+		row.UpdatedAt = updatedAt.String
 		if first.Valid {
 			row.FirstTotalMileageKM = &first.Float64
 		}
@@ -239,3 +246,36 @@ func writeMetricError(w http.ResponseWriter, status int, message string) {
 	w.WriteHeader(status)
 	_ = json.NewEncoder(w).Encode(map[string]any{"error": message})
 }
+
+type scanDate struct {
+	String string
+}
+
+func (s *scanDate) Scan(value any) error {
+	s.String = formatSQLTime(value, "2006-01-02")
+	return nil
+}
+
+type scanDateTime struct {
+	String string
+}
+
+func (s *scanDateTime) Scan(value any) error {
+	s.String = formatSQLTime(value, "2006-01-02 15:04:05")
+	return nil
+}
+
+func formatSQLTime(value any, layout string) string {
+	switch typed := value.(type) {
+	case nil:
+		return ""
+	case time.Time:
+		return typed.Format(layout)
+	case []byte:
+		return strings.TrimSpace(string(typed))
+	case string:
+		return strings.TrimSpace(typed)
+	default:
+		return strings.TrimSpace(fmt.Sprint(typed))
+	}
+}

go/vehicle-gateway/internal/stats/query_test.go

@@ -7,6 +7,7 @@ import (
 	"net/http/httptest"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/DATA-DOG/go-sqlmock"
 )
@@ -24,8 +25,8 @@ func TestMetricRepositoryQueriesDailyMetricsWithFilters(t *testing.T) {
 			"first_total_mileage_km", "latest_total_mileage_km", "sample_count", "calculation_method",
 			"created_at", "updated_at",
 		}).AddRow(
-			"LKLG7C4E3NA774736", "2026-07-01", "JT808", MetricDailyTotalMileageKM, 12345.6, "km",
+			"LKLG7C4E3NA774736", time.Date(2026, 7, 1, 0, 0, 0, 0, time.FixedZone("Asia/Shanghai", 8*3600)), "JT808", MetricDailyTotalMileageKM, 12345.6, "km",
-			12345.6, 12345.6, 13, "TOTAL_MILEAGE_DIFF", "2026-07-01 22:49:11", "2026-07-01 23:09:36",
+			12345.6, 12345.6, 13, "TOTAL_MILEAGE_DIFF", time.Date(2026, 7, 1, 22, 49, 11, 0, time.FixedZone("Asia/Shanghai", 8*3600)), time.Date(2026, 7, 1, 23, 9, 36, 0, time.FixedZone("Asia/Shanghai", 8*3600)),
 		))
 
 	repository := NewMetricRepository(db)
@@ -45,6 +46,9 @@ func TestMetricRepositoryQueriesDailyMetricsWithFilters(t *testing.T) {
 	if rows[0].MetricKey != MetricDailyTotalMileageKM || rows[0].MetricValue != 12345.6 {
 		t.Fatalf("unexpected row: %#v", rows[0])
 	}
+	if rows[0].StatDate != "2026-07-01" || rows[0].UpdatedAt != "2026-07-01 23:09:36" {
+		t.Fatalf("unexpected time formatting: %#v", rows[0])
+	}
 	if err := mock.ExpectationsWereMet(); err != nil {
 		t.Fatalf("sql expectations: %v", err)
 	}