fix(stats): preserve realtime baseline from current candidate

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

@@ -177,10 +177,18 @@ func (w *Writer) previousBaseline(ctx context.Context, candidate SourceMileageSa
 	if err != nil {
 		return sourceBaseline{}, false, err
 	}
+	if !found {
+		baseline, found, err = lookupCurrentSourceBaseline(ctx, w.query, candidate.VIN, candidate.StatDate, candidate.Protocol, candidate.SourceKey)
+		if err != nil {
+			return sourceBaseline{}, false, err
+		}
+	}
 
-	w.mu.Lock()
+	if found {
-	w.baselineCache[cacheKey] = sourceBaselineCacheEntry{baseline: baseline, found: found}
+		w.mu.Lock()
-	w.mu.Unlock()
+		w.baselineCache[cacheKey] = sourceBaselineCacheEntry{baseline: baseline, found: true}
+		w.mu.Unlock()
+	}
 	return baseline, found, nil
 }
 

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

@@ -278,6 +278,9 @@ func TestWriterAppendWritesNoPreviousBaselineCandidateAndCleansProjection(t *tes
 	mock.ExpectQuery(`SELECT latest_total_mileage_km, latest_event_time FROM vehicle_daily_mileage_source`).
 		WithArgs("LA9GG64L7PBAF4001", "2026-07-07", "JT808", "JT808:13307765812@115.231.168.135").
 		WillReturnRows(sqlmock.NewRows([]string{"latest_total_mileage_km", "latest_event_time"}))
+	mock.ExpectQuery(`SELECT first_total_mileage_km, first_event_time FROM vehicle_daily_mileage_source`).
+		WithArgs("LA9GG64L7PBAF4001", "2026-07-08", "JT808", "JT808:13307765812@115.231.168.135").
+		WillReturnRows(sqlmock.NewRows([]string{"first_total_mileage_km", "first_event_time"}))
 	mock.ExpectExec(`INSERT INTO vehicle_daily_mileage_source`).
 		WithArgs(
 			"LA9GG64L7PBAF4001",
@@ -421,6 +424,95 @@ func TestWriterAppendUsesPreviousSourceBaselineForRealtimeCandidate(t *testing.T
 	}
 }
 
+func TestWriterAppendUsesCurrentOKCandidateWhenPreviousBaselineMissing(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("sqlmock.New() error = %v", err)
+	}
+	defer db.Close()
+
+	loc := time.FixedZone("Asia/Shanghai", 8*3600)
+	writer := NewWriter(db, loc)
+	firstTime := time.Date(2026, 7, 7, 23, 58, 0, 0, loc)
+	currentTime := time.Date(2026, 7, 8, 15, 56, 0, 0, loc)
+	event := envelope.FrameEnvelope{
+		Protocol:       envelope.ProtocolJT808,
+		VIN:            "LA9GG64L7PBAF4001",
+		Phone:          "13307765812",
+		SourceEndpoint: "115.231.168.135:20215",
+		EventTimeMS:    currentTime.UnixMilli(),
+		Fields: map[string]any{
+			"jt808.location.total_mileage_km": 4136.8,
+		},
+	}
+
+	mock.ExpectExec(`INSERT INTO vehicle_data_source`).
+		WithArgs("JT808", "115.231.168.135", "115.231.168.135:20215", sqlmock.AnyArg(), sqlmock.AnyArg()).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+	mock.ExpectQuery(`SELECT latest_total_mileage_km, latest_event_time FROM vehicle_daily_mileage_source`).
+		WithArgs("LA9GG64L7PBAF4001", "2026-07-07", "JT808", "JT808:13307765812@115.231.168.135").
+		WillReturnRows(sqlmock.NewRows([]string{"latest_total_mileage_km", "latest_event_time"}))
+	mock.ExpectQuery(`SELECT first_total_mileage_km, first_event_time FROM vehicle_daily_mileage_source`).
+		WithArgs("LA9GG64L7PBAF4001", "2026-07-08", "JT808", "JT808:13307765812@115.231.168.135").
+		WillReturnRows(sqlmock.NewRows([]string{"first_total_mileage_km", "first_event_time"}).
+			AddRow(4100.8, firstTime))
+	mock.ExpectExec(`INSERT INTO vehicle_daily_mileage_source`).
+		WithArgs(
+			"LA9GG64L7PBAF4001",
+			"2026-07-08",
+			"JT808",
+			"JT808:13307765812@115.231.168.135",
+			"115.231.168.135",
+			"115.231.168.135:20215",
+			"13307765812",
+			"",
+			"",
+			float64(4100.8),
+			float64(4136.8),
+			approxFloat64{want: 36.0, tolerance: 0.000001},
+			int64(1),
+			firstTime,
+			currentTime,
+			QualityOK,
+			"same_source_previous_day",
+		).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+	mock.ExpectExec(`UPDATE vehicle_daily_mileage_source`).
+		WithArgs("LA9GG64L7PBAF4001", "2026-07-08", "JT808").
+		WillReturnResult(sqlmock.NewResult(0, 0))
+	mock.ExpectExec(`INSERT INTO vehicle_daily_mileage`).
+		WithArgs("LA9GG64L7PBAF4001", "2026-07-08", "JT808", int64(1000)).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+	mock.ExpectExec(`UPDATE vehicle_daily_mileage_source s`).
+		WithArgs(
+			"LA9GG64L7PBAF4001",
+			"2026-07-08",
+			"JT808",
+			int64(1000),
+			"LA9GG64L7PBAF4001",
+			"2026-07-08",
+			"JT808",
+		).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+	mock.ExpectExec(`DELETE FROM vehicle_daily_mileage`).
+		WithArgs(
+			"LA9GG64L7PBAF4001",
+			"2026-07-08",
+			"JT808",
+			"LA9GG64L7PBAF4001",
+			"2026-07-08",
+			"JT808",
+		).
+		WillReturnResult(sqlmock.NewResult(0, 0))
+
+	if err := writer.Append(context.Background(), event); err != nil {
+		t.Fatalf("Append() error = %v", err)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Fatalf("sql expectations: %v", err)
+	}
+}
+
 func TestWriterEnsuresSchemaAndUpsertsDailyMileage(t *testing.T) {
 	exec := &recordingExec{}
 	writer := NewWriter(exec, time.FixedZone("Asia/Shanghai", 8*3600))

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

@@ -318,6 +318,35 @@ func lookupPreviousSourceBaseline(ctx context.Context, query Queryer, vin string
 	}, latestTotal.Valid, nil
 }
 
+func lookupCurrentSourceBaseline(ctx context.Context, query Queryer, vin string, statDate string, protocol envelope.Protocol, sourceKey string) (sourceBaseline, bool, error) {
+	if query == nil || strings.TrimSpace(vin) == "" || strings.TrimSpace(statDate) == "" || strings.TrimSpace(sourceKey) == "" {
+		return sourceBaseline{}, false, nil
+	}
+	rows, err := query.QueryContext(ctx, currentSourceBaselineSQL, vin, statDate, string(protocol), sourceKey)
+	if err != nil {
+		return sourceBaseline{}, false, err
+	}
+	defer rows.Close()
+	if !rows.Next() {
+		if err := rows.Err(); err != nil {
+			return sourceBaseline{}, false, err
+		}
+		return sourceBaseline{}, false, nil
+	}
+	var firstTotal sql.NullFloat64
+	var firstEvent sql.NullTime
+	if err := rows.Scan(&firstTotal, &firstEvent); err != nil {
+		return sourceBaseline{}, false, err
+	}
+	if err := rows.Err(); err != nil {
+		return sourceBaseline{}, false, err
+	}
+	return sourceBaseline{
+		LatestTotalKM:   firstTotal.Float64,
+		LatestEventTime: firstEvent.Time,
+	}, firstTotal.Valid, nil
+}
+
 func previousStatDate(statDate string) (string, bool) {
 	day, err := time.Parse("2006-01-02", strings.TrimSpace(statDate))
 	if err != nil {
@@ -336,3 +365,15 @@ WHERE vin = ?
 ORDER BY latest_event_time DESC
 LIMIT 1
 `
+
+const currentSourceBaselineSQL = `
+SELECT first_total_mileage_km, first_event_time
+FROM vehicle_daily_mileage_source
+WHERE vin = ?
+  AND stat_date = ?
+  AND protocol = ?
+  AND source_key = ?
+  AND quality_status = '` + QualityOK + `'
+ORDER BY latest_event_time DESC
+LIMIT 1
+`