fix(stats): flush throttled daily mileage projections

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

@@ -797,6 +797,97 @@ func TestWriterAppendThrottlesDailyProjectionPerVehicleProtocolDate(t *testing.T
 	}
 }
 
+func TestWriterFlushesFinalProjectionWhenVehicleStopsInsideThrottleWindow(t *testing.T) {
+	exec := &recordingExec{}
+	loc := time.FixedZone("Asia/Shanghai", 8*3600)
+	writer := NewWriter(exec, loc)
+	base := managedTestSource(envelope.FrameEnvelope{
+		Protocol:       envelope.ProtocolJT808,
+		VIN:            "LMRKH9AC7R1004120",
+		Phone:          "64341233712",
+		SourceEndpoint: "115.159.85.149:7339",
+		Fields: map[string]any{
+			"jt808.location.total_mileage_km": 4732.6,
+		},
+	})
+
+	first := base
+	first.EventTimeMS = time.Date(2026, 7, 19, 15, 4, 45, 0, loc).UnixMilli()
+	if err := writer.Append(context.Background(), first); err != nil {
+		t.Fatalf("first Append() error = %v", err)
+	}
+	final := base
+	final.EventTimeMS = time.Date(2026, 7, 19, 15, 4, 52, 0, loc).UnixMilli()
+	final.Fields = map[string]any{"jt808.location.total_mileage_km": 4740.7}
+	if err := writer.Append(context.Background(), final); err != nil {
+		t.Fatalf("final Append() error = %v", err)
+	}
+
+	if got := writer.CacheStats().PendingProjectionEntries; got != 1 {
+		t.Fatalf("pending projections = %d, want final throttled sample queued", got)
+	}
+	beforeDue, err := writer.FlushPendingProjections(context.Background(), time.Now().Add(-time.Hour))
+	if err != nil {
+		t.Fatalf("early FlushPendingProjections() error = %v", err)
+	}
+	if beforeDue.Attempted != 0 || beforeDue.Written != 0 {
+		t.Fatalf("early flush result = %+v, want no eligible projection", beforeDue)
+	}
+
+	flushed, err := writer.FlushPendingProjections(context.Background(), time.Time{})
+	if err != nil {
+		t.Fatalf("FlushPendingProjections() error = %v", err)
+	}
+	if flushed.Attempted != 1 || flushed.Written != 1 {
+		t.Fatalf("flush result = %+v, want final projection written", flushed)
+	}
+	if got := countExecQueries(exec.calls, "INSERT INTO vehicle_daily_mileage\n"); got != 2 {
+		t.Fatalf("daily projections = %d, want initial plus eventual final projection", got)
+	}
+	if got := writer.CacheStats().PendingProjectionEntries; got != 0 {
+		t.Fatalf("pending projections after flush = %d, want 0", got)
+	}
+	key := projectionCacheKey(MetricSample{
+		VIN:      "LMRKH9AC7R1004120",
+		Protocol: envelope.ProtocolJT808,
+		StatDate: "2026-07-19",
+	})
+	wantProjectedAt := time.UnixMilli(final.EventTimeMS).In(loc)
+	if got := writer.lastProjection[key].projectedAt; !got.Equal(wantProjectedAt) {
+		t.Fatalf("last projected event = %s, want %s", got, wantProjectedAt)
+	}
+}
+
+func TestWriterPendingProjectionFailureDoesNotBlockOtherVehicles(t *testing.T) {
+	exec := &selectiveFailingExec{failVIN: "FAIL-VIN"}
+	loc := time.FixedZone("Asia/Shanghai", 8*3600)
+	writer := NewWriter(exec, loc)
+	writer.projectionInterval = time.Hour
+
+	for _, vin := range []string{"FAIL-VIN", "OK-VIN"} {
+		sample := MetricSample{
+			VIN:            vin,
+			Protocol:       envelope.ProtocolJT808,
+			StatDate:       "2026-07-19",
+			SourceKey:      "jt808:test",
+			EventTime:      time.Date(2026, 7, 19, 15, 4, 52, 0, loc),
+			TotalMileageKM: 100,
+		}
+		writer.markProjectionPending(sample, time.Now().Add(-time.Hour))
+	}
+
+	result, err := writer.FlushPendingProjections(context.Background(), time.Time{})
+	if err == nil {
+		t.Fatal("FlushPendingProjections() error = nil, want failed vehicle reported")
+	}
+	if result.Attempted != 2 || result.Written != 1 || result.Failed != 1 {
+		t.Fatalf("flush result = %+v, want one failure and one successful projection", result)
+	}
+	if got := writer.CacheStats().PendingProjectionEntries; got != 1 {
+		t.Fatalf("pending projections after partial failure = %d, want only failed vehicle retained", got)
+	}
+}
+
 func TestWriterAppendProjectsImmediatelyForNewSource(t *testing.T) {
 	exec := &recordingExec{}
 	loc := time.FixedZone("Asia/Shanghai", 8*3600)
@@ -2321,6 +2412,17 @@ type recordingExec struct {
 	errs  []error
 }
 
+type selectiveFailingExec struct {
+	failVIN string
+}
+
+func (e *selectiveFailingExec) ExecContext(_ context.Context, _ string, args ...any) (sql.Result, error) {
+	if len(args) > 0 && fmt.Sprint(args[0]) == e.failVIN {
+		return nil, errors.New("test projection failure")
+	}
+	return nil, nil
+}
+
 type concurrentExec struct {
 	mu    sync.Mutex
 	calls int