feat(store): detect overlapping maintenance windows

Warn via log when creating a maintenance window that overlaps with an
existing one for the same monitor, parent group, or global scope.
Handles both timed and indefinite windows.

internal/store/sqlstore.go

@@ -652,6 +652,48 @@ func (s *SQLStore) GetAllMaintenanceWindows(ctx context.Context, limit int) ([]m
 	return windows, rows.Err()
 }
 
+func (s *SQLStore) GetOverlappingMaintenanceWindows(ctx context.Context, monitorID int, startTime, endTime time.Time) ([]models.MaintenanceWindow, error) {
+	var timeClause string
+	var args []interface{}
+
+	if endTime.IsZero() {
+		timeClause = "(end_time IS NULL OR end_time > ?)"
+		args = append(args, startTime)
+	} else {
+		timeClause = "(end_time IS NULL OR end_time > ?) AND start_time < ?"
+		args = append(args, startTime, endTime)
+	}
+
+	var scopeClause string
+	if monitorID == 0 {
+		scopeClause = "1=1"
+	} else {
+		scopeClause = "(monitor_id = ? OR monitor_id = 0 OR monitor_id IN (SELECT parent_id FROM sites WHERE id = ? AND parent_id > 0))"
+		args = append(args, monitorID, monitorID)
+	}
+
+	query := fmt.Sprintf(
+		"SELECT id, monitor_id, title, description, type, start_time, end_time, created_by, created_at FROM maintenance_windows WHERE %s AND %s ORDER BY start_time",
+		timeClause, scopeClause,
+	)
+
+	rows, err := s.db.QueryContext(ctx, s.q(query), args...)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var windows []models.MaintenanceWindow
+	for rows.Next() {
+		mw, err := s.scanMaintenanceWindow(rows)
+		if err != nil {
+			return nil, err
+		}
+		windows = append(windows, mw)
+	}
+	return windows, rows.Err()
+}
+
 func (s *SQLStore) AddMaintenanceWindow(ctx context.Context, mw models.MaintenanceWindow) error {
 	if mw.StartTime.IsZero() {
 		mw.StartTime = time.Now()

internal/store/sqlstore_test.go

@@ -509,6 +509,103 @@ func TestPruneExpiredMaintenanceWindows(t *testing.T) {
 	}
 }
 
+func TestGetOverlappingMaintenanceWindows(t *testing.T) {
+	s := newTestStore(t)
+	ctx := context.Background()
+
+	site := models.SiteConfig{Name: "web", URL: "https://example.com", Interval: 30}
+	if err := s.AddSite(ctx, site); err != nil {
+		t.Fatalf("AddSite: %v", err)
+	}
+
+	now := time.Now()
+
+	active := models.MaintenanceWindow{
+		MonitorID: 1,
+		Title:     "Deploy v2",
+		Type:      "maintenance",
+		StartTime: now.Add(-30 * time.Minute),
+		EndTime:   now.Add(30 * time.Minute),
+	}
+	if err := s.AddMaintenanceWindow(ctx, active); err != nil {
+		t.Fatalf("AddMaintenanceWindow: %v", err)
+	}
+
+	ended := models.MaintenanceWindow{
+		MonitorID: 1,
+		Title:     "Old deploy",
+		Type:      "maintenance",
+		StartTime: now.Add(-3 * time.Hour),
+		EndTime:   now.Add(-2 * time.Hour),
+	}
+	if err := s.AddMaintenanceWindow(ctx, ended); err != nil {
+		t.Fatalf("AddMaintenanceWindow: %v", err)
+	}
+
+	t.Run("same monitor overlaps", func(t *testing.T) {
+		overlaps, err := s.GetOverlappingMaintenanceWindows(ctx, 1, now, now.Add(1*time.Hour))
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if len(overlaps) != 1 {
+			t.Fatalf("expected 1 overlap, got %d", len(overlaps))
+		}
+		if overlaps[0].Title != "Deploy v2" {
+			t.Errorf("expected 'Deploy v2', got %q", overlaps[0].Title)
+		}
+	})
+
+	t.Run("different monitor no overlap", func(t *testing.T) {
+		overlaps, err := s.GetOverlappingMaintenanceWindows(ctx, 99, now, now.Add(1*time.Hour))
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if len(overlaps) != 0 {
+			t.Errorf("expected 0 overlaps, got %d", len(overlaps))
+		}
+	})
+
+	t.Run("global window overlaps all", func(t *testing.T) {
+		global := models.MaintenanceWindow{
+			MonitorID: 0,
+			Title:     "Global freeze",
+			Type:      "maintenance",
+			StartTime: now.Add(-10 * time.Minute),
+			EndTime:   now.Add(2 * time.Hour),
+		}
+		if err := s.AddMaintenanceWindow(ctx, global); err != nil {
+			t.Fatalf("AddMaintenanceWindow: %v", err)
+		}
+		overlaps, err := s.GetOverlappingMaintenanceWindows(ctx, 1, now, now.Add(1*time.Hour))
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if len(overlaps) != 2 {
+			t.Errorf("expected 2 overlaps (specific + global), got %d", len(overlaps))
+		}
+	})
+
+	t.Run("indefinite window overlaps", func(t *testing.T) {
+		overlaps, err := s.GetOverlappingMaintenanceWindows(ctx, 1, now, time.Time{})
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if len(overlaps) < 1 {
+			t.Error("expected at least 1 overlap for indefinite window")
+		}
+	})
+
+	t.Run("ended window excluded", func(t *testing.T) {
+		overlaps, err := s.GetOverlappingMaintenanceWindows(ctx, 1, now.Add(-4*time.Hour), now.Add(-3*time.Hour))
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if len(overlaps) != 0 {
+			t.Errorf("expected 0 overlaps for past range, got %d", len(overlaps))
+		}
+	})
+}
+
 // ImportData must encrypt alert settings (like AddAlert/UpdateAlert) so a
 // restore with UPTOP_ENCRYPTION_KEY set never lands secrets in plaintext.
 func TestImportData_EncryptsAlertSettings(t *testing.T) {

internal/store/store.go

@@ -67,6 +67,7 @@ type Store interface {
 	// Maintenance Windows
 	GetActiveMaintenanceWindows(ctx context.Context) ([]models.MaintenanceWindow, error)
 	GetAllMaintenanceWindows(ctx context.Context, limit int) ([]models.MaintenanceWindow, error)
+	GetOverlappingMaintenanceWindows(ctx context.Context, monitorID int, startTime, endTime time.Time) ([]models.MaintenanceWindow, error)
 	AddMaintenanceWindow(ctx context.Context, mw models.MaintenanceWindow) error
 	EndMaintenanceWindow(ctx context.Context, id int) error
 	DeleteMaintenanceWindow(ctx context.Context, id int) error

internal/store/storetest/mock.go

@@ -229,6 +229,10 @@ func (m *BaseMock) GetAllMaintenanceWindows(ctx context.Context, limit int) ([]m
 	return nil, nil
 }
 
+func (m *BaseMock) GetOverlappingMaintenanceWindows(_ context.Context, _ int, _, _ time.Time) ([]models.MaintenanceWindow, error) {
+	return nil, nil
+}
+
 func (m *BaseMock) AddMaintenanceWindow(_ context.Context, _ models.MaintenanceWindow) error {
 	return nil
 }

internal/tui/tab_maint.go

@@ -256,6 +256,11 @@ func (m *Model) submitMaintForm() tea.Cmd {
 	st := m.store
 	m.state = stateDashboard
 	return writeCmd("Add maintenance window", func() error {
-		return st.AddMaintenanceWindow(context.Background(), mw)
+		ctx := context.Background()
+		overlaps, _ := st.GetOverlappingMaintenanceWindows(ctx, mw.MonitorID, mw.StartTime, mw.EndTime)
+		if len(overlaps) > 0 {
+			_ = st.SaveLog(ctx, fmt.Sprintf("Overlap: new window %q overlaps with existing %q", mw.Title, overlaps[0].Title))
+		}
+		return st.AddMaintenanceWindow(ctx, mw)
 	})
 }