func (l Lister) ListDatacenter(ctx context.Context) ([]Element, error) {
	ospec := types.ObjectSpec{
		Obj:  l.Reference,
		Skip: types.NewBool(true),
	}

	// Include every datastore folder in the select set
	fields := []string{
		"vmFolder",
		"hostFolder",
		"datastoreFolder",
		"networkFolder",
	}

	for _, f := range fields {
		tspec := types.TraversalSpec{
			Path: f,
			Skip: types.NewBool(false),
			Type: "Datacenter",
		}

		ospec.SelectSet = append(ospec.SelectSet, &tspec)
	}

	pspec := types.PropertySpec{
		Type: "Folder",
	}

	if l.All {
		pspec.All = types.NewBool(true)
	} else {
		pspec.PathSet = []string{"name"}
	}

	req := types.RetrieveProperties{
		SpecSet: []types.PropertyFilterSpec{
			{
				ObjectSet: []types.ObjectSpec{ospec},
				PropSet:   []types.PropertySpec{pspec},
			},
		},
	}

	var dst []interface{}

	err := l.retrieveProperties(ctx, req, &dst)
	if err != nil {
		return nil, err
	}

	es := []Element{}
	for _, v := range dst {
		es = append(es, ToElement(v.(mo.Reference), l.Prefix))
	}

	return es, nil
}

// Retrieve loads properties for a slice of managed objects. The dst argument
// must be a pointer to a []interface{}, which is populated with the instances
// of the specified managed objects, with the relevant properties filled in. If
// the properties slice is nil, all properties are loaded.
func (p *Collector) Retrieve(ctx context.Context, objs []types.ManagedObjectReference, ps []string, dst interface{}) error {
	var propSpec *types.PropertySpec
	var objectSet []types.ObjectSpec

	for _, obj := range objs {
		// Ensure that all object reference types are the same
		if propSpec == nil {
			propSpec = &types.PropertySpec{
				Type: obj.Type,
			}

			if ps == nil {
				propSpec.All = types.NewBool(true)
			} else {
				propSpec.PathSet = ps
			}
		} else {
			if obj.Type != propSpec.Type {
				return errors.New("object references must have the same type")
			}
		}

		objectSpec := types.ObjectSpec{
			Obj:  obj,
			Skip: types.NewBool(false),
		}

		objectSet = append(objectSet, objectSpec)
	}

	req := types.RetrieveProperties{
		SpecSet: []types.PropertyFilterSpec{
			{
				ObjectSet: objectSet,
				PropSet:   []types.PropertySpec{*propSpec},
			},
		},
	}

	res, err := p.RetrieveProperties(ctx, req)
	if err != nil {
		return err
	}

	return mo.LoadRetrievePropertiesResponse(res, dst)
}

func (l Lister) ListVirtualApp(ctx context.Context) ([]Element, error) {
	ospec := types.ObjectSpec{
		Obj:  l.Reference,
		Skip: types.NewBool(true),
	}

	fields := []string{
		"resourcePool",
		"vm",
	}

	for _, f := range fields {
		tspec := types.TraversalSpec{
			Path: f,
			Skip: types.NewBool(false),
			Type: "VirtualApp",
		}

		ospec.SelectSet = append(ospec.SelectSet, &tspec)
	}

	childTypes := []string{
		"ResourcePool",
		"VirtualMachine",
	}

	var pspecs []types.PropertySpec
	for _, t := range childTypes {
		pspec := types.PropertySpec{
			Type: t,
		}

		if l.All {
			pspec.All = types.NewBool(true)
		} else {
			pspec.PathSet = []string{"name"}
		}

		pspecs = append(pspecs, pspec)
	}

	req := types.RetrieveProperties{
		SpecSet: []types.PropertyFilterSpec{
			{
				ObjectSet: []types.ObjectSpec{ospec},
				PropSet:   pspecs,
			},
		},
	}

	var dst []interface{}

	err := l.retrieveProperties(ctx, req, &dst)
	if err != nil {
		return nil, err
	}

	es := []Element{}
	for _, v := range dst {
		es = append(es, ToElement(v.(mo.Reference), l.Prefix))
	}

	return es, nil
}

func (l Lister) ListFolder(ctx context.Context) ([]Element, error) {
	spec := types.PropertyFilterSpec{
		ObjectSet: []types.ObjectSpec{
			{
				Obj: l.Reference,
				SelectSet: []types.BaseSelectionSpec{
					&types.TraversalSpec{
						Path: "childEntity",
						Skip: types.NewBool(false),
						Type: "Folder",
					},
				},
				Skip: types.NewBool(true),
			},
		},
	}

	// Retrieve all objects that we can deal with
	childTypes := []string{
		"Folder",
		"Datacenter",
		"VirtualApp",
		"VirtualMachine",
		"Network",
		"ComputeResource",
		"ClusterComputeResource",
		"Datastore",
		"DistributedVirtualSwitch",
	}

	for _, t := range childTypes {
		pspec := types.PropertySpec{
			Type: t,
		}

		if l.All {
			pspec.All = types.NewBool(true)
		} else {
			pspec.PathSet = []string{"name"}

			// Additional basic properties.
			switch t {
			case "ComputeResource", "ClusterComputeResource":
				// The ComputeResource and ClusterComputeResource are dereferenced in
				// the ResourcePoolFlag. Make sure they always have their resourcePool
				// field populated.
				pspec.PathSet = append(pspec.PathSet, "resourcePool")
			}
		}

		spec.PropSet = append(spec.PropSet, pspec)
	}

	req := types.RetrieveProperties{
		SpecSet: []types.PropertyFilterSpec{spec},
	}

	var dst []interface{}

	err := l.retrieveProperties(ctx, req, &dst)
	if err != nil {
		return nil, err
	}

	es := []Element{}
	for _, v := range dst {
		es = append(es, ToElement(v.(mo.Reference), l.Prefix))
	}

	return es, nil
}