// Implements storage.Interface.
func (h *etcdHelper) List(key string, listObj runtime.Object) error {
	trace := util.NewTrace("List " + getTypeName(listObj))
	defer trace.LogIfLong(time.Second)
	listPtr, err := runtime.GetItemsPtr(listObj)
	if err != nil {
		return err
	}
	key = h.prefixEtcdKey(key)
	startTime := time.Now()
	trace.Step("About to list etcd node")
	nodes, index, err := h.listEtcdNode(key)
	metrics.RecordEtcdRequestLatency("list", getTypeName(listPtr), startTime)
	trace.Step("Etcd node listed")
	if err != nil {
		return err
	}
	if err := h.decodeNodeList(nodes, listPtr); err != nil {
		return err
	}
	trace.Step("Node list decoded")
	if h.versioner != nil {
		if err := h.versioner.UpdateList(listObj, index); err != nil {
			return err
		}
	}
	return nil
}

// Implements storage.Interface.
func (h *etcdHelper) GetToList(key string, listObj runtime.Object) error {
	trace := util.NewTrace("GetToList " + getTypeName(listObj))
	listPtr, err := runtime.GetItemsPtr(listObj)
	if err != nil {
		return err
	}
	key = h.prefixEtcdKey(key)
	startTime := time.Now()
	trace.Step("About to read etcd node")
	response, err := h.client.Get(key, false, false)
	metrics.RecordEtcdRequestLatency("get", getTypeName(listPtr), startTime)
	trace.Step("Etcd node read")
	if err != nil {
		if IsEtcdNotFound(err) {
			return nil
		}
		return err
	}

	nodes := make([]*etcd.Node, 0)
	nodes = append(nodes, response.Node)

	if err := h.decodeNodeList(nodes, listPtr); err != nil {
		return err
	}
	trace.Step("Object decoded")
	if h.versioner != nil {
		if err := h.versioner.UpdateList(listObj, response.EtcdIndex); err != nil {
			return err
		}
	}
	return nil
}

// ExtractObjToList unmarshals json found at key and opaques it into a *List api object
// (an object that satisfies the runtime.IsList definition).
func (h *EtcdHelper) ExtractObjToList(key string, listObj runtime.Object) error {
	listPtr, err := runtime.GetItemsPtr(listObj)
	if err != nil {
		return err
	}

	response, err := h.Client.Get(key, false, false)
	if err != nil {
		if IsEtcdNotFound(err) {
			return nil
		}
		return err
	}

	nodes := make([]*etcd.Node, 0)
	nodes = append(nodes, response.Node)

	if err := h.decodeNodeList(nodes, listPtr); err != nil {
		return err
	}
	if h.Versioner != nil {
		if err := h.Versioner.UpdateList(listObj, response.EtcdIndex); err != nil {
			return err
		}
	}
	return nil
}

// ExtractToList is just like ExtractList, but it works on a ThingyList api object.
// extracts a go object per etcd node into a slice with the resource version.
func (h *EtcdHelper) ExtractToList(key string, listObj runtime.Object) error {
	var resourceVersion uint64
	listPtr, err := runtime.GetItemsPtr(listObj)
	if err != nil {
		return err
	}
	if err := h.ExtractList(key, listPtr, &resourceVersion); err != nil {
		return err
	}
	if h.ResourceVersioner != nil {
		if err := h.ResourceVersioner.SetResourceVersion(listObj, resourceVersion); err != nil {
			return err
		}
	}
	return nil
}

// ExtractToList works on a *List api object (an object that satisfies the runtime.IsList
// definition) and extracts a go object per etcd node into a slice with the resource version.
func (h *EtcdHelper) ExtractToList(key string, listObj runtime.Object) error {
	listPtr, err := runtime.GetItemsPtr(listObj)
	if err != nil {
		return err
	}
	nodes, index, err := h.listEtcdNode(key)
	if err != nil {
		return err
	}
	if err := h.decodeNodeList(nodes, listPtr); err != nil {
		return err
	}
	if h.Versioner != nil {
		if err := h.Versioner.UpdateList(listObj, index); err != nil {
			return err
		}
	}
	return nil
}

// Object returns a single object representing the output of a single visit to all
// found resources.  If the Builder was a singular context (expected to return a
// single resource by user input) and only a single resource was found, the resource
// will be returned as is.  Otherwise, the returned resources will be part of an
// api.List. The ResourceVersion of the api.List will be set only if it is identical
// across all infos returned.
func (r *Result) Object() (runtime.Object, error) {
	infos, err := r.Infos()
	if err != nil {
		return nil, err
	}

	versions := util.StringSet{}
	objects := []runtime.Object{}
	for _, info := range infos {
		if info.Object != nil {
			objects = append(objects, info.Object)
			versions.Insert(info.ResourceVersion)
		}
	}

	if len(objects) == 1 {
		if r.singular {
			return objects[0], nil
		}
		// if the item is a list already, don't create another list
		if _, err := runtime.GetItemsPtr(objects[0]); err == nil {
			return objects[0], nil
		}
	}

	version := ""
	if len(versions) == 1 {
		version = versions.List()[0]
	}
	return &api.List{
		ListMeta: api.ListMeta{
			ResourceVersion: version,
		},
		Items: objects,
	}, err
}