images, services/images: implement image service

Server and Client images of the image store are now provided. We have
created an image metadata interface and converted the bolt functions to
implement that interface over an transaction. A remote client
implementation is provided that implements the same interface.

Signed-off-by: Stephen J Day <stephen.day@docker.com>

services/images/client.go

@@ -0,0 +1,60 @@
+package images
+
+import (
+	"context"
+
+	imagesapi "github.com/containerd/containerd/api/services/images"
+	"github.com/containerd/containerd/images"
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+type remoteStore struct {
+	client imagesapi.ImagesClient
+}
+
+func NewStoreFromClient(client imagesapi.ImagesClient) images.Store {
+	return &remoteStore{
+		client: client,
+	}
+}
+
+func (s *remoteStore) Put(ctx context.Context, name string, desc ocispec.Descriptor) error {
+	// TODO(stevvooe): Consider that the remote may want to augment and return
+	// a modified image.
+	_, err := s.client.Put(ctx, &imagesapi.PutRequest{
+		Image: imagesapi.Image{
+			Name:   name,
+			Target: descToProto(&desc),
+		},
+	})
+
+	return rewriteGRPCError(err)
+}
+
+func (s *remoteStore) Get(ctx context.Context, name string) (images.Image, error) {
+	resp, err := s.client.Get(ctx, &imagesapi.GetRequest{
+		Name: name,
+	})
+	if err != nil {
+		return images.Image{}, rewriteGRPCError(err)
+	}
+
+	return imageFromProto(resp.Image), nil
+}
+
+func (s *remoteStore) List(ctx context.Context) ([]images.Image, error) {
+	resp, err := s.client.List(ctx, &imagesapi.ListRequest{})
+	if err != nil {
+		return nil, rewriteGRPCError(err)
+	}
+
+	return imagesFromProto(resp.Images), nil
+}
+
+func (s *remoteStore) Delete(ctx context.Context, name string) error {
+	_, err := s.client.Delete(ctx, &imagesapi.DeleteRequest{
+		Name: name,
+	})
+
+	return rewriteGRPCError(err)
+}