Merge pull request #39 from glyn/add-client-interface-back

Reinstate Client interface

pkg/registry/client.go

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2019-Present Pivotal Software, Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package registry
+
+import (
+	"github.com/pivotal/image-relocation/pkg/image"
+)
+
+// Client provides a way of interacting with image registries.
+type Client interface {
+	// Digest returns the digest of the given image or an error if the image does not exist or the digest is unavailable.
+	Digest(image.Name) (image.Digest, error)
+
+	// Copy copies the given source image to the given target and returns the image's digest (which is preserved) and
+	// the size in bytes of the raw image manifest.
+	Copy(source image.Name, target image.Name) (image.Digest, int64, error)
+
+	// NewLayout creates a Layout for the Client and creates a corresponding directory containing a new OCI image layout at
+	// the given file system path.
+	NewLayout(path string) (Layout, error)
+
+	// ReadLayout creates a Layout for the Client from the given file system path of a directory containing an existing
+	// OCI image layout.
+	ReadLayout(path string) (Layout, error)
+}

pkg/registry/ggcr/client.go

@@ -31,6 +31,7 @@ import (
 const outputDirPermissions = 0755
 
 // RegistryClient provides methods for building abstract images.
+// This interface is not intended for external consumption.
 type RegistryClient interface {
 	// ReadRemoteImage builds an abstract image from a repository.
 	ReadRemoteImage(n image.Name) (registry.Image, error)
@@ -51,7 +52,11 @@ type client struct {
 	writeRemoteIndex indexWriter
 }
 
-var _ RegistryClient = &client{}
+var (
+	// Ensure client conforms to the relevant interfaces.
+	_ RegistryClient = &client{}
+	_ registry.Client = &client{}
+)
 
 // NewRegistryClient returns a new Client.
 func NewRegistryClient() *client {