refactor: add resolve metadata handler

cmd/oras/internal/display/handler.go

@@ -235,3 +235,8 @@ func NewBlobPushHandler(printer *output.Printer, outputDescriptor bool, pretty b
 	}
 	return status.NewTextBlobPushHandler(printer, desc), text.NewBlobPushHandler(printer, desc)
 }
+
+// NewResolveHandler returns a resolve metadata handler.
+func NewResolveHandler(printer *output.Printer, fullRef bool, path string) metadata.ResolveHandler {
+	return text.NewResolveHandler(printer, fullRef, path)
+}

cmd/oras/internal/display/metadata/interface.go

@@ -115,3 +115,8 @@ type BlobPushHandler interface {
 
 	OnBlobPushed(target *option.Target) error
 }
+
+// ResolveHandler handles metadata output for resolve events.
+type ResolveHandler interface {
+	OnResolved(desc ocispec.Descriptor) error
+}

cmd/oras/internal/display/metadata/text/resolve.go

@@ -0,0 +1,46 @@
+/*
+Copyright The ORAS Authors.
+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 text
+
+import (
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+	"oras.land/oras/cmd/oras/internal/display/metadata"
+	"oras.land/oras/cmd/oras/internal/output"
+)
+
+// ResolveHandler handles text metadata output for resolve events.
+type ResolveHandler struct {
+	printer *output.Printer
+	fullRef bool
+	path    string
+}
+
+// NewResolveHandler returns a new handler for resolve events.
+func NewResolveHandler(printer *output.Printer, fullRef bool, path string) metadata.ResolveHandler {
+	return &ResolveHandler{
+		printer: printer,
+		fullRef: fullRef,
+		path:    path,
+	}
+}
+
+// OnResolved implements metadata.ResolveHandler.
+func (h *ResolveHandler) OnResolved(desc ocispec.Descriptor) error {
+	if h.fullRef {
+		return h.printer.Printf("%s@%s\n", h.path, desc.Digest)
+	}
+	return h.printer.Println(desc.Digest.String())
+}

cmd/oras/root/resolve.go

@@ -22,6 +22,7 @@ import (
 	"oras.land/oras-go/v2"
 	"oras.land/oras/cmd/oras/internal/argument"
 	"oras.land/oras/cmd/oras/internal/command"
+	"oras.land/oras/cmd/oras/internal/display"
 	oerrors "oras.land/oras/cmd/oras/internal/errors"
 	"oras.land/oras/cmd/oras/internal/option"
 )
@@ -70,19 +71,12 @@ func runResolve(cmd *cobra.Command, opts *resolveOptions) error {
 	if err := opts.EnsureReferenceNotEmpty(cmd, true); err != nil {
 		return err
 	}
+	metadataHandler := display.NewResolveHandler(opts.Printer, opts.fullRef, opts.Path)
 	resolveOpts := oras.DefaultResolveOptions
 	resolveOpts.TargetPlatform = opts.Platform.Platform
 	desc, err := oras.Resolve(ctx, repo, opts.Reference, resolveOpts)
-
 	if err != nil {
 		return fmt.Errorf("failed to resolve digest: %w", err)
 	}
-
-	if opts.fullRef {
-		_ = opts.Printer.Printf("%s@%s\n", opts.Path, desc.Digest)
-	} else {
-		_ = opts.Printer.Println(desc.Digest.String())
-	}
-
-	return nil
+	return metadataHandler.OnResolved(desc)
 }