update(pkg/oci): remove the need for artifact type in pull

also, allow to specify no tag when pulling.
the default one will be used in this case (latest), exactly the same as in the push command.

Signed-off-by: Lorenzo Susini <[email protected]>

Author: loresuso

pkg/oci/puller/puller.go

@@ -16,7 +16,9 @@ package puller
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
+	"io"
 
 	v1 "github.com/opencontainers/image-spec/specs-go/v1"
 	"oras.land/oras-go/v2"
@@ -47,7 +49,7 @@ func NewPuller(client *auth.Client, tracker ProgressTracker) *Puller {
 
 // Pull an artifact from a remote registry.
 // Ref format follows: REGISTRY/REPO[:TAG|@DIGEST]. Ex. localhost:5000/hello:latest.
-func (p *Puller) Pull(ctx context.Context, artifactType oci.ArtifactType, ref, destDir, os, arch string) (*oci.RegistryResult, error) {
+func (p *Puller) Pull(ctx context.Context, ref, destDir, os, arch string) (*oci.RegistryResult, error) {
 	fileStore := file.New(destDir)
 
 	repo, err := remote.NewRepository(ref)
@@ -56,14 +58,20 @@ func (p *Puller) Pull(ctx context.Context, artifactType oci.ArtifactType, ref, d
 	}
 	repo.Client = p.Client
 
+	// if no tag was specified, "latest" is used
+	if repo.Reference.Reference == "" {
+		ref += ":" + oci.DefaultTag
+		repo.Reference.Reference = oci.DefaultTag
+	}
+
 	refDesc, _, err := repo.FetchReference(ctx, ref)
 	if err != nil {
 		return nil, err
 	}
 
 	copyOpts := oras.CopyOptions{}
 	copyOpts.Concurrency = 1
-	if artifactType == oci.Plugin && refDesc.MediaType == v1.MediaTypeImageIndex {
+	if refDesc.MediaType == v1.MediaTypeImageIndex {
 		plt := &v1.Platform{
 			OS:           os,
 			Architecture: arch,
@@ -83,7 +91,37 @@ func (p *Puller) Pull(ctx context.Context, artifactType oci.ArtifactType, ref, d
 			repo.Reference.Repository, repo.Reference.Reference, repo.Reference.Repository, err)
 	}
 
+	descReader, err := repo.Fetch(ctx, desc)
+	if err != nil {
+		return nil, fmt.Errorf("unable to fetch descriptor with digest %q: %w", desc.Digest, err)
+	}
+
+	var manifest v1.Manifest
+	descBytes, err := io.ReadAll(descReader)
+	if err != nil {
+		return nil, fmt.Errorf("unable to read bytes from descriptor: %w", err)
+	}
+
+	if err = json.Unmarshal(descBytes, &manifest); err != nil {
+		return nil, fmt.Errorf("unable to unmarshal manifest: %w", err)
+	}
+
+	if len(manifest.Layers) < 1 {
+		return nil, fmt.Errorf("no layers in manifest")
+	}
+
+	var artifactType oci.ArtifactType
+	switch manifest.Layers[0].MediaType {
+	case oci.FalcoPluginLayerMediaType:
+		artifactType = oci.Plugin
+	case oci.FalcoRulesfileLayerMediaType:
+		artifactType = oci.Rulesfile
+	default:
+		return nil, fmt.Errorf("unknown media type: %q", manifest.Layers[0].MediaType)
+	}
+
 	return &oci.RegistryResult{
 		Digest: string(desc.Digest),
+		Type:   artifactType,
 	}, nil
 }