From 46f0d373ce7bf532387d02adfe77e79b4f04d8c6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Miloslav=20Trma=C4=8D?= <mitr@redhat.com>
Date: Tue, 10 Sep 2024 20:31:53 +0200
Subject: [PATCH] Add oci/layout.List
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The new API allows for listing all manifests in an OCI layout's index.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>
Signed-off-by: Valentin Rothberg <vrothberg@redhat.com>
---
 oci/layout/reader.go      | 52 ++++++++++++++++++++++++++++++
 oci/layout/reader_test.go | 68 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 120 insertions(+)
 create mode 100644 oci/layout/reader.go
 create mode 100644 oci/layout/reader_test.go

diff --git a/oci/layout/reader.go b/oci/layout/reader.go
new file mode 100644
index 0000000000..078ef68615
--- /dev/null
+++ b/oci/layout/reader.go
@@ -0,0 +1,52 @@
+package layout
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/containers/image/v5/types"
+	imgspecv1 "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+// This file is named reader.go for consistency with other transports
+// handling of “image containers”, but we don’t  actually need a stateful reader object.
+
+// ListResult wraps the image reference and the manifest for loading
+type ListResult struct {
+	Reference          types.ImageReference
+	ManifestDescriptor imgspecv1.Descriptor
+}
+
+// List returns a slice of manifests included in the archive
+func List(dir string) ([]ListResult, error) {
+	var res []ListResult
+
+	indexJSON, err := os.ReadFile(filepath.Join(dir, imgspecv1.ImageIndexFile))
+	if err != nil {
+		return nil, err
+	}
+	var index imgspecv1.Index
+	if err := json.Unmarshal(indexJSON, &index); err != nil {
+		return nil, err
+	}
+
+	for manifestIndex, md := range index.Manifests {
+		refName := md.Annotations[imgspecv1.AnnotationRefName]
+		index := -1
+		if refName == "" {
+			index = manifestIndex
+		}
+		ref, err := newReference(dir, refName, index)
+		if err != nil {
+			return nil, fmt.Errorf("error creating image reference: %w", err)
+		}
+		reference := ListResult{
+			Reference:          ref,
+			ManifestDescriptor: md,
+		}
+		res = append(res, reference)
+	}
+	return res, nil
+}
diff --git a/oci/layout/reader_test.go b/oci/layout/reader_test.go
new file mode 100644
index 0000000000..ebfe916d50
--- /dev/null
+++ b/oci/layout/reader_test.go
@@ -0,0 +1,68 @@
+package layout
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestList(t *testing.T) {
+
+	for _, test := range []struct {
+		path    string
+		num     int
+		digests []string
+		names   map[int]string
+	}{
+		{
+			path: "fixtures/two_images_manifest",
+			num:  2,
+			digests: []string{
+				"sha256:e692418e4cbaf90ca69d05a66403747baa33ee08806650b51fab815ad7fc331f",
+				"sha256:5b0bcabd1ed22e9fb1310cf6c2dec7cdef19f0ad69efa1f392e94a4333501270",
+			},
+			names: map[int]string{0: "", 1: ""},
+		},
+		{
+			path: "fixtures/manifest",
+			num:  1,
+			digests: []string{
+				"sha256:84afb6189c4d69f2d040c5f1dc4e0a16fed9b539ce9cfb4ac2526ae4e0576cc0",
+			},
+			names: map[int]string{0: "v0.1.1"},
+		},
+		{
+			path: "fixtures/name_lookups",
+			num:  4,
+			digests: []string{
+				"sha256:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+				"sha256:bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
+				"sha256:cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc",
+				"sha256:dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd",
+			},
+			names: map[int]string{0: "a", 1: "b", 2: "invalid-mime", 3: "invalid-mime"},
+		},
+	} {
+		results, err := List(test.path)
+		require.NoError(t, err)
+		require.NotNil(t, results)
+		require.Len(t, results, test.num)
+		for i, res := range results {
+			ociRef, ok := res.Reference.(ociReference)
+			require.True(t, ok)
+			require.Equal(t, test.digests[i], res.ManifestDescriptor.Digest.String())
+			require.Equal(t, test.names[i], ociRef.image)
+			if test.names[i] != "" {
+				require.True(t, strings.HasSuffix(res.Reference.StringWithinTransport(), test.names[i]))
+			}
+			_, err := ParseReference(fmt.Sprintf("%s:@%d", test.path, i))
+			require.NoError(t, err)
+		}
+	}
+
+	results, err := List("fixtures/i_do_not_exist")
+	require.Error(t, err)
+	require.Nil(t, results)
+}