Add tape view command

README.md

@@ -80,6 +80,7 @@ Tape has the following commands:
 - `tape images` - examine images referenced by a given set of manifests before packaging them
 - `tape package` - package an artifcat and push it to a registry
 - `tape pull` – downlowad and extract contents and attestations from an existing artifact
+- `tape view` – inspect an existing artifact
 
 ### Example
 

tape/app/app.go

@@ -85,6 +85,13 @@ func Run() int {
 				OutputManifestDirOptions: OutputManifestDirOptions{},
 			},
 		},
+		{
+			name:  "view",
+			short: "View an artefact",
+			options: &TapeViewCommand{
+				tape: tape,
+			},
+		},
 	}
 
 	for _, c := range commands {

tape/app/view.go

@@ -0,0 +1,119 @@
+package app
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+
+	"github.com/docker/labs-brown-tape/oci"
+)
+
+type TapeViewCommand struct {
+	tape *TapeCommand
+	OutputFormatOptions
+
+	Image string `short:"I" long:"image" description:"Name of the image to view" required:"true"`
+}
+
+type artefactInfo struct {
+	RawManifests struct {
+		Index   rawManifest[oci.IndexManifest] `json:"index"`
+		Content rawManifest[oci.Manifest]      `json:"content"`
+		Attest  rawManifest[oci.Manifest]      `json:"attest"`
+	} `json:"rawManifests"`
+}
+
+type rawManifest[T oci.Manifest | oci.IndexManifest] struct {
+	Digest   string `json:"digest,omitempty"`
+	Manifest *T     `json:"manifest,omitempty"`
+}
+
+func (c *TapeViewCommand) Execute(args []string) error {
+	ctx := context.WithValue(c.tape.ctx, "command", "view")
+	if len(args) != 0 {
+		return fmt.Errorf("unexpected arguments: %v", args)
+	}
+
+	if err := c.tape.Init(); err != nil {
+		return err
+	}
+
+	client := oci.NewClient(nil)
+
+	outputInfo, err := c.CollectInfo(ctx, client)
+	if err != nil {
+		return fmt.Errorf("failed to collect info about artifact: %w", err)
+	}
+
+	if err := c.PrintInfo(ctx, outputInfo); err != nil {
+		return fmt.Errorf("failed to print info about artifact: %w", err)
+	}
+
+	return nil
+}
+
+func (c *TapeViewCommand) CollectInfo(ctx context.Context, client *oci.Client) (*artefactInfo, error) {
+	artefactInfo := &artefactInfo{}
+
+	imageIndex, indexManifest, _, err := client.GetIndexOrImage(ctx, c.Image)
+	if err != nil {
+		return nil, err
+	}
+	if indexManifest == nil {
+		return nil, fmt.Errorf("no index manifest found for %q", c.Image)
+	}
+
+	imageIndexDigest, err := imageIndex.Digest()
+	if err != nil {
+		return nil, err
+	}
+
+	artefactInfo.RawManifests.Index = rawManifest[oci.IndexManifest]{
+		Digest:   imageIndexDigest.String(),
+		Manifest: indexManifest,
+	}
+
+	imageInfo, manifests, err := client.FetchFromIndexOrImage(ctx, imageIndex, indexManifest, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	if len(imageInfo) == 0 {
+		return nil, fmt.Errorf("no images found in index %q", c.Image)
+	}
+
+	for i := range imageInfo {
+		info := imageInfo[i]
+		switch info.MediaType {
+		case oci.ContentMediaType:
+		case oci.AttestMediaType:
+		}
+	}
+
+	for digest := range manifests {
+		m := rawManifest[oci.Manifest]{
+			Digest:   digest.String(),
+			Manifest: manifests[digest],
+		}
+		switch m.Manifest.Config.MediaType {
+		case oci.ContentMediaType:
+			artefactInfo.RawManifests.Content = m
+		case oci.AttestMediaType:
+			artefactInfo.RawManifests.Attest = m
+		}
+	}
+	return artefactInfo, nil
+}
+
+func (c *TapeViewCommand) PrintInfo(ctx context.Context, outputInfo *artefactInfo) error {
+	stdj := json.NewEncoder(os.Stdout)
+	switch c.OutputFormat {
+	case OutputFormatDirectJSON:
+		stdj.SetIndent("", "  ")
+		if err := stdj.Encode(outputInfo); err != nil {
+			return fmt.Errorf("failed to marshal output: %w", err)
+		}
+	}
+	return nil
+}