docs: update examples in README.md

pkg/mirror/example_mirror.go

@@ -0,0 +1,150 @@
+package mirror
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/docker/attest/internal/embed"
+	v1 "github.com/google/go-containerregistry/pkg/v1"
+)
+
+type TufMirrorOutput struct {
+	metadata          *v1.Image
+	delegatedMetadata []*MirrorImage
+	targets           []*MirrorImage
+	delegatedTargets  []*MirrorIndex
+}
+
+func ExampleMirror() {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		panic(err)
+	}
+	tufOutputPath := filepath.Join(home, ".docker", "tuf")
+
+	// configure TUF mirror
+	metadataURI := "https://docker.github.io/tuf-staging/metadata"
+	targetsURI := "https://docker.github.io/tuf-staging/targets"
+	m, err := NewTufMirror(embed.DefaultRoot, tufOutputPath, metadataURI, targetsURI)
+	if err != nil {
+		panic(err)
+	}
+
+	// create metadata manifest
+	metadataManifest, err := m.GetMetadataManifest(metadataURI)
+	if err != nil {
+		panic(err)
+	}
+	// create delegated targets metadata manifests
+	delegatedMetadata, err := m.GetDelegatedMetadataMirrors()
+	if err != nil {
+		panic(err)
+	}
+
+	// create targets manifest
+	targets, err := m.GetTufTargetMirrors()
+	if err != nil {
+		panic(err)
+	}
+	// create delegated targets manifests
+	delegatedTargets, err := m.GetDelegatedTargetMirrors()
+	if err != nil {
+		panic(err)
+	}
+
+	mirrorOutput := &TufMirrorOutput{
+		metadata:          metadataManifest,
+		delegatedMetadata: delegatedMetadata,
+		targets:           targets,
+		delegatedTargets:  delegatedTargets,
+	}
+
+	// push metadata and targets to registry (optional)
+	err = mirrorToRegistry(mirrorOutput)
+	if err != nil {
+		panic(err)
+	}
+
+	// save metadata and targets to local directory (optional)
+	mirrorOutputPath := filepath.Join(home, ".docker", "tuf", "mirror")
+	err = mirrorToLocal(mirrorOutput, mirrorOutputPath)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func mirrorToRegistry(o *TufMirrorOutput) error {
+	// push metadata to registry
+	metadataRepo := "registry-1.docker.io/docker/tuf-metadata:latest"
+	err := PushToRegistry(o.metadata, metadataRepo)
+	if err != nil {
+		return err
+	}
+	// push delegated metadata to registry
+	for _, metadata := range o.delegatedMetadata {
+		repo, _, ok := strings.Cut(metadataRepo, ":")
+		if !ok {
+			return fmt.Errorf("failed to get repo without tag: %s", metadataRepo)
+		}
+		imageName := fmt.Sprintf("%s:%s", repo, metadata.Tag)
+		err = PushToRegistry(metadata.Image, imageName)
+		if err != nil {
+			return err
+		}
+	}
+
+	// push top-level targets to registry
+	targetsRepo := "registry-1.docker.io/docker/tuf-targets"
+	for _, target := range o.targets {
+		imageName := fmt.Sprintf("%s:%s", targetsRepo, target.Tag)
+		err = PushToRegistry(target.Image, imageName)
+		if err != nil {
+			return err
+		}
+	}
+	// push delegated targets to registry
+	for _, target := range o.delegatedTargets {
+		imageName := fmt.Sprintf("%s:%s", targetsRepo, target.Tag)
+		err = PushToRegistry(target.Index, imageName)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func mirrorToLocal(o *TufMirrorOutput, outputPath string) error {
+	// output metadata to local directory
+	err := SaveAsOCILayout(o.metadata, outputPath)
+	if err != nil {
+		return err
+	}
+	// output delegated metadata to local directory
+	for _, metadata := range o.delegatedMetadata {
+		path := filepath.Join(outputPath, metadata.Tag)
+		err = SaveAsOCILayout(metadata.Image, path)
+		if err != nil {
+			return err
+		}
+	}
+
+	// output top-level targets to local directory
+	for _, target := range o.targets {
+		path := filepath.Join(outputPath, target.Tag)
+		err = SaveAsOCILayout(target.Image, path)
+		if err != nil {
+			return err
+		}
+	}
+	// output delegated targets to local directory
+	for _, target := range o.delegatedTargets {
+		path := filepath.Join(outputPath, target.Tag)
+		err = SaveAsOCILayout(target.Index, path)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}