package mirror

import (
	"fmt"
	"path/filepath"
	"strings"

	"github.com/docker/attest/oci"
	v1 "github.com/google/go-containerregistry/pkg/v1"
	"github.com/google/go-containerregistry/pkg/v1/empty"
	"github.com/google/go-containerregistry/pkg/v1/mutate"
	"github.com/google/go-containerregistry/pkg/v1/static"
	"github.com/google/go-containerregistry/pkg/v1/types"
	"github.com/theupdateframework/go-tuf/v2/metadata"
)

// GetTUFTargetMirrors returns a list of top-level target files as MirrorImages (image with tag).
func (m *TUFMirror) GetTUFTargetMirrors() ([]*Image, error) {
	targetMirrors := []*Image{}
	md := m.TUFClient.GetMetadata()

	// for each top-level target file, create an image with the target file as a layer
	targets := md.Targets[metadata.TARGETS].Signed.Targets
	for _, t := range targets {
		// download target file
		file, err := m.TUFClient.DownloadTarget(t.Path, filepath.Join(m.tufPath, "download"))
		if err != nil {
			return nil, fmt.Errorf("failed to download target %s: %w", t.Path, err)
		}
		// create image with target file as layer
		img := empty.Image
		img = mutate.MediaType(img, types.OCIManifestSchema1)
		img = mutate.ConfigMediaType(img, types.OCIConfigJSON)
		// annotate layer
		hash, ok := t.Hashes["sha256"]
		if !ok {
			return nil, fmt.Errorf("missing sha256 hash for target %s", t.Path)
		}
		name := hash.String() + "." + t.Path
		ann := map[string]string{tufFileAnnotation: name}
		layer := mutate.Addendum{Layer: static.NewLayer(file.Data, tufTargetMediaType), Annotations: ann}
		img, err = mutate.Append(img, layer)
		if err != nil {
			return nil, fmt.Errorf("failed to append role layer to image: %w", err)
		}
		targetMirrors = append(targetMirrors, &Image{Image: &oci.EmptyConfigImage{Image: img}, Tag: name})
	}
	return targetMirrors, nil
}

// GetDelegatedTargetMirrors returns a list of delegated target files as MirrorIndexes (image index with tag)
// each image in the index contains a delegated target file.
func (m *TUFMirror) GetDelegatedTargetMirrors() ([]*Index, error) {
	mirror := []*Index{}
	md := m.TUFClient.GetMetadata()

	// for each delegated role, create an image index with target files as images
	roles := md.Targets[metadata.TARGETS].Signed.Delegations.Roles
	for _, role := range roles {
		// create an image index
		index := v1.ImageIndex(empty.Index)

		// get delegated targets metadata for role
		roleMeta, err := m.TUFClient.LoadDelegatedTargets(role.Name, metadata.TARGETS)
		if err != nil {
			return nil, fmt.Errorf("failed to load delegated targets metadata: %w", err)
		}

		// for each target file, create an image with the target file as a layer
		for _, target := range roleMeta.Signed.Targets {
			// download target file
			file, err := m.TUFClient.DownloadTarget(target.Path, filepath.Join(m.tufPath, "download"))
			if err != nil {
				return nil, fmt.Errorf("failed to download target %s: %w", target.Path, err)
			}
			// create image with target file as layer
			img := empty.Image
			img = mutate.MediaType(img, types.OCIManifestSchema1)
			img = mutate.ConfigMediaType(img, types.OCIConfigJSON)
			// annotate layer
			hash, ok := target.Hashes["sha256"]
			if !ok {
				return nil, fmt.Errorf("missing sha256 hash for target %s", target.Path)
			}
			filename := filepath.Base(target.Path)
			subdir, ok := strings.CutSuffix(target.Path, "/"+filename)
			if !ok {
				return nil, fmt.Errorf("failed to find target subdirectory [%s] in path: %s", subdir, target.Path)
			}
			name := hash.String() + "." + filename
			ann := map[string]string{tufFileAnnotation: name}
			layer := mutate.Addendum{Layer: static.NewLayer(file.Data, tufTargetMediaType), Annotations: ann}
			img, err = mutate.Append(img, layer)
			if err != nil {
				return nil, fmt.Errorf("failed to append role layer to image: %w", err)
			}
			emptyConfigImage := &oci.EmptyConfigImage{Image: img}
			// append image to index with annotation
			index = mutate.AppendManifests(index, mutate.IndexAddendum{
				Add: emptyConfigImage,
				Descriptor: v1.Descriptor{
					Annotations: map[string]string{
						tufFileAnnotation: fmt.Sprintf("%s/%s", subdir, name),
					},
				},
			})
		}
		mirror = append(mirror, &Index{Index: index, Tag: role.Name})
	}
	return mirror, nil
}