package main

import (
	"context"
	"fmt"
	"log"
	"regexp"
	"strings"

	"github.com/docker/docker/api/types/image"
	"github.com/docker/docker/client"
	"github.com/regclient/regclient"
	"github.com/regclient/regclient/types/ref"
)

// Wandelt ein ImageTag in registrykompatibles Format (ggf. registry hinzufügen)
func toRegistryImage(imageTag string) (string, error) {
	r := regexp.MustCompile(`^(?:(?P<registry>[^/]+)/)?(?P<repo>[^:]+)(?::(?P<tag>.+))?$`)
	match := r.FindStringSubmatch(imageTag)
	if len(match) == 0 {
		return "", fmt.Errorf("Image-Tag nicht erkannt: %s", imageTag)
	}
	registry := match[r.SubexpIndex("registry")]
	repo := match[r.SubexpIndex("repo")]
	tag := match[r.SubexpIndex("tag")]
	if registry == "" {
		registry = "registry-1.docker.io"
	}
	if tag == "" {
		tag = "latest"
	}
	return fmt.Sprintf("%s/%s:%s", registry, repo, tag), nil
}

// Extrahiert nur den reinen sha256:<...>-Digest
func extractDigest(s string) string {
	for _, part := range strings.Split(s, "@") {
		if strings.HasPrefix(part, "sha256:") {
			return part
		}
	}
	return s // ggf. nur die ID, wenn kein Digest
}

func main() {
	ctx := context.Background()
	cli, err := client.NewClientWithOpts(client.FromEnv)
	if err != nil {
		log.Fatal(err)
	}
	defer cli.Close()
	rc := regclient.New()

	images, err := cli.ImageList(ctx, image.ListOptions{All: true})
	if err != nil {
		log.Fatal(err)
	}

	for _, img := range images {
		for _, tag := range img.RepoTags {
			imageRef, err := toRegistryImage(tag)
			if err != nil {
				continue
			}

			// Lokalen Digest extrahieren
			var localDigest string
			if len(img.RepoDigests) > 0 {
				localDigest = extractDigest(img.RepoDigests[0])
			} else {
				localDigest = img.ID
			}

			// Remote-Digest bestimmen
			refObj, err := ref.New(imageRef)
			if err != nil {
				fmt.Printf("ImageRef-Fehler bei %s: %v\n", tag, err)
				continue
			}
			desc, err := rc.ManifestHead(ctx, refObj)
			if err != nil {
				fmt.Printf("Manifest nicht gefunden (%s): %v\n", tag, err)
				continue
			}
			remoteDigest := desc.GetDigest().String()

			fmt.Printf("Image: %s\n  Local Digest:  %s\n  Remote Digest: %s\n", tag, localDigest, remoteDigest)
			if localDigest == remoteDigest {
				fmt.Println("  -> Kein Update verfügbar.")
			} else {
				fmt.Println("  -> Update verfügbar!")
			}
		}
	}
}