package main

import (
	"encoding/base64"
	"log"
	"time"

	_ "github.com/containers/image/docker"

	"github.com/containers/image/transports"
	"github.com/containers/image/types"
)

func main() {
	t := transports.Get("docker")
	ref, err := t.ParseReference("//registry.access.redhat.com/rhel7@sha256:582cb940a6e730dbdffee7cc5e1983522fdeeb3c40bea7373b255a209124cc02")
	if err != nil {
		log.Fatalf(err.Error())
	}
	context := types.SystemContext{}
	source, err := ref.NewImageSource(&context, nil)
	if err != nil {
		log.Fatalf(err.Error())
	}
	defer source.Close()
	errChan := make(chan error)
	var signatures [][]byte
	go func() {
		var getSignatureErr error
		signatures, getSignatureErr = source.GetSignatures()
		errChan <- getSignatureErr
	}()
	select {
	case err := <-errChan:
		if err != nil {
			log.Fatalf("error getting signatures: %v", err)
		}
	case <-time.After(time.Second * 20):
		log.Fatalf("timeout getting signatures")
	}
	for n, s := range signatures {
		log.Printf("signature #%d: %s", n, base64.StdEncoding.EncodeToString(s))
	}
	log.Printf("done")
}