package pubkey

import (
	"crypto/ed25519"
	"fmt"

	"git.sigsum.org/sigsum-go/pkg/hex"
	"git.sigsum.org/sigsum-tools-go/internal/util"
)

func Main(_ []string) error {
	b, err := util.HexFromStdin()
	if err != nil {
		return err
	}
	if len(b) != ed25519.PrivateKeySize {
		return fmt.Errorf("pubkey: invalid key size %d", len(b))
	}

	priv := ed25519.PrivateKey(b)
	pub, ok := priv.Public().(ed25519.PublicKey)
	if !ok {
		return fmt.Errorf("pubkey: must parse as ed25519")
	}

	fmt.Printf("%s\n", hex.Serialize(pub[:]))
	return nil
}