package cosign

import (
	"bytes"
	"fmt"

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

func Main(_ []string, optPriv, optPub string) error {
	priv, err := util.SignerFromHex(optPriv)
	if err != nil {
		return fmt.Errorf("cosign: %v", err)
	}
	b, err := hex.Deserialize(optPub)
	if err != nil {
		return fmt.Errorf("cosign: %v", err)
	}
	if len(b) != types.PublicKeySize {
		return fmt.Errorf("cosign: invalid public key length %d", len(b))
	}
	var pub types.PublicKey
	copy(pub[:], b)
	data, err := util.BytesFromStdin()
	if err != nil {
		return fmt.Errorf("cosign: %v", err)
	}
	var sth types.SignedTreeHead
	if err := sth.FromASCII(bytes.NewBuffer(data)); err != nil {
		return fmt.Errorf("cosign: %v", err)
	}
	witSTH, err := sth.TreeHead.Sign(priv, types.HashFn(pub[:]))
	if err != nil {
		return fmt.Errorf("cosign: %v", err)
	}

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