package utils

import (
	"crypto/elliptic"
	"crypto/x509/pkix"
	"encoding/asn1"
	"fmt"
	"reflect"
	"voucher/internal/pkg/cmb/sm2/model"
)

var (
	oidNamedCurveP256SM2 = asn1.ObjectIdentifier{1, 2, 156, 10197, 1, 301} // I get the SM2 ID through parsing the pem file generated by gmssl
)

// PKIXPublicKey reflects a PKIX public key structure. See SubjectPublicKeyInfo
// in RFC 3280.
type PKIXPublicKey struct {
	Algo      pkix.AlgorithmIdentifier
	BitString asn1.BitString
}

func ParsePublicKey(bytes []byte) (*model.PublicKey, error) {
	var pk PKIXPublicKey
	if _, err := asn1.Unmarshal(bytes, &pk); err != nil {
		return nil, err
	}
	if !reflect.DeepEqual(pk.Algo.Algorithm, oidSM2) {
		return nil, fmt.Errorf("not sm2 elliptic curve")
	}
	curve := NewP256Sm2()
	x, y := elliptic.Unmarshal(curve, pk.BitString.Bytes)
	return &model.PublicKey{
		Curve: curve,
		X:     x,
		Y:     y,
	}, nil
}