package ec256

import (
	"crypto/elliptic"
	"fmt"
	"math/big"

	"xdx.jelly/xgcl/internal"
)

const debug = false

func printFuncName() {
	if debug {
		fmt.Println("Calling " + internal.GetFuncName())
	}
}

var _ elliptic.Curve = SM2CurveParam{}

// SM2CurveParam CurveParams已经实现了crypto.Curve接口,增加一层把点乘等函数覆盖了。
type SM2CurveParam struct {
	*elliptic.CurveParams
}

type combinedMulter interface {
	CombinedMult(bigX, bigY *big.Int, baseScalar, scalar []byte) (x, y *big.Int)
}

// p = 2^256 - 2^224 - 2^96 + 2^64 -1
var c256 = SM2CurveParam{CurveParams: &elliptic.CurveParams{
	Name:    "Curve SM2",
	P:       bigFromBase16("FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFF"),
	N:       bigFromBase16("FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFF7203DF6B21C6052B53BBF40939D54123"),
	B:       bigFromBase16("28E9FA9E9D9F5E344D5A9E4BCF6509A7F39789F515AB8F92DDBCBD414D940E93"),
	Gx:      bigFromBase16("32C4AE2C1F1981195F9904466A39C9948FE30BBFF2660BE1715A4589334C74C7"),
	Gy:      bigFromBase16("BC3736A2F4F6779C59BDCEE36B692153D0A9877CC62A474002DF32E52139F0A0"),
	BitSize: 256},
}

var Curve256 = c256

// EC256 returns the sm2-curve
func EC256() elliptic.Curve {
	return c256
}

func CurveSM2() elliptic.Curve {
	return c256
}

func (SM2CurveParam) CombinedMult(bigX, bigY *big.Int, baseScalar, scalar []byte) (x, y *big.Int) {
	return CombinedMult(bigX, bigY, baseScalar, scalar)
}