// Copyright Fuzamei Corp. 2018 All Rights Reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Package btcutil Utility functions for Bitcoin elliptic curve cryptography.
package btcutil

import (
	"crypto/ecdsa"
	"math/big"
)

// ScalarBaseMult Multiplies the base G by a large integer.  The resulting
// point is represented as an ECDSA public key since that's
// typically how they're used.
func ScalarBaseMult(k *big.Int) *ecdsa.PublicKey {
	key := new(ecdsa.PublicKey)
	key.Curve = Secp256k1()
	key.X, key.Y = Secp256k1().ScalarBaseMult(k.Bytes())
	return key
}

// ScalarMult Multiply a large integer and a point.  The resulting point
// is represented as an ECDSA public key.
func ScalarMult(k *big.Int, B *ecdsa.PublicKey) *ecdsa.PublicKey {
	key := new(ecdsa.PublicKey)
	key.Curve = Secp256k1()
	key.X, key.Y = Secp256k1().ScalarMult(B.X, B.Y, k.Bytes())
	return key
}

// Add Adds two points to create a third.  Points are represented as
// ECDSA public keys.
func Add(a, b *ecdsa.PublicKey) *ecdsa.PublicKey {
	key := new(ecdsa.PublicKey)
	key.Curve = Secp256k1()
	key.X, key.Y = Secp256k1().Add(a.X, a.Y, b.X, b.Y)
	return key
}
