package dcrypto

import (
	"crypto/ecdh"
	"crypto/rand"
)

var (
	// DefaultDHCurve is the default elliptic curve used for signing.
	DefaultDHCurve = ecdh.P384
)

// GenerateDHKey generates a new ECDH private key for key exchange.
func GenerateDHKey() (*ecdh.PrivateKey, error) {
	return DefaultDHCurve().GenerateKey(rand.Reader)
}

// ComputeDHSecret computes the shared secret from the private key and the public key.
func ComputeDHSecret(priv *ecdh.PrivateKey, pub *ecdh.PublicKey) ([]byte, error) {
	return priv.ECDH(pub)
}

// ExportDHPublicKey exports the public key as a byte slice.
func ExportDHPublicKey(pub *ecdh.PublicKey) ([]byte, error) {
	return pub.Bytes(), nil
}

// ImportDHPublicKey imports the public key from a byte slice.
func ImportDHPublicKey(data []byte) (*ecdh.PublicKey, error) {
	return DefaultDHCurve().NewPublicKey(data)
}