package wrapper

/*
#cgo CFLAGS: -I../../ref/csidh
#cgo LDFLAGS: -L../../bin -lcsidh
#include <csidh.h>
*/
import "C"
import (
    "unsafe"

    csidh "github.com/henrydcase/nobs/dh/csidh"
)

const (
    PrvSz = 37
    PubSz = 64
    SsSz  = 64
)

type Ref struct {}

// Converts Golang's byte array to C's unsigned char. 'c' must
// have same size as byte
func (Ref) toBytes(c []C.uchar, b []byte) {
    if len(c) != len(b) {
        panic("len c!= len b")
    }
    for i,v := range(b) {
        c[i] = C.uchar(v)
    }
}

func (Ref) KeygenPrv() (prv csidh.PrivateKey) {
    var buf [PrvSz]C.uchar
    C.keygen_prv(&buf[0])
    prv.Import(C.GoBytes(unsafe.Pointer(&buf[0]), C.int(len(buf))))
    return
}

func (c Ref) KeygenPub(prv *csidh.PrivateKey) (pub csidh.PublicKey) {
    var prv_c_buf [PrvSz]C.uchar
    var pub_c_buf [PubSz]C.uchar
    var prv_g_buf [PrvSz]byte

    if !prv.Export(prv_g_buf[:]) {
        panic("Can't export private key")
    }
    c.toBytes(prv_c_buf[:], prv_g_buf[:])
    C.keygen_pub(&pub_c_buf[0], &prv_c_buf[0])
    pub.Import(C.GoBytes(unsafe.Pointer(&pub_c_buf[0]), C.int(len(pub_c_buf))))
    return
}

func (c Ref) Derive(ss []byte, pub *csidh.PublicKey, prv *csidh.PrivateKey) {
    var prv_c_buf [PrvSz]C.uchar
    var pub_c_buf [PubSz]C.uchar
    var prv_g_buf [PrvSz]byte
    var pub_g_buf [PubSz]byte
    var ss_c_buf [SsSz]C.uchar

    if !pub.Export(pub_g_buf[:]) {
        panic("Can't export public key")
    }

    if !prv.Export(prv_g_buf[:]) {
        panic("Can't export private key")
    }

    c.toBytes(pub_c_buf[:], pub_g_buf[:])
    c.toBytes(prv_c_buf[:], prv_g_buf[:])
    C.derive(&ss_c_buf[0], &pub_c_buf[0], &prv_c_buf[0])
    copy(ss, C.GoBytes(unsafe.Pointer(&ss_c_buf[0]), C.int(len(ss_c_buf))))
}

func (c Ref) Validate(a []byte) bool {
    var pub_c_buf [PubSz]C.uchar
    c.toBytes(pub_c_buf[:], a[:])
    return C.is_valid(&pub_c_buf[0]) != 0
}