package node

import (
	"sync"
	"vppn/fasttime"

	"golang.org/x/crypto/nacl/box"
)

// Encrypting the packet will also set the header's DataSize field.
func encryptPacketAsym(h *header, sharedKey, data, out []byte) []byte {
	out = out[:headerSize]
	h.Marshal(out)
	b := box.SealAfterPrecomputation(out[headerSize:headerSize], data, (*[24]byte)(out[:headerSize]), (*[32]byte)(sharedKey))
	return out[:len(b)+headerSize]
}

func decryptPacketAsym(sharedKey, packetAndHeader, out []byte) (decrypted []byte, ok bool) {
	return box.OpenAfterPrecomputation(
		out[:0],
		packetAndHeader[headerSize:],
		(*[24]byte)(packetAndHeader[:headerSize]),
		(*[32]byte)(sharedKey))
}

func computeSharedKey(peerPubKey, privKey []byte) []byte {
	shared := [32]byte{}
	box.Precompute(&shared, (*[32]byte)(peerPubKey), (*[32]byte)(privKey))
	return shared[:]
}

var (
	traceIDLock    sync.Mutex
	traceIDTime    uint64
	traceIDCounter uint64
)

func newTraceID() (id uint64) {
	traceIDLock.Lock()
	defer traceIDLock.Unlock()

	now := uint64(fasttime.Now())
	if traceIDTime < now {
		traceIDTime = now
		traceIDCounter = 0
	}
	traceIDCounter++

	return traceIDTime<<30 + traceIDCounter
}