const (
	PingPacket = iota + 1 // zero is 'reserved'
	PongPacket
	FindnodePacket
	NeighborsPacket
	ENRRequestPacket
	ENRResponsePacket
)

const MaxNeighbors = 12

var (
	ErrPacketTooSmall = errors.New("too small")
	ErrBadHash        = errors.New("bad hash")
	ErrBadPoint       = errors.New("invalid curve point")
)

type ENRRequest struct {
	Expiration uint64
	// Ignore additional fields (for forward compatibility).
	Rest []rlp.RawValue `rlp:"tail"`
}

type ENRResponse struct {
	ReplyTok []byte // Hash of the ENRRequest packet.
	Record   enr.Record
	// Ignore additional fields (for forward compatibility).
	Rest []rlp.RawValue `rlp:"tail"`
}

type Endpoint struct {
	IP  net.IP // len 4 for IPv4 or 16 for IPv6
	UDP uint16 // for discovery protocol
	TCP uint16 // for RLPx protocol
}

type Findnode struct {
	Target     Pubkey
	Expiration uint64
	// Ignore additional fields (for forward compatibility).
	Rest []rlp.RawValue `rlp:"tail"`
}

type Neighbors struct {
	Nodes      []Node
	Expiration uint64
	// Ignore additional fields (for forward compatibility).
	Rest []rlp.RawValue `rlp:"tail"`
}

type Node struct {
	IP  net.IP // len 4 for IPv4 or 16 for IPv6
	UDP uint16 // for discovery protocol
	TCP uint16 // for RLPx protocol
	ID  Pubkey
}

type Packet interface {
	// Name is the name of the package, for logging purposes.
	Name() string
	// Kind is the packet type, for logging purposes.
	Kind() byte
}

type Ping struct {
	Version    uint
	From, To   Endpoint
	Expiration uint64
	ENRSeq     uint64 `rlp:"optional"` // Sequence number of local record, added by EIP-868.

	// Ignore additional fields (for forward compatibility).
	Rest []rlp.RawValue `rlp:"tail"`
}

type Pong struct {
	// This field should mirror the UDP envelope address
	// of the ping packet, which provides a way to discover the
	// external address (after NAT).
	To         Endpoint
	ReplyTok   []byte // This contains the hash of the ping packet.
	Expiration uint64 // Absolute timestamp at which the packet becomes invalid.
	ENRSeq     uint64 `rlp:"optional"` // Sequence number of local record, added by EIP-868.

	// Ignore additional fields (for forward compatibility).
	Rest []rlp.RawValue `rlp:"tail"`
}

type Pubkey [64]byte