package meshtastic

import (
	"encoding/binary"
	"errors"
)

const (
	minPacketSize  = 4 + 4 + 4 + 1 + 1 + 1 + 1
	maxPayloadSize = 237
)

var (
	// ErrInvalidPacket signals the source buffer does not contain a valid packet.
	ErrInvalidPacket = errors.New("meshtastic: invalid packet")
)

type Packet struct {
	Destination   NodeID
	Source        NodeID
	ID            uint32
	Flags         uint8
	ChannelHash   uint8
	NextHop       uint8
	RelayNode     uint8
	PayloadLength int
	Payload       [maxPayloadSize]byte
}

func (packet *Packet) Decode(data []byte) error {
	if len(data) < minPacketSize {
		return ErrInvalidPacket
	}

	packet.Destination = parseNodeID(data[0:])
	packet.Source = parseNodeID(data[4:])
	packet.ID = binary.LittleEndian.Uint32(data[8:])
	packet.Flags = data[12]
	packet.ChannelHash = data[13]
	packet.NextHop = data[14]
	packet.RelayNode = data[15]
	packet.PayloadLength = len(data[16:])
	copy(packet.Payload[:], data[16:])

	return nil
}

func (packet *Packet) HopLimit() int {
	return
}

func parseNodeID(data []byte) NodeID {
	return NodeID(binary.LittleEndian.Uint32(data))
}