package nbss

import (
	"bytes"
	"encoding/binary"

	osm "git.loafle.net/overflow/service_matcher-go"
)

const (
	NBSS_SESSION_REQUEST           uint8 = 0x81
	NBSS_POSITIVE_SESSION_RESPONSE uint8 = 0x82
	NBSS_NEGATIVE_SESSION_RESPONSE uint8 = 0x83
)

type NBSS struct {
	MsgType        uint8
	Flags          uint8 //0-6 : Reserved, must be zero. 7 : Length extension.
	Length         uint16
	CalledNameLen  uint8
	CalledName     [16]uint16
	_              uint8
	CallingNameLen uint8
	CallingName    [16]uint16
	_              uint8
}

type NBSSMatcher struct {
	osm.Matchers
}

func (t *NBSSMatcher) Key() string {
	return "NBSS"
}

func (t *NBSSMatcher) Name() string {
	return "NBSS"
}

func (t *NBSSMatcher) Meta() osm.Metadata {
	return nil
}

func (t *NBSSMatcher) IsPrePacket() bool {
	return false
}

func (t *NBSSMatcher) HasResponse(index int) bool {
	return true
}

func (t *NBSSMatcher) IsError(info osm.MatchInfo, index int, packet *osm.Packet) bool {
	return false
}

func (t *NBSSMatcher) Match(info osm.MatchInfo, index int, packet *osm.Packet) error {

	if packet == nil || !packet.Valid() {
		return osm.NoPacketReceivedError()
	}

	reader := new(bytes.Buffer)
	reader.Write(packet.Buffer)

	n := NBSS{}
	if err := binary.Read(reader, binary.LittleEndian, &n); err != nil {
		return osm.NotMatchedError()
	}

	switch n.MsgType {
	case NBSS_POSITIVE_SESSION_RESPONSE, NBSS_NEGATIVE_SESSION_RESPONSE:
	default:
		return osm.NotMatchedError()
	}

	return nil
}

func NewMatcher() osm.Matcher {

	m := &NBSSMatcher{}

	tempBuf := new(bytes.Buffer)
	binary.Write(tempBuf, binary.BigEndian, NBSS{})

	query := NBSS{
		MsgType:        NBSS_SESSION_REQUEST,
		Flags:          0x00,
		Length:         0x4400,
		CalledNameLen:  0x20,
		CallingNameLen: 0x20,
	}

	query.CalledName[0] = 0x4D45 // L
	query.CalledName[1] = 0x4745 // F

	query.CallingName[0] = 0x4D45
	query.CallingName[1] = 0x4745

	for i := 2; i < 16; i++ {
		query.CalledName[i] = 0x4143 //Space
		query.CallingName[i] = 0x4143
	}
	writer := new(bytes.Buffer)
	binary.Write(writer, binary.LittleEndian, query)

	m.AddPacket(osm.NewPacket(writer.Bytes(), writer.Len()))

	return m
}