maeqtt/mqtt/packets/Publish.go

package packets

import (
	"bufio"
	"bytes"
	"errors"
	"io"

	"badat.dev/maeqtt/v2/mqtt/properties"
	"badat.dev/maeqtt/v2/mqtt/types"
)

type PublishPacket struct {
	Dup        bool
	Retain     bool
	QOSLevel   byte
	TopicName  string
	Payload    []byte
	PacketId   *uint16
	Properties properties.PublishPacketProperties
}

func (p PublishPacket) Visit(v PacketVisitor) {
	v.VisitPublish(p)
}

func parsePublishPacket(control controlPacket) (PublishPacket, error) {
	var err error
	r := bufio.NewReader(control.reader)
	packet := PublishPacket{}

	if control.packetType != PacketTypePublish {
		return packet, errors.New("Wrong packet type for parseConnectPacket")
	}

	packet.Retain = control.flags&1 == 1
	packet.QOSLevel = byte((control.flags >> 1) & 0b11)
	packet.Dup = (control.flags>>3)&1 == 0

	packet.TopicName, err = types.DecodeUTF8String(r)
	if err != nil {
		return packet, err
	}

	if packet.QOSLevel != 0 {
		packId, err := types.DecodeUint16(r)
		if err != nil {
			return packet, err
		}
		packet.PacketId = &packId
	}
	err = properties.ParseProperties(r, packet.Properties.ArrayOf())
	if err != nil {
		return packet, err
	}

	packet.Payload, err = io.ReadAll(r)
	if err != nil {
		return packet, err
	}

	return packet, nil
}

func (p PublishPacket) Write(w io.Writer) error {
	buf := bytes.NewBuffer([]byte{})

	err := types.WriteUTF8String(buf, p.TopicName)
	if err != nil {
		return err
	}

	if p.PacketId != nil {
		err := types.WriteUint16(buf, *p.PacketId)
		if err != nil {
			return err
		}
	}

	err = properties.WriteProps(buf, p.Properties.ArrayOf())
	if err != nil {
		return err
	}

	buf.Write(p.Payload)

	flags := types.BoolToUint(p.Retain)
	flags += uint(p.QOSLevel) << 1
	flags += types.BoolToUint(p.Dup) << 3
	conPack := controlPacket{
		packetType: PacketTypePublish,
		flags:      flags,
		reader:     buf,
	}

	return conPack.write(w)
}