import MqttPacket from './MqttPacket'

export default class PacketReader {
  packet: MqttPacket
  pos: number = 0
  constructor (packet: MqttPacket) {
    this.packet = packet
  }

  readU8 (): number {
    const res = this.packet.content.readUInt8(this.pos)
    this.pos += 1
    return res
  }

  readU16 (): number {
    const res = this.packet.content.readUInt16BE(this.pos)
    this.pos += 2
    return res
  }

  readData (): Buffer {
    const size = this.readU16()
    const res = this.packet.content.slice(this.pos, size + 2)
    this.pos += size
    return res
  }

  readRaw (): Buffer {
    const res = this.packet.content.slice(
            this.pos,
            this.packet.content.length
        )
    this.pos = this.packet.content.length
    return res
  }
}