class NiimbotPacket:
    def __init__(self, type_, data):
        self.type = type_
        self.data = data

    @classmethod
    def from_bytes(cls, pkt):
        assert pkt[:2] == b'\x55\x55'
        assert pkt[-2:] == b'\xaa\xaa'
        type_ = pkt[2]
        len_ = pkt[3]
        data = pkt[4:4+len_]

        checksum = type_ ^ len_
        for i in data:
            checksum ^= i
        assert checksum == pkt[-3]

        return cls(type_, data)

    def to_bytes(self):
        checksum = self.type ^ len(self.data)
        for i in self.data:
            checksum ^= i
        return bytes((0x55, 0x55, self.type, len(self.data), *self.data, checksum, 0xaa, 0xaa))

    def __repr__(self):
        return f"<NiimbotPacket type={self.type} data={self.data}>"