from io import BytesIO
from struct import unpack, calcsize
from typing import Dict, BinaryIO


class Unpacker:
    @staticmethod
    def from_bytes(data: bytes):
        return Unpacker({}, BytesIO(data))

    def __init__(self, formats: Dict[str, str], stream: BinaryIO, endianness: str = '>'):
        self.formats = formats
        self.stream = stream
        self.endianness = endianness

    def __getattribute__(self, item):
        try:
            return super(Unpacker, self).__getattribute__(item)
        except AttributeError:
            return self.unpack(item)

    def __getitem__(self, item):
        return self.unpack(item)

    def unpack(self, item):
        if item in self.formats:
            fmt = self.formats.get(item)
        else:
            fmt = item

        fmt = self.endianness + fmt

        size = calcsize(fmt)
        return unpack(fmt, self.stream.read(size))