import dataclasses
from typing import Literal

import bitstring

# Reference for H10301 card format:
# https://www.hidglobal.com/sites/default/files/hid-understanding_card_data_formats-wp-en.pdf


class InvalidHexCode(Exception):
    pass


class Not26Bit(InvalidHexCode):
    def __init__(self) -> None:
        super().__init__("Card number > 26 bits")


class InvalidParity(InvalidHexCode):
    def __init__(self, even_odd: Literal["even", "odd"]) -> None:
        super().__init__(f"Bad {even_odd} parity")


@dataclasses.dataclass(frozen=True)
class Credential:
    bits: bitstring.Bits

    @classmethod
    def from_code(cls, facility=int, card_number=int) -> "Credential":
        bits = bitstring.pack(
            "0b000000, 0b0, uint:8=facility, uint:16=card_number, 0b0",
            facility=facility,
            card_number=card_number,
        )
        bits[6] = bits[7:19].count(1) % 2  # even parity
        bits[31] = bits[19:31].count(0) % 2  # odd parity
        return cls(bits)

    @classmethod
    def from_hex(cls, hex_code: str) -> "Credential":
        bits = bitstring.Bits(hex=hex_code)

        if bits[:6].any(1):
            raise Not26Bit
        if bits[6] != bits[7:19].count(1) % 2:
            raise InvalidParity("even")
        if bits[31] != (bits[19:31].count(0) % 2):
            raise InvalidParity("odd")

        return cls(bits)

    @property
    def facility_code(self) -> int:
        return self.bits[7:15].uint

    @property
    def card_number(self) -> int:
        return self.bits[15:31].uint

    @property
    def hex(self) -> str:
        return self.bits.hex.upper()