ipv6

class Ipv6Address:
    def __init__(self, address: bytearray):
        assert len(address) == 16, address
        # I chose to store the address as the Big Int, because
        # it occupies less memory compared to bytearray in Python:
        # 232 (big int) vs 288 (bytearray)
        self.int_ = int.from_bytes(address, byteorder='big', signed=False)

    def __str__(self) -> str:
        parts = []
        addr = self.int_
        for _ in range(8):  # 8 groups of 2 bytes each
            v = addr & 0xFFFF
            part = '{:02X}'.format(v).removeprefix('0x').zfill(4)
            parts.append(part)
            addr >>= 16
        ret = ':'.join(reversed(parts))
        return ret

    def as_int(self) -> int:
        return self.int_

def addr_from_string(address: str) -> Ipv6Address:
    # example: 2345:0425:2CA1:0000:0000:0567:5673:23b5
    parts = address.split(':')
    ls = []
    for i in range(8):
        if i < len(parts) and parts[i] != '':
            part = bytearray.fromhex(parts[i])
        else:
            part = bytearray.fromhex('0x0000')
        ls.append(part)
    assert len(ls) == 8, ls
    return Ipv6Address(b''.join(ls))

class Ipv6Network:
    def __init__(self, addr:Ipv6Address, network_mask_bits:int):
        self.addr = addr
        self.network_mask_bits = network_mask_bits

    def __str__(self):
        return str(self.addr) + '/' + str(self.network_mask_bits)

    def contains(self, addr: Ipv6Address) -> bool:
        '''Returns True if the given address is within this network.'''
        low_bits = 128 - self.network_mask_bits
        net_addr_bits = self.addr.as_int() >> low_bits
        input_addr_bits = addr.as_int() >> low_bits
        return net_addr_bits == input_addr_bits

def main():
    addr1 : Ipv6Address = addr_from_string('0A0B:0001:0000:0000:0000:0000:0000:FF00')
    addr2 : Ipv6Address = addr_from_string('0A0B:FF00:0000:0000:0000:0000:FFFF:0000')
    addr3 : Ipv6Address = addr_from_string('0A0B:00FF:0000:0000:0000:0000:FFFF:0000')
    addr4 : Ipv6Address = addr_from_string('0A0A:0001:0000:0000:0000:0000:FFFF:0000')
    for addr in [addr1, addr2, addr3, addr4]:
        net = Ipv6Network(addr1, network_mask_bits=17)
        contains = net.contains(addr)
        if contains:
            print(f'Network [{net}] contains the address [{addr}]')
        else:
            print(f'Network [{net}] does not contain [{addr}]')

if __name__ == '__main__':
    main()