# Copyright (C) 2020 by eichhornchen, ÿnérant
# SPDX-License-Identifier: GPL-3.0-or-later

import socket
from argparse import ArgumentParser
from enum import Enum
from ipaddress import IPv6Address
from typing import Any, Optional, Tuple


class Squinnondation:
    args: Any
    bind_address: str
    bind_port: int
    client_address: str
    client_port: int

    def parse_arguments(self) -> None:
        parser = ArgumentParser(description="MIRC client.")
        parser.add_argument('bind_address', type=str, default="localhost",
                            help="Address of the client.")
        parser.add_argument('bind_port', type=int, default=2500,
                            help="Port of the client. Must be between 1024 and 65535.")
        parser.add_argument('--client_address', type=str, default="localhost",
                            help="Address of the first neighbour.")
        parser.add_argument('--client_port', type=int, default=2500,
                            help="Port of the first neighbour. Must be between 1024 and 65535.")
        parser.add_argument('--bind-only', '-b', action='store_true',
                            help="Don't connect to another client, only listen to connections.")
        self.args = parser.parse_args()

        if not (1024 <= self.args.bind_port <= 65535) and (1024 <= self.args.client_port <= 65535):
            raise ValueError("Ports must be between 1024 and 65535.")

        self.bind_address = self.args.bind_address
        self.bind_port = self.args.bind_port
        self.client_address = self.args.client_address
        self.client_port = self.args.client_port

    @staticmethod
    def main() -> None:  # pragma: no cover
        instance = Squinnondation()
        instance.parse_arguments()

        squirrel = Squirrel(input("Enter your nickname: "), instance.bind_address, instance.bind_port)

        if not instance.args.bind_only:
            hazelnut = Hazelnut(address=instance.client_address, port=instance.client_port)
            pkt = Packet()
            pkt.magic = 95
            pkt.version = 0
            pkt.body = DataTLV()
            msg = f"Hello world, my name is {squirrel.nickname}!"
            pkt.body.data = msg.encode("UTF-8")
            pkt.body.sender_id = 42
            pkt.body.nonce = 18
            pkt.body.length = len(msg) + 1 + 1 + 8 + 4
            pkt.body_length = pkt.body.length + 2
            squirrel.send_packet(hazelnut, pkt)

        while True:
            pkt, addr = squirrel.receive_packet()
            print(f"received message: {pkt.body.data.decode('UTF-8')}")


class TLV:
    """
    The Tag-Length-Value contains the different type of data that can be sent.
    TODO: add subclasses for each type of TLV
    """
    type: int

    def unmarshal(self, raw_data: bytes) -> None:
        """
        Parse data and construct TLV.
        """
        raise NotImplementedError

    def marshal(self) -> bytes:
        """
        Translate the TLV into a byte array.
        """
        raise NotImplementedError

    def validate_data(self) -> bool:
        """
        Ensure that the TLV is well-formed.
        Raises a ValueError if it is not the case.
        TODO: Make some tests
        """
        return True

    @staticmethod
    def tlv_classes():
        return [Pad1TLV, PadNTLV, HelloTLV, NeighbourTLV, DataTLV, AckTLV, GoAwayTLV, WarningTLV]


class Pad1TLV(TLV):
    """
    This TLV is simply ignored.
    """
    type: int = 0

    def unmarshal(self, raw_data: bytes) -> None:
        """
        There is nothing to do. We ignore the packet.
        """
        self.type = raw_data[0]

    def marshal(self) -> bytes:
        """
        The TLV is empty.
        """
        return self.type.to_bytes(1, "big")


class PadNTLV(TLV):
    """
    This TLV is filled with zeros. It is ignored.
    """
    type: int = 1
    length: int
    mbz: bytes

    def validate_data(self) -> bool:
        if self.mbz != int(0).to_bytes(self.length, "big"):
            raise ValueError("The body of a PadN TLV is not filled with zeros.")
        return True

    def unmarshal(self, raw_data: bytes) -> None:
        """
        Store the zero-array, then ignore the packet.
        """
        self.type = raw_data[0]
        self.length = raw_data[1]
        self.mbz = raw_data[2:2 + self.length]

    def marshal(self) -> bytes:
        """
        Construct the byte array filled by zeros.
        """
        return self.type.to_bytes(1, "big") + self.length.to_bytes(1, "big") + self.mbz[:self.length]


class HelloTLV(TLV):
    type: int = 2
    length: int
    source_id: int
    dest_id: Optional[int]

    def validate_data(self) -> bool:
        if self.length != 8 and self.length != 16:
            raise ValueError("The length of a Hello TLV must be 8 for a short Hello, or 16 for a long Hello,"
                             f"found {self.length}")
        return True

    def unmarshal(self, raw_data: bytes) -> None:
        self.type = raw_data[0]
        self.length = raw_data[1]
        self.source_id = int.from_bytes(raw_data[2:10], "big")
        if self.length == 16:
            self.dest_id = int.from_bytes(raw_data[10:18], "big")

    def marshal(self) -> bytes:
        data = self.type.to_bytes(1, "big") + self.length.to_bytes(1, "big") + self.source_id.to_bytes(8, "big")
        if self.dest_id:
            data += self.dest_id.to_bytes(8, "big")
        return data


class NeighbourTLV(TLV):
    type: int = 3
    length: int
    ip_address: IPv6Address
    port: int

    def unmarshal(self, raw_data: bytes) -> None:
        self.type = raw_data[0]
        self.length = raw_data[1]
        self.ip_address = IPv6Address(raw_data[2:18])
        self.port = int.from_bytes(raw_data[18:20], "big")

    def marshal(self) -> bytes:
        return self.type.to_bytes(1, "big") + \
               self.length.to_bytes(1, "big") + \
               self.ip_address.packed + \
               self.port.to_bytes(2, "big")


class DataTLV(TLV):
    type: int = 4
    length: int
    sender_id: int
    nonce: int
    data: bytes

    def unmarshal(self, raw_data: bytes) -> None:
        self.type = raw_data[0]
        self.length = raw_data[1]
        self.sender_id = int.from_bytes(raw_data[2:10], "big")
        self.nonce = int.from_bytes(raw_data[10:14], "big")
        self.data = raw_data[14:2 + self.length]

    def marshal(self) -> bytes:
        return self.type.to_bytes(1, "big") + \
               self.length.to_bytes(1, "big") + \
               self.sender_id.to_bytes(8, "big") + \
               self.nonce.to_bytes(4, "big") + \
               self.data


class AckTLV(TLV):
    type: int = 5
    length: int
    sender_id: int
    nonce: int

    def unmarshal(self, raw_data: bytes) -> None:
        self.type = raw_data[0]
        self.length = raw_data[1]
        self.sender_id = int.from_bytes(raw_data[2:10], "big")
        self.nonce = int.from_bytes(raw_data[10:14], "big")

    def marshal(self) -> bytes:
        return self.type.to_bytes(1, "big") + \
               self.length.to_bytes(1, "big") + \
               self.sender_id.to_bytes(8, "big") + \
               self.nonce.to_bytes(4, "big")


class GoAwayTLV(TLV):
    class GoAwayType(Enum):
        UNKNOWN = 0
        EXIT = 1
        TIMEOUT = 2
        PROTOCOL_VIOLATION = 3

    type: int = 6
    length: int
    code: GoAwayType
    message: str

    def unmarshal(self, raw_data: bytes) -> None:
        self.type = raw_data[0]
        self.length = raw_data[1]
        self.code = GoAwayTLV.GoAwayType(raw_data[2])
        self.message = raw_data[3:self.length - 1].decode("UTF-8")

    def marshal(self) -> bytes:
        return self.type.to_bytes(1, "big") + \
               self.length.to_bytes(1, "big") + \
               self.code.value.to_bytes(1, "big") + \
               self.message.encode("UTF-8")[:self.length - 1]


class WarningTLV(TLV):
    type: int = 7
    length: int
    message: str

    def unmarshal(self, raw_data: bytes) -> None:
        self.type = raw_data[0]
        self.length = raw_data[1]
        self.message = raw_data[2:self.length].decode("UTF-8")

    def marshal(self) -> bytes:
        return self.type.to_bytes(1, "big") + \
               self.length.to_bytes(1, "big") + \
               self.message.encode("UTF-8")[:self.length]


class Packet:
    """
    A Packet is a wrapper around the
    """
    magic: int
    version: int
    body_length: int
    body: TLV

    def validate_data(self) -> bool:
        """
        Ensure that the packet is well-formed.
        Raises a ValueError if the packet contains bad data.
        """
        if self.magic != 95:
            raise ValueError("The magic code of the packet must be 95, found: {:d}".format(self.magic))
        if self.version != 0:
            raise ValueError("The version of the packet is not supported: {:d}".format(self.version))
        if not (0 <= self.body_length <= 120):
            raise ValueError("The body length of the packet is negative or too high. It must be between 0 and 1020,"
                             "found: {:d}".format(self.body_length))
        return self.body.validate_data()

    @staticmethod
    def unmarshal(data: bytes) -> "Packet":
        """
        Read raw data and build the packet wrapper.
        Raises a ValueError whenever the data is invalid.
        """
        pkt = Packet()
        pkt.magic = data[0]
        pkt.version = data[1]
        pkt.body_length = int.from_bytes(data[2:4], byteorder="big")
        tlv_type = data[4]
        if not (0 <= tlv_type < len(TLV.tlv_classes())):
            raise ValueError(f"TLV type is not supported: {tlv_type}")
        pkt.body = TLV.tlv_classes()[tlv_type]()
        pkt.body.unmarshal(data[4:4+pkt.body_length])

        pkt.validate_data()

        return pkt

    def marshal(self) -> bytes:
        """
        Compute the byte array data associated to the packet.
        """
        data = self.magic.to_bytes(1, "big")
        data += self.version.to_bytes(1, "big")
        data += self.body_length.to_bytes(2, "big")
        data += self.body.marshal()
        return data


class Hazelnut:
    """
    A hazelnut is a connected client, with its socket.
    """
    def __init__(self, nickname: str = "anonymous", address: str = "localhost", port: int = 2500):
        self.nickname = nickname
        # Resolve DNS as an IPv6
        address = socket.getaddrinfo(address, None, socket.AF_INET6)[0][4][0]
        self.address = IPv6Address(address)
        self.port = port


class Squirrel(Hazelnut):
    """
    The squirrel is the user of the program. It can speak with other clients, that are called hazelnuts.
    """
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.socket = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
        self.socket.bind((str(self.address), self.port))
        print(f"Listening on {self.address}:{self.port}")

    def send_packet(self, client: Hazelnut, pkt: Packet) -> int:
        """
        Send a formatted packet to a client.
        """
        return self.send_raw_data(client, pkt.marshal())

    def send_raw_data(self, client: Hazelnut, data: bytes) -> int:
        """
        Send a raw packet to a client.
        """
        return self.socket.sendto(data, (str(client.address), client.port))

    def receive_packet(self) -> Tuple[Packet, Any]:
        """
        Receive a packet from the socket and translate it into a Python object.
        TODO: Translate the address into the correct hazelnut.
        """
        data, addr = self.receive_raw_data()
        return Packet.unmarshal(data), addr

    def receive_raw_data(self) -> Tuple[bytes, Any]:
        """
        Receive a packet from the socket.
        TODO: Translate the address into the correct hazelnut.
        """
        return self.socket.recvfrom(1024)