Yepoleb.python-a2s/a2s/a2s_async.py

from __future__ import annotations

import asyncio
import io
import logging
import time
from typing import TYPE_CHECKING, Dict, List, NoReturn, Optional, Tuple, Type, TypeVar, Union, overload

from a2s.a2s_fragment import A2SFragment, decode_fragment
from a2s.byteio import ByteReader
from a2s.defaults import DEFAULT_RETRIES
from a2s.exceptions import BrokenMessageError

from .info import GoldSrcInfo, InfoProtocol, SourceInfo
from .players import Player, PlayersProtocol
from .rules import RulesProtocol

if TYPE_CHECKING:
    from typing_extensions import Self

HEADER_SIMPLE = b"\xFF\xFF\xFF\xFF"
HEADER_MULTI = b"\xFE\xFF\xFF\xFF"
A2S_CHALLENGE_RESPONSE = 0x41
PROTOCOLS = Union[InfoProtocol, PlayersProtocol, RulesProtocol]

logger: logging.Logger = logging.getLogger("a2s")

T = TypeVar("T", InfoProtocol, PlayersProtocol, RulesProtocol)


@overload
async def request_async(
    address: Tuple[str, int], timeout: float, encoding: str, a2s_proto: Type[InfoProtocol]
) -> Union[SourceInfo, GoldSrcInfo]:
    ...


@overload
async def request_async(
    address: Tuple[str, int], timeout: float, encoding: str, a2s_proto: Type[PlayersProtocol]
) -> List[Player]:
    ...


@overload
async def request_async(
    address: Tuple[str, int], timeout: float, encoding: str, a2s_proto: Type[RulesProtocol]
) -> Dict[Union[str, bytes], Union[str, bytes]]:
    ...


async def request_async(
    address: Tuple[str, int], timeout: float, encoding: str, a2s_proto: Type[T]
) -> Union[SourceInfo, GoldSrcInfo, List[Player], Dict[Union[str, bytes], Union[str, bytes]]]:
    conn = await A2SStreamAsync.create(address, timeout)
    response = await request_async_impl(conn, encoding, a2s_proto)
    conn.close()
    return response


@overload
async def request_async_impl(
    conn: A2SStreamAsync,
    encoding: str,
    a2s_proto: Type[InfoProtocol],
    challenge: int = ...,
    retries: int = ...,
    ping: Optional[float] = ...,
) -> Union[SourceInfo, GoldSrcInfo]:
    ...


@overload
async def request_async_impl(
    conn: A2SStreamAsync,
    encoding: str,
    a2s_proto: Type[PlayersProtocol],
    challenge: int = ...,
    retries: int = ...,
    ping: Optional[float] = ...,
) -> List[Player]:
    ...


@overload
async def request_async_impl(
    conn: A2SStreamAsync,
    encoding: str,
    a2s_proto: Type[RulesProtocol],
    challenge: int = ...,
    retries: int = ...,
    ping: Optional[float] = ...,
) -> Dict[Union[str, bytes], Union[str, bytes]]:
    ...


async def request_async_impl(
    conn: A2SStreamAsync,
    encoding: str,
    a2s_proto: Type[T],
    challenge: int = 0,
    retries: int = 0,
    ping: Optional[float] = None,
) -> Union[SourceInfo, GoldSrcInfo, Dict[Union[str, bytes], Union[str, bytes]], List[Player]]:
    send_time = time.monotonic()
    resp_data = await conn.request(a2s_proto.serialize_request(challenge))
    recv_time = time.monotonic()
    # Only set ping on first packet received
    if retries == 0:
        ping = recv_time - send_time

    reader = ByteReader(io.BytesIO(resp_data), endian="<", encoding=encoding)

    response_type = reader.read_uint8()
    if response_type == A2S_CHALLENGE_RESPONSE:
        if retries >= DEFAULT_RETRIES:
            raise BrokenMessageError("Server keeps sending challenge responses")
        challenge = reader.read_uint32()
        return await request_async_impl(conn, encoding, a2s_proto, challenge, retries + 1, ping)

    if not a2s_proto.validate_response_type(response_type):
        raise BrokenMessageError("Invalid response type: " + hex(response_type))

    return a2s_proto.deserialize_response(reader, response_type, ping)


class A2SProtocol(asyncio.DatagramProtocol):
    __slots__ = (
        "recv_queue",
        "error_event",
        "error",
        "fragment_buf",
        "transport",
    )

    def __init__(self):
        self.recv_queue: asyncio.Queue[bytes] = asyncio.Queue()
        self.error_event: asyncio.Event = asyncio.Event()
        self.error: Optional[Exception] = None
        self.fragment_buf: List[A2SFragment] = []

    def connection_made(self, transport: asyncio.DatagramTransport) -> None:
        self.transport: asyncio.DatagramTransport = transport

    def datagram_received(self, data: bytes, addr: Tuple[str, int]) -> None:
        header = data[:4]
        payload = data[4:]
        if header == HEADER_SIMPLE:
            logger.debug("Received single packet: %r", payload)
            self.recv_queue.put_nowait(payload)
        elif header == HEADER_MULTI:
            self.fragment_buf.append(decode_fragment(payload))
            if len(self.fragment_buf) < self.fragment_buf[0].fragment_count:
                return  # Wait for more packets to arrive
            self.fragment_buf.sort(key=lambda f: f.fragment_id)
            reassembled = b"".join(fragment.payload for fragment in self.fragment_buf)
            # Sometimes there's an additional header present
            if reassembled.startswith(b"\xFF\xFF\xFF\xFF"):
                reassembled = reassembled[4:]
            logger.debug("Received %s part packet with content: %r", len(self.fragment_buf), reassembled)
            self.recv_queue.put_nowait(reassembled)
            self.fragment_buf = []
        else:
            self.error = BrokenMessageError("Invalid packet header: " + repr(header))
            self.error_event.set()

    def error_received(self, exc: Exception) -> None:
        self.error = exc
        self.error_event.set()

    def raise_on_error(self) -> NoReturn:
        assert self.error
        error: Exception = self.error
        self.error = None
        self.error_event.clear()
        raise error


class A2SStreamAsync:
    __slots__ = (
        "transport",
        "protocol",
        "timeout",
    )

    def __init__(self, transport: asyncio.DatagramTransport, protocol: A2SProtocol, timeout: float) -> None:
        self.transport: asyncio.DatagramTransport = transport
        self.protocol: A2SProtocol = protocol
        self.timeout: float = timeout

    def __del__(self) -> None:
        self.close()

    @classmethod
    async def create(cls, address: Tuple[str, int], timeout: float) -> Self:
        loop = asyncio.get_running_loop()
        transport, protocol = await loop.create_datagram_endpoint(lambda: A2SProtocol(), remote_addr=address)
        return cls(transport, protocol, timeout)

    def send(self, payload: bytes) -> None:
        logger.debug("Sending packet: %r", payload)
        packet = HEADER_SIMPLE + payload
        self.transport.sendto(packet)

    async def recv(self) -> bytes:
        queue_task = asyncio.create_task(self.protocol.recv_queue.get())
        error_task = asyncio.create_task(self.protocol.error_event.wait())
        done, pending = await asyncio.wait(
            {queue_task, error_task}, timeout=self.timeout, return_when=asyncio.FIRST_COMPLETED
        )

        for task in pending:
            task.cancel()
        if error_task in done:
            self.protocol.raise_on_error()
        if not done:
            raise asyncio.TimeoutError()

        return queue_task.result()

    async def request(self, payload: bytes) -> bytes:
        self.send(payload)
        return await self.recv()

    def close(self) -> None:
        self.transport.close()