conqp.rcon/rcon/source/proto.py

"""Low-level protocol stuff."""

from __future__ import annotations
from asyncio import StreamReader
from enum import Enum
from functools import partial
from logging import getLogger
from random import randint
from typing import IO, NamedTuple

from rcon.exceptions import EmptyResponse


__all__ = ['LittleEndianSignedInt32', 'Type', 'Packet', 'random_request_id']


LOGGER = getLogger(__file__)
TERMINATOR = b'\x00\x00'


class LittleEndianSignedInt32(int):
    """A little-endian, signed int32."""

    MIN = -2_147_483_648
    MAX = 2_147_483_647

    def __init__(self, *_):
        """Check the boundaries."""
        super().__init__()

        if not self.MIN <= self <= self.MAX:
            raise ValueError('Signed int32 out of bounds:', int(self))

    def __bytes__(self):
        """Return the integer as signed little endian."""
        return self.to_bytes(4, 'little', signed=True)

    @classmethod
    async def aread(cls, reader: StreamReader) -> LittleEndianSignedInt32:
        """Read the integer from an asynchronous file-like object."""
        return cls.from_bytes(await reader.read(4), 'little', signed=True)

    @classmethod
    def read(cls, file: IO) -> LittleEndianSignedInt32:
        """Read the integer from a file-like object."""
        return cls.from_bytes(file.read(4), 'little', signed=True)


class Type(Enum):
    """RCON packet types."""

    SERVERDATA_AUTH = LittleEndianSignedInt32(3)
    SERVERDATA_AUTH_RESPONSE = LittleEndianSignedInt32(2)
    SERVERDATA_EXECCOMMAND = LittleEndianSignedInt32(2)
    SERVERDATA_RESPONSE_VALUE = LittleEndianSignedInt32(0)

    def __int__(self):
        """Return the actual integer value."""
        return int(self.value)

    def __bytes__(self):
        """Return the integer value as little endian."""
        return bytes(self.value)

    @classmethod
    async def aread(cls, reader: StreamReader, *, prefix: str = '') -> Type:
        """Read the type from an asynchronous file-like object."""
        LOGGER.debug('%sReading type asynchronously.', prefix)
        value = await LittleEndianSignedInt32.aread(reader)
        LOGGER.debug('%s  => value: %i', prefix, value)
        return cls(value)

    @classmethod
    def read(cls, file: IO, *, prefix: str = '') -> Type:
        """Read the type from a file-like object."""
        LOGGER.debug('%sReading type.', prefix)
        value = LittleEndianSignedInt32.read(file)
        LOGGER.debug('%s  => value: %i', prefix, value)
        return cls(value)


class Packet(NamedTuple):
    """An RCON packet."""

    id: LittleEndianSignedInt32
    type: Type
    payload: bytes
    terminator: bytes = TERMINATOR

    def __add__(self, other: Packet | None) -> Packet:
        if other is None:
            return self

        if other.id != self.id:
            raise ValueError('Can only add packages with same id.')

        if other.type != self.type:
            raise ValueError('Can only add packages of same type.')

        if other.terminator != self.terminator:
            raise ValueError('Can only add packages with same terminator.')

        return Packet(
            self.id,
            self.type,
            self.payload + other.payload,
            self.terminator
        )

    def __radd__(self, other: Packet | None) -> Packet:
        if other is None:
            return self

        return other.__add__(self)

    def __bytes__(self):
        """Return the packet as bytes with prepended length."""
        payload = bytes(self.id)
        payload += bytes(self.type)
        payload += self.payload
        payload += self.terminator
        size = bytes(LittleEndianSignedInt32(len(payload)))
        return size + payload

    @classmethod
    async def aread(cls, reader: StreamReader) -> Packet:
        """Read a packet from an asynchronous file-like object."""
        LOGGER.debug('Reading packet asynchronously.')
        size = await LittleEndianSignedInt32.aread(reader)
        LOGGER.debug('  => size: %i', size)

        if not size:
            raise EmptyResponse()

        id_ = await LittleEndianSignedInt32.aread(reader)
        LOGGER.debug('  => id: %i', id_)
        type_ = await Type.aread(reader, prefix='  ')
        LOGGER.debug('  => type: %i', type_)
        payload = await reader.read(size - 10)
        LOGGER.debug('  => payload: %s', payload)
        terminator = await reader.read(2)
        LOGGER.debug('  => terminator: %s', terminator)

        if terminator != TERMINATOR:
            LOGGER.warning('Unexpected terminator: %s', terminator)

        return cls(id_, type_, payload, terminator)

    @classmethod
    def read(cls, file: IO) -> Packet:
        """Read a packet from a file-like object."""
        LOGGER.debug('Reading packet.')
        size = LittleEndianSignedInt32.read(file)
        LOGGER.debug('  => size: %i', size)

        if not size:
            raise EmptyResponse()

        id_ = LittleEndianSignedInt32.read(file)
        LOGGER.debug('  => id: %i', id_)
        type_ = Type.read(file, prefix='  ')
        LOGGER.debug('  => type: %i', type_)
        payload = file.read(size - 10)
        LOGGER.debug('  => payload: %s', payload)
        terminator = file.read(2)
        LOGGER.debug('  => terminator: %s', terminator)

        if terminator != TERMINATOR:
            LOGGER.warning('Unexpected terminator: %s', terminator)

        return cls(id_, type_, payload, terminator)

    @classmethod
    def make_command(cls, *args: str, encoding: str = 'utf-8') -> Packet:
        """Create a command packet."""
        return cls(
            random_request_id(), Type.SERVERDATA_EXECCOMMAND,
            b' '.join(map(partial(str.encode, encoding=encoding), args))
        )

    @classmethod
    def make_login(cls, passwd: str, *, encoding: str = 'utf-8') -> Packet:
        """Create a login packet."""
        return cls(
            random_request_id(), Type.SERVERDATA_AUTH, passwd.encode(encoding)
        )


def random_request_id() -> LittleEndianSignedInt32:
    """Generate a random request ID."""

    return LittleEndianSignedInt32(randint(0, LittleEndianSignedInt32.MAX))