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|
"""Low-level protocol stuff."""
from __future__ import annotations
from typing import NamedTuple
from zlib import crc32
__all__ = [
"HEADER_SIZE",
"RESPONSE_TYPES",
"Header",
"LoginRequest",
"LoginResponse",
"CommandRequest",
"CommandResponse",
"ServerMessage",
"ServerMessageAck",
"Request",
"Response",
]
HEADER_SIZE = 8
PREFIX = "BE"
INFIX = 0xFF
class Header(NamedTuple):
"""Packet header."""
crc32: int
type: int
def __bytes__(self):
return b"".join(
(
PREFIX.encode("ascii"),
self.crc32.to_bytes(4, "little"),
INFIX.to_bytes(1, "little"),
self.type.to_bytes(1, "little"),
)
)
@classmethod
def create(cls, typ: int, payload: bytes) -> Header:
"""Create a header for the given payload."""
return cls(
crc32(
b"".join(
(INFIX.to_bytes(1, "little"), typ.to_bytes(1, "little"), payload)
)
),
typ,
)
@classmethod
def from_bytes(cls, payload: bytes) -> Header:
"""Create a header from the given bytes."""
if (size := len(payload)) != HEADER_SIZE:
raise ValueError("Invalid payload size", size)
if (prefix := payload[:2].decode("ascii")) != PREFIX:
raise ValueError("Invalid prefix", prefix)
if (infix := int.from_bytes(payload[6:7], "little")) != INFIX:
raise ValueError("Invalid infix", infix)
return cls(
int.from_bytes(payload[2:6], "little"),
int.from_bytes(payload[7:8], "little"),
)
class LoginRequest(str):
"""Login request packet."""
def __bytes__(self):
return bytes(self.header) + self.payload
@property
def payload(self) -> bytes:
"""Return the payload."""
return self.encode("ascii")
@property
def header(self) -> Header:
"""Return the appropriate header."""
return Header.create(0x00, self.payload)
class LoginResponse(NamedTuple):
"""A login response."""
header: Header
success: bool
@classmethod
def from_bytes(cls, header: Header, payload: bytes) -> LoginResponse:
"""Create a login response from the given bytes."""
return cls(header, bool(int.from_bytes(payload[:1], "little")))
class CommandRequest(NamedTuple):
"""Command packet."""
seq: int
command: str
def __bytes__(self):
return bytes(self.header) + self.payload
@property
def payload(self) -> bytes:
"""Return the payload."""
return b"".join((self.seq.to_bytes(1, "little"), self.command.encode("ascii")))
@property
def header(self) -> Header:
"""Return the appropriate header."""
return Header.create(0x01, self.payload)
@classmethod
def from_string(cls, command: str) -> CommandRequest:
"""Create a command packet from the given string."""
return cls(0x00, command)
@classmethod
def from_command(cls, command: str, *args: str) -> CommandRequest:
"""Create a command packet from the command and arguments."""
return cls.from_string(" ".join([command, *args]))
class CommandResponse(NamedTuple):
"""A command response."""
header: Header
seq: int
payload: bytes
@classmethod
def from_bytes(cls, header: Header, payload: bytes) -> CommandResponse:
"""Create a command response from the given bytes."""
return cls(header, int.from_bytes(payload[:1], "little"), payload[1:])
@property
def message(self) -> str:
"""Return the text message."""
return self.payload.decode("ascii")
class ServerMessage(NamedTuple):
"""A message from the server."""
header: Header
seq: int
payload: bytes
@classmethod
def from_bytes(cls, header: Header, payload: bytes) -> ServerMessage:
"""Create a server message from the given bytes."""
return cls(header, int.from_bytes(payload[:1], "little"), payload[1:])
@property
def message(self) -> str:
"""Return the text message."""
return self.payload.decode("ascii")
class ServerMessageAck(NamedTuple):
"""An acknowledgement of a message from the server."""
seq: int
def __bytes__(self):
return bytes(self.header) + self.payload
@property
def header(self) -> Header:
"""Return the appropriate header."""
return Header.create(0x02, self.payload)
@property
def payload(self) -> bytes:
"""Return the payload."""
return self.seq.to_bytes(1, "little")
Request = LoginRequest | CommandRequest | ServerMessageAck
Response = LoginResponse | CommandResponse | ServerMessage
RESPONSE_TYPES = {0x00: LoginResponse, 0x01: CommandResponse, 0x02: ServerMessage}
|
