from typing import Any, Callable, List, TypeVar
from enum import Enum
from dataclasses import dataclass

class EventType(Enum):
  MESSAGE = 1
  MENTION = 2

class MetaEvent():
  def __new__(metacls, name, bases, namespace, **kwargs):
    return super().__new__(metacls, name, bases, namespace)

  def __init__(cls, name, bases, namespace, event_types: List[EventType]=[], **kwargs):
    cls.event_types = event_types
    super().__init__(name, bases, namespace)

class EventBase:
  pass

@dataclass
class RoomEvent(EventBase):
  room_id: int
  room_name: int

@dataclass
class MessageEvent(RoomEvent, metaclass=MetaEvent, event_types=[EventType.MESSAGE]):
  content: str
  message_id: int
  user_id: int
  user_name: str

@dataclass
class MentionEvent(MessageEvent, metaclass=MetaEvent, event_types=[EventType.MENTION]):
  parent_id: int
  target_user_id: int

EventHandler = Callable[[Any], None]

T = TypeVar("T", bound=EventBase)

class Room:
  def __init__(self):
    self._handlers: dict[EventType, set[EventHandler]] = {
      eventType: set() for eventType in EventType
    }
    self.add_handler(MentionEvent, self._mentionHandler)

  def add_handler(self, cls: T, handler: Callable[[T], None]):
    for event_type in cls.event_types:
      self._handlers[event_type].add(handler)

  def _mentionHandler(e: MentionEvent):
    pass