from abc import abstractmethod
import json
from typing import Dict, Type

class Message:
    MESSAGE_TYPES: Dict[str, Type['Message']] = {}

    @classmethod
    @abstractmethod
    def from_hash(cls: Type['Message'], d: Dict): pass

    @abstractmethod
    def to_hash(self) -> Dict: pass

    @classmethod
    def decode(cls: Type['Message'], raw: str):
        hash = json.loads(raw)
        tag = hash['tag']
        return cls.MESSAGE_TYPES[tag].from_hash(hash)

    def json(self) -> str:
        hash = self.to_hash()
        return json.dumps(self.to_hash())

def message(name: str):
    def decorate(class_decl: Type['Message']) -> Type['Message']:
        Message.MESSAGE_TYPES[name] = class_decl
        return class_decl
    return decorate

@message('config')
class InitialConfig(Message):
    user: str
    game: str

    def __init__(self, user: str, game: str):
        self.user = user
        self.game = game

    @classmethod
    def from_hash(cls, d: Dict):
        return cls(user=d['user'], game=d['game'])

    def to_hash(self) -> Dict:
        return {'user': self.user, 'game': self.game}

@message('post')
class Post(Message):
    author: str
    content: str

    def __init__(self, author: str, content: str):
        self.author = author
        self.content = content

    @classmethod
    def from_hash(cls, d: Dict):
        return cls(author=d['author'], content=d['content'])

    def to_hash(self) -> Dict:
        return {
            'tag': 'post',
            'author': self.author,
            'content': self.content,
        }