from dataclasses import dataclass, field
from typing import TypeVar

from cross.attachments import Attachment
from cross.fragments import Fragment

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


class AttachmentKeeper:
    def __init__(self) -> None:
        self._map: dict[type, Attachment] = {}

    def put(self, attachment: Attachment) -> None:
        self._map[attachment.__class__] = attachment

    def get(self, cls: type[T]) -> T | None:
        instance = self._map.get(cls)
        if instance is None:
            return None
        if not isinstance(instance, cls):
            raise TypeError(f"Expected {cls.__name__}, got {type(instance).__name__}")
        return instance

    def __repr__(self) -> str:
        return f"AttachmentKeeper(_map={self._map.values()})"


@dataclass
class Post:
    id: str
    parent_id: str | None
    text: str  # utf-8 text
    attachments: AttachmentKeeper = field(default_factory=AttachmentKeeper)
    fragments: list[Fragment] = field(default_factory=list)