"""异步业务字段存储接口；字段值保留 bool/int/str 的区别。"""

from typing import Protocol


class CheckpointNotFoundError(Exception):
    """存储适配器明确确认线程不存在。"""


class SessionRepository(Protocol):
    async def load(self, session_id: str) -> dict:
        """读取业务字段；不存在返回空 dict。"""
        ...

    async def apply_update(self, session_id: str, patch: dict) -> dict:
        """提交差量后返回完整业务字段。"""
        ...

    async def delete(self, session_id: str) -> None:
        """幂等删除；真实存储错误必须传播。"""
        ...


class InMemorySessionRepository:
    def __init__(self):
        self._store: dict[str, dict] = {}

    async def load(self, session_id: str) -> dict:
        return dict(self._store.get(session_id) or {})

    async def apply_update(self, session_id: str, patch: dict) -> dict:
        state = self._store.setdefault(session_id, {})
        state.update(patch)
        return dict(state)

    async def delete(self, session_id: str) -> None:
        self._store.pop(session_id, None)


__all__ = ["CheckpointNotFoundError", "SessionRepository", "InMemorySessionRepository"]