import asyncio
from contextlib import asynccontextmanager
from pathlib import Path
from typing import Generic, TypeVar

from pydantic import BaseModel, ValidationError

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


class DataManager(Generic[T]):
    def __init__(self, cls: type[T], fp: Path) -> None:
        self.cls = cls
        self.fp = fp
        self._aio_lock = asyncio.Lock()
        self._data: T | None = None

    def load(self) -> T:
        if not self.fp.exists():
            return self.cls()
        try:
            return self.cls.model_validate_json(self.fp.read_text("utf-8"))
        except ValidationError:
            return self.cls()

    def save(self, data: T):
        self.fp.write_text(data.model_dump_json(), "utf-8")

    @asynccontextmanager
    async def get_data(self):
        await self._aio_lock.acquire()
        self._data = self.load()
        yield self._data
        self.save(self._data)
        self._data = None
        self._aio_lock.release()