"""Base engine class."""

from __future__ import annotations

import abc
from typing import Any


class BaseEngine(abc.ABC):
    """Lifecycle: lazy -> load() -> ready -> unload()."""

    name: str = "base"

    def __init__(self) -> None:
        self._loaded = False
        self._lock_count = 0
        self.last_error: str | None = None

    @property
    def loaded(self) -> bool:
        return self._loaded

    @property
    def status(self) -> str:
        if self._loaded:
            return "loaded"
        if self.last_error:
            return f"error: {self.last_error}"
        return "not_loaded"

    def load(self) -> None:
        if self._loaded:
            return
        try:
            self._do_load()
            self._loaded = True
            self.last_error = None
        except Exception as exc:
            self.last_error = str(exc)
            raise

    def unload(self) -> None:
        self._do_unload()
        self._loaded = False

    @abc.abstractmethod
    def _do_load(self) -> None: ...
    @abc.abstractmethod
    def _do_unload(self) -> None: ...

    def __repr__(self) -> str:
        return f"<{self.__class__.__name__} loaded={self._loaded}>"