"""Algorithm interface. Concrete PPO / residual / hierarchical details later."""

from __future__ import annotations

from abc import ABC, abstractmethod
from typing import Any


class Algorithm(ABC):
    """Train or roll out a policy against an Isaac Lab vec env."""

    @abstractmethod
    def train(self, env: Any, log_dir: str) -> None:
        """Run learning. ``env`` is already wrapped for the library."""

    @abstractmethod
    def load(self, checkpoint: str) -> None:
        """Load weights."""

    @abstractmethod
    def act(self, obs: Any) -> Any:
        """Return actions for a batch of observations."""