"""Optional persistence interface for state manager; in-memory is default."""

from abc import ABC, abstractmethod
from typing import Any

from fusionagi.schemas.task import Task, TaskState


class StateBackend(ABC):
    """
    Abstract backend for task state and traces; replace StateManager internals for persistence.
    Any backend used to replace StateManager storage must implement get_task_state and set_task_state
    in addition to task and trace methods.
    """

    @abstractmethod
    def get_task(self, task_id: str) -> Task | None:
        """Load task by id."""
        ...

    @abstractmethod
    def set_task(self, task: Task) -> None:
        """Save task."""
        ...

    @abstractmethod
    def get_task_state(self, task_id: str) -> TaskState | None:
        """Return current task state or None if task unknown."""
        ...

    @abstractmethod
    def set_task_state(self, task_id: str, state: TaskState) -> None:
        """Update task state; creates no task if missing."""
        ...

    @abstractmethod
    def append_trace(self, task_id: str, entry: dict[str, Any]) -> None:
        """Append trace entry."""
        ...

    @abstractmethod
    def get_trace(self, task_id: str) -> list[dict[str, Any]]:
        """Load trace for task."""
        ...