"""JSON file persistence backend for StateManager."""

import json
from pathlib import Path
from typing import Any

from fusionagi.schemas.task import Task, TaskState
from fusionagi.core.persistence import StateBackend
from fusionagi._logger import logger


class JsonFileBackend(StateBackend):
    """
    StateBackend that persists tasks and traces to a JSON file.

    Use with StateManager(backend=JsonFileBackend(path="state.json")).
    File is created on first write; directory must exist or be creatable.
    """

    def __init__(self, path: str | Path) -> None:
        self._path = Path(path)
        self._tasks: dict[str, dict[str, Any]] = {}
        self._traces: dict[str, list[dict[str, Any]]] = {}
        self._load()

    def _load(self) -> None:
        if not self._path.exists():
            return
        try:
            data = json.loads(self._path.read_text(encoding="utf-8"))
            self._tasks = data.get("tasks", {})
            self._traces = data.get("traces", {})
        except Exception as e:
            logger.warning("JsonFileBackend load failed", extra={"path": str(self._path), "error": str(e)})

    def _save(self) -> None:
        self._path.parent.mkdir(parents=True, exist_ok=True)
        data = {"tasks": self._tasks, "traces": self._traces}
        self._path.write_text(json.dumps(data, indent=2), encoding="utf-8")

    def get_task(self, task_id: str) -> Task | None:
        raw = self._tasks.get(task_id)
        if raw is None:
            return None
        try:
            return Task.model_validate(raw)
        except Exception:
            return None

    def set_task(self, task: Task) -> None:
        self._tasks[task.task_id] = task.model_dump(mode="json")
        self._save()

    def get_task_state(self, task_id: str) -> TaskState | None:
        task = self.get_task(task_id)
        return task.state if task else None

    def set_task_state(self, task_id: str, state: TaskState) -> None:
        task = self.get_task(task_id)
        if task:
            updated = task.model_copy(update={"state": state})
            self.set_task(updated)

    def append_trace(self, task_id: str, entry: dict[str, Any]) -> None:
        self._traces.setdefault(task_id, []).append(entry)
        self._save()

    def get_trace(self, task_id: str) -> list[dict[str, Any]]:
        return list(self._traces.get(task_id, []))