"""Tiny JSON state store so dashboard/bot settings survive a restart.

Persists things the user configures on the dashboard — per-guild listen lists,
bot behaviour toggles, TTS controls, and the chosen STT/LLM models — to a single
JSON file so a service or container restart keeps them.

Path: ``WSAI_STATE_FILE`` env, else ``~/.config/wsai/state.json``. For a
container deployment, mount that path (or point the env at a mounted volume) to
keep the file across ``docker restart``.

Pure stdlib, thread-safe, best-effort: a read/write failure never raises into
the caller (the dashboard must keep working even if the disk is unwritable).
"""

from __future__ import annotations

import json
import logging
import os
import threading
from typing import Any

log = logging.getLogger("wsai.state")

_LOCK = threading.Lock()


def path() -> str:
    return os.environ.get("WSAI_STATE_FILE") or os.path.expanduser("~/.config/wsai/state.json")


def load() -> dict[str, Any]:
    try:
        with open(path(), encoding="utf-8") as f:
            data = json.load(f)
            return data if isinstance(data, dict) else {}
    except FileNotFoundError:
        return {}
    except Exception as exc:  # noqa: BLE001 — corrupt/unreadable state must not crash startup
        log.warning("state load failed (%s): %s", path(), exc)
        return {}


def save(state: dict[str, Any]) -> None:
    p = path()
    try:
        with _LOCK:
            os.makedirs(os.path.dirname(p), exist_ok=True)
            tmp = p + ".tmp"
            with open(tmp, "w", encoding="utf-8") as f:
                json.dump(state, f, ensure_ascii=False, indent=2)
            os.replace(tmp, p)  # atomic
    except Exception as exc:  # noqa: BLE001
        log.warning("state save failed (%s): %s", p, exc)


def patch(key: str, value: Any) -> None:
    """Read-modify-write one top-level key."""
    s = load()
    s[key] = value
    save(s)