"""Recognition state file — atomic JSON I/O shared by parent + child.

The dashboard (parent process) writes this file on every toggle / face
gallery change; the Gemini child (`gemini/script.py`) polls it at 1 Hz
to flip its in-memory flags without a session restart.

Format (data/.recognition_state.json):
    {
        "vision_enabled":    bool,
        "face_rec_enabled":  bool,
        "gallery_version":   int   # bumped on every face CRUD
    }
"""

from __future__ import annotations

import json
import os
import tempfile
from dataclasses import asdict, dataclass
from pathlib import Path


@dataclass
class RecognitionState:
    vision_enabled: bool = False
    face_rec_enabled: bool = False
    gallery_version: int = 0


def read(path: Path) -> RecognitionState:
    """Return the persisted state, or a default if missing/corrupt."""
    try:
        raw = json.loads(Path(path).read_text(encoding="utf-8"))
    except (FileNotFoundError, json.JSONDecodeError, OSError):
        return RecognitionState()
    return RecognitionState(
        vision_enabled=bool(raw.get("vision_enabled", False)),
        face_rec_enabled=bool(raw.get("face_rec_enabled", False)),
        gallery_version=int(raw.get("gallery_version", 0)),
    )


def write(path: Path, state: RecognitionState) -> None:
    """Write atomically via tempfile + os.replace."""
    p = Path(path)
    p.parent.mkdir(parents=True, exist_ok=True)
    fd, tmp = tempfile.mkstemp(prefix=f".{p.name}.", suffix=".tmp", dir=str(p.parent))
    try:
        with os.fdopen(fd, "w", encoding="utf-8") as fh:
            json.dump(asdict(state), fh, ensure_ascii=False, indent=2)
        os.replace(tmp, p)
    except Exception:
        try:
            os.unlink(tmp)
        except OSError:
            pass
        raise


def mutate(path: Path, **changes) -> RecognitionState:
    """Read-modify-write helper. Returns the new state."""
    cur = read(path)
    for k, v in changes.items():
        if hasattr(cur, k):
            setattr(cur, k, v)
    write(path, cur)
    return cur