"""Small atomic JSON store for a single-process LibBee deployment."""

import copy
import json
import os
import tempfile
import time
from pathlib import Path
from typing import Any, Dict, Optional


class JsonRuntimeStore:
    def __init__(self, path: Path, default: Optional[Dict[str, Any]] = None):
        self.path = Path(path)
        self.path.parent.mkdir(parents=True, exist_ok=True)
        self.default = copy.deepcopy(default or {})

    def load(self) -> Dict[str, Any]:
        data = copy.deepcopy(self.default)
        try:
            loaded = json.loads(self.path.read_text(encoding="utf-8"))
            if isinstance(loaded, dict):
                data.update(loaded)
        except (OSError, UnicodeError, json.JSONDecodeError):
            pass
        return data

    def save(self, data: Dict[str, Any]) -> None:
        """Replace a complete object with a unique, owner-only temporary file.

        A shared fixed `.tmp` name allowed independent writers to overwrite or
        unlink each other's temporary file. Unique files prevent that race;
        callers still need a database for multi-process read/modify/write use.
        """
        if not isinstance(data, dict):
            raise TypeError("runtime data must be a JSON object")
        tmp = None
        try:
            with tempfile.NamedTemporaryFile(
                mode="w", encoding="utf-8", dir=self.path.parent,
                prefix=f".{self.path.name}.", suffix=".tmp", delete=False,
            ) as handle:
                tmp = Path(handle.name)
                json.dump(data, handle, ensure_ascii=False, indent=2, allow_nan=False)
                handle.flush()
                os.fsync(handle.fileno())
            os.replace(tmp, self.path)
        finally:
            if tmp is not None:
                tmp.unlink(missing_ok=True)

    def update(self, **kwargs: Any) -> Dict[str, Any]:
        data = self.load()
        data.update(kwargs)
        data["updated_at"] = time.time()
        self.save(data)
        return data