"""Small process-local cache for static character and prompt files only."""

from collections import OrderedDict
from copy import deepcopy
import json
from pathlib import Path
from threading import RLock

_MAX_ENTRIES = 64
_CACHE = OrderedDict()
_LOCK = RLock()


def _signature(path):
    stat = path.stat()
    return (stat.st_dev, stat.st_ino, stat.st_size, stat.st_mtime_ns, stat.st_ctime_ns)


def _load(path, as_json):
    path = Path(path).resolve()
    key = (path, as_json)
    with _LOCK:
        # Always stat: changed or deleted files must never silently use stale data.
        signature = _signature(path)
        cached = _CACHE.get(key)
        if cached is not None and cached[0] == signature:
            _CACHE.move_to_end(key)
            value = cached[1]
        else:
            _CACHE.pop(key, None)
            text = path.read_text(encoding='utf-8')
            value = json.loads(text) if as_json else text
            # A concurrent file edit must not be cached under its older signature.
            if _signature(path) == signature:
                _CACHE[key] = (signature, value)
                while len(_CACHE) > _MAX_ENTRIES:
                    _CACHE.popitem(last=False)
        return deepcopy(value) if as_json else value


def load_static_json(path):
    """Return a private copy of parsed JSON, refreshing when file metadata changes."""
    return _load(path, as_json=True)


def load_static_text(path):
    """Return cached UTF-8 text without altering whitespace."""
    return _load(path, as_json=False)