"""Cached access to bundled SVG node symbols."""
from __future__ import annotations

import os

from PyQt6.QtSvg import QSvgRenderer

_NODES_DIR = os.path.join(os.path.dirname(os.path.dirname(__file__)), "resources", "nodes")
_cache: dict[str, QSvgRenderer] = {}


def nodes_dir() -> str:
    return _NODES_DIR


def renderer(svg_name: str) -> QSvgRenderer | None:
    """Return a cached, valid QSvgRenderer for ``svg_name`` or None."""
    if not svg_name:
        return None
    r = _cache.get(svg_name)
    if r is None:
        path = os.path.join(_NODES_DIR, svg_name)
        if not os.path.exists(path):
            return None
        r = QSvgRenderer(path)
        if not r.isValid():
            return None
        _cache[svg_name] = r
    return r