"""Backend package facade: native Periscope + inherited PinScope.

``periscope/src/backend`` and ``periscope/dependency/backend`` are merged via
pkgutil path extension. Do not put application modules in this directory.
"""
from __future__ import annotations

import sys
from pathlib import Path
from pkgutil import extend_path

_REPO = Path(__file__).resolve().parents[1]
_SRC = _REPO / "periscope" / "src"
_DEP = _REPO / "periscope" / "dependency"
# Last insert is searched first: native src overlays inherited dependency.
for _p in (_DEP, _SRC):
    _s = str(_p)
    if not _p.is_dir():
        continue
    if _s in sys.path:
        sys.path.remove(_s)
    sys.path.insert(0, _s)


def _prefer_native_backend(paths: list[str]) -> list[str]:
    src, other, dep = [], [], []
    for p in paths:
        norm = p.replace("\\", "/")
        if "/periscope/src/" in norm:
            src.append(p)
        elif "/periscope/dependency/" in norm:
            dep.append(p)
        else:
            other.append(p)
    return src + other + dep


__path__ = _prefer_native_backend(list(extend_path(__path__, __name__)))