"""OS lock shared by every SDK effect and exclusive profile activation."""

import fcntl
from contextlib import contextmanager
from pathlib import Path

ROOT = Path("/var/lib/mission-core-insta360")


@contextmanager
def acquisition(wait=False):
    path = ROOT / "lifecycle.lock"
    for item in (ROOT, path):
        info = item.lstat()
        if item.is_symlink() or info.st_uid != 0 or info.st_mode & 0o022:
            raise RuntimeError("Untrusted camera lifecycle lock")
    with path.open("rb") as handle:
        try:
            fcntl.flock(handle, fcntl.LOCK_SH | (0 if wait else fcntl.LOCK_NB))
        except BlockingIOError:
            raise RuntimeError("Подготовка драйвера ещё выполняется.") from None
        if (ROOT / "maintenance").exists():
            raise RuntimeError("Драйвер X4 обновляется. Повторите после подготовки.")
        yield