import fcntl
from collections.abc import Generator
from contextlib import contextmanager
from pathlib import Path


@contextmanager
def locked_open(filename: str | Path, mode: str = "r") -> Generator:
    """
    This is a context manager that provides an advisory write lock on the file specified by `filename` when entering the context, and releases the lock when leaving the context. The lock is acquired using the `fcntl` module's `LOCK_EX` flag, which applies an exclusive write lock to the file.
    """
    with open(filename, mode) as fd:
        fcntl.flock(fd, fcntl.LOCK_EX)
        yield fd
        fcntl.flock(fd, fcntl.LOCK_UN)