from pathlib import Path
from typing import Callable

from l4d2host.fs.base import OverlayMounter
from l4d2host.process import run_command


HELPER_PATH = "/usr/local/libexec/left4me/left4me-overlay"


class KernelOverlayFSMounter(OverlayMounter):
    # Delegates the actual mount/umount syscalls to the privileged
    # left4me-overlay helper. The helper takes only the instance name and
    # rederives lowerdirs/upper/work/merged from disk; the OverlayMounter
    # ABC accepts those args for compatibility, so we extract the name
    # from the merged path's parent directory.
    def mount(
        self,
        *,
        lowerdirs: str,
        upperdir: Path,
        workdir: Path,
        merged: Path,
        on_stdout: Callable[[str], None] | None = None,
        on_stderr: Callable[[str], None] | None = None,
        passthrough: bool = False,
        should_cancel: Callable[[], bool] | None = None,
    ) -> None:
        del lowerdirs, upperdir, workdir
        run_command(
            ["sudo", "-n", HELPER_PATH, "mount", merged.parent.name],
            on_stdout=on_stdout,
            on_stderr=on_stderr,
            passthrough=passthrough,
            should_cancel=should_cancel,
        )

    def unmount(
        self,
        *,
        merged: Path,
        on_stdout: Callable[[str], None] | None = None,
        on_stderr: Callable[[str], None] | None = None,
        passthrough: bool = False,
        should_cancel: Callable[[], bool] | None = None,
    ) -> None:
        run_command(
            ["sudo", "-n", HELPER_PATH, "umount", merged.parent.name],
            on_stdout=on_stdout,
            on_stderr=on_stderr,
            passthrough=passthrough,
            should_cancel=should_cancel,
        )