# -*- coding: utf-8 -*-
# input-remapper - GUI for device specific keyboard mappings
# Copyright (C) 2025 sezanzeb <b8x45ygc9@mozmail.com>
#
# This file is part of input-remapper.
#
# input-remapper is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# input-remapper is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with input-remapper.  If not, see <https://www.gnu.org/licenses/>.

"""A fallback backend used when no focus detection is possible.

This is selected for example on GNOME-Wayland, where the focused window cannot
be queried without a shell extension. The feature is effectively inactive, but
the focus-service still runs and reports a clear status.
"""

from __future__ import annotations

from typing import Optional

from inputremapper.focus.focus_backend import FocusBackend, FocusEvent, OnFocus
from inputremapper.logging.logger import logger


class NullBackend(FocusBackend):
    """Does nothing. Always available as the last-resort fallback."""

    name = "null"

    @staticmethod
    def is_available() -> bool:
        return True

    def start(self, on_focus: OnFocus) -> None:
        logger.warning(
            "No supported focus detection is available for this session "
            "(GNOME-Wayland is not supported). Focus-driven preset binding is "
            "inactive."
        )

    def stop(self) -> None:
        pass

    def get_current(self) -> Optional[FocusEvent]:
        return None