# This file is part of Gajim.
#
# Gajim 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.
#
# Gajim 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 Gajim. If not, see <http://www.gnu.org/licenses/>.

from gi.repository import Gio, GObject

'''
https://discourse.gnome.org/t/gtk-threading-problem-with-glib-idle-add/13597/5
https://github.com/gdm-settings/gdm-settings/blob/f245d3000200fa6be2a35c7f6ac45b131dadb5d6/src/utils.py#L116..L162
'''


class BackgroundTask(GObject.Object):
    __gtype_name__ = 'BackgroundTask'

    def __init__(self, function, finish_callback, **kwargs):
        super().__init__(**kwargs)

        self.function = function
        self.finish_callback = finish_callback
        self._current = None

    def start(self):
        if self._current:
            AlreadyRunningError('Task is already running')

        finish_callback = lambda self, task, nothing: self.finish_callback()

        task = Gio.Task.new(self, None, finish_callback, None)
        task.run_in_thread(self._thread_cb)

        self._current = task

    @staticmethod
    def _thread_cb(task, self, task_data, cancellable):
        try:
            retval = self.function()
            task.return_value(retval)
        except Exception as e:
            task.return_value(e)

    def finish(self):
        task = self._current
        self._current = None

        if not Gio.Task.is_valid(task, self):
            raise InvalidGioTaskError()

        value = task.propagate_value().value

        if isinstance(value, Exception):
            raise value

        return value