#!/usr/bin/python3
#
# This file is part of FreedomBox.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program 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 Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
"""
Configuration actions for the minidlna server.
"""
import argparse
from tempfile import mkstemp
from shutil import move
import subprocess
from os import fdopen, remove, chmod, stat

import augeas
from plinth import action_utils
from plinth.utils import grep

CONFIG_PATH = '/etc/minidlna.conf'


def parse_arguments():
    """Return parsed command line arguments as dictionary."""
    parser = argparse.ArgumentParser()
    subparsers = parser.add_subparsers(dest='subcommand', help='Sub command')

    subparsers.add_parser('setup', help='Setup SSH server')

    subparsers.add_parser('get-media-dir', help='Get media directory')

    set_media_dir = subparsers.add_parser('set-media-dir',
                                          help='Set custom media directory')
    set_media_dir.add_argument('--dir')

    subparsers.required = True
    return parser.parse_args()


def subcommand_setup(arguments):
    """
    Increase inotify watches per folder to allow minidlna to
    monitor changes in large media-dirs.
    """
    aug = augeas.Augeas(
        flags=augeas.Augeas.NO_LOAD + augeas.Augeas.NO_MODL_AUTOLOAD)
    aug.set('/augeas/load/Sysctl/lens', 'Sysctl.lns')
    aug.set('/augeas/load/Sysctl/incl[last() + 1]', '/etc/sysctl.conf')
    aug.load()

    aug.set('/files/etc/sysctl.conf/fs.inotify.max_user_watches', '100000')
    aug.save()

    subprocess.run(['sysctl', '--system'], check=True)


def subcommand_get_media_dir(arguments):
    """Retrieve media directory from minidlna.conf"""
    line = grep('^media_dir=', CONFIG_PATH)

    print(line[0].split("=")[1])


def subcommand_set_media_dir(arguments):
    """Set media directory in minidlna.conf"""
    line = grep('^media_dir=', CONFIG_PATH)[0]

    new_line = 'media_dir=%s\n' % arguments.dir
    replace_in_config_file(CONFIG_PATH, line, new_line)
    if action_utils.service_is_running('minidlna'):
        action_utils.service_restart('minidlna')


def replace_in_config_file(file_path, pattern, subst):
    """
    Create a temporary minidlna.conf file,
    replace the media dir config,
    remove original one and move the temporary file.
    Preserve permissions as the original file.
    """
    temp_file, temp_file_path = mkstemp()
    with fdopen(temp_file, 'w') as new_file:
        with open(file_path) as old_file:
            for line in old_file:
                new_file.write(line.replace(pattern, subst))

    old_st_mode = stat(file_path).st_mode
    remove(file_path)
    move(temp_file_path, file_path)
    chmod(file_path, old_st_mode)


def main():
    """Parse arguments and perform all duties."""
    arguments = parse_arguments()

    subcommand = arguments.subcommand.replace('-', '_')
    subcommand_method = globals()['subcommand_' + subcommand]
    subcommand_method(arguments)


if __name__ == '__main__':
    main()