#!/usr/bin/python3
# SPDX-License-Identifier: AGPL-3.0-or-later
"""
Configuration actions for the minidlna server.
"""
import argparse
import subprocess
from os import chmod, fdopen, remove, stat
from shutil import move
from tempfile import mkstemp

import augeas

from plinth import action_utils
from plinth.utils import grep

CONFIG_PATH = '/etc/minidlna.conf'

SYSCTL_CONF = '''# This file is managed and overwritten by FreedomBox.
# Helps minidlna monitor changes in large media directories
fs.inotify.max_user_watches = 100000
'''


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 _undo_old_configuration_changes():
    """Restore /etc/sysctl.conf to before our changes.

    Older version of minidlna app in FreedomBox < 20.9 wrote to
    /etc/sysctl.conf directly. This will cause conffile prompt during upgrade
    of procps package. Undo the changes so that upgrade can happen smoothly.

    """
    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()

    key_path = '/files/etc/sysctl.conf/fs.inotify.max_user_watches'
    if aug.get(key_path) == '100000':
        aug.remove(key_path)
        aug.save()


def subcommand_setup(_):
    """
    Increase inotify watches per folder to allow minidlna to
    monitor changes in large media-dirs.
    """
    _undo_old_configuration_changes()
    with open('/etc/sysctl.d/50-freedombox-minidlna.conf', 'w',
              encoding='utf-8') as conf:
        conf.write(SYSCTL_CONF)

    subprocess.run(['systemctl', 'restart', 'systemd-sysctl'], check=True)


def subcommand_get_media_dir(_):
    """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, encoding='utf-8') 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()