#!/usr/bin/python3
#
# This file is part of Plinth.
#
# 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 helper for SSH server.
"""

import argparse
import os
import pwd
import shutil
import stat
import subprocess
import sys


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

    get_keys = subparsers.add_parser('get-keys',
                                     help='Get SSH authorized keys')
    get_keys.add_argument('--username')

    set_keys = subparsers.add_parser('set-keys',
                                     help='Set SSH authorized keys')
    set_keys.add_argument('--username')
    set_keys.add_argument('--keys')

    return parser.parse_args()


def get_user_homedir(username):
    """Return the home dir of a user by looking up in password database."""
    try:
        return pwd.getpwnam(username).pw_dir
    except KeyError as exception:
        print('Username not found')
        sys.exit(1)


def subcommand_get_keys(arguments):
    """Get SSH authorized keys."""
    user = arguments.username

    path = os.path.join(get_user_homedir(user), '.ssh', 'authorized_keys')
    try:
        with open(path, 'r') as file_handle:
            print(file_handle.read())
    except FileNotFoundError:
        pass


def subcommand_set_keys(arguments):
    """Set SSH authorized keys."""
    user = arguments.username

    ssh_folder = os.path.join(get_user_homedir(user), '.ssh')
    key_file_path = os.path.join(ssh_folder, 'authorized_keys')

    subprocess.check_call(['mkhomedir_helper', user])

    if not os.path.exists(ssh_folder):
        os.makedirs(ssh_folder)
        shutil.chown(ssh_folder, user, 'users')

    with open(key_file_path, 'w') as file_handle:
        file_handle.write(arguments.keys)

    shutil.chown(key_file_path, user, 'users')
    os.chmod(key_file_path, stat.S_IRUSR | stat.S_IWUSR)


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()