#!/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 re
import shutil
import stat
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_key = subparsers.add_parser('get-key', help='Get SSH authorized key')
    get_key.add_argument('--username')

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

    return parser.parse_args()


def subcommand_get_key(arguments):
    """Get SSH authorized key."""
    user = arguments.username
    if not re.match(r'^[a-z][-a-z0-9_]*$', user):
        print('Bad username')
        sys.exit(-1)

    home = '/home/' + user
    ssh_folder = home + '/.ssh'
    keyfile_path = ssh_folder + '/authorized_keys'

    if not os.path.exists(keyfile_path):
        return

    with open(keyfile_path, 'r') as keyfile:
        key = keyfile.read()

    print(key)


def subcommand_set_key(arguments):
    """Set SSH authorized key."""
    user = arguments.username
    if not re.match(r'^[a-z][-a-z0-9_]*$', user):
        print('Bad username')
        sys.exit(-1)

    home = '/home/' + user
    ssh_folder = home + '/.ssh'
    keyfile_path = ssh_folder + '/authorized_keys'

    if not os.path.exists(home):
        shutil.copytree('/etc/skel', home)
        shutil.chown(home, user, 'users')
        for root, dirs, files in os.walk(home):
            for directory in dirs:
                shutil.chown(os.path.join(root, directory), user, 'users')
            for filename in files:
                shutil.chown(os.path.join(root, filename), user, 'users')

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

    with open(keyfile_path, 'w') as keyfile:
        keyfile.write(arguments.key)
    shutil.chown(keyfile_path, user, 'users')
    os.chmod(keyfile_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()