#!/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/>.
#

"""
Configures or runs unattended-upgrades
"""

import argparse
import os
import re
import subprocess
import sys

CONF_FILE = '/etc/apt/apt.conf.d/50unattended-upgrades'
AUTO_CONF_FILE = '/etc/apt/apt.conf.d/20auto-upgrades'
LOCK_FILE = '/var/lib/dpkg/lock'
LOG_FILE = '/var/log/unattended-upgrades/unattended-upgrades.log'


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('run', help='Upgrade packages on the system')
    subparsers.add_parser('check-auto',
                          help='Check if automatic upgrades are enabled')
    subparsers.add_parser('enable-auto', help='Enable automatic upgrades')
    subparsers.add_parser('disable-auto', help='Disable automatic upgrades.')
    subparsers.add_parser('is-package-manager-busy',
                          help='Return whether package manager is busy')
    subparsers.add_parser('get-log', help='Print the automatic upgrades log')

    return parser.parse_args()


def subcommand_run(_):
    """Run unattended-upgrades"""
    try:
        setup()
    except FileNotFoundError:
        print('Error: Could not configure unattended-upgrades.',
              file=sys.stderr)
        sys.exit(1)

    try:
        subprocess.Popen(
            ['unattended-upgrades', '-v'],
            stdin=subprocess.DEVNULL, stdout=subprocess.DEVNULL,
            stderr=subprocess.DEVNULL, close_fds=True,
            start_new_session=True)
    except FileNotFoundError:
        print('Error: unattended-upgrades is not available.', file=sys.stderr)
        sys.exit(2)
    except Exception as error:
        print('Error: {0}'.format(error), file=sys.stderr)
        sys.exit(3)


def subcommand_check_auto(_):
    """Check if automatic upgrades are enabled"""
    arguments = ['apt-config', 'shell', 'UpdateInterval',
                 'APT::Periodic::Update-Package-Lists']
    try:
        output = subprocess.check_output(arguments).decode()
    except subprocess.CalledProcessError as error:
        print('Error: {0}'.format(error), file=sys.stderr)
        sys.exit(1)

    update_interval = 0
    match = re.match(r"UpdateInterval='(.*)'", output)
    if match:
        update_interval = int(match.group(1))

    print(bool(update_interval))


def subcommand_enable_auto(_):
    """Enable automatic upgrades"""
    try:
        setup()
    except FileNotFoundError:
        print('Error: Could not configure unattended-upgrades.',
              file=sys.stderr)
        sys.exit(1)

    with open(AUTO_CONF_FILE, 'w') as conffile:
        conffile.write('APT::Periodic::Update-Package-Lists "1";\n')
        conffile.write('APT::Periodic::Unattended-Upgrade "1";\n')


def subcommand_disable_auto(_):
    """Disable automatic upgrades"""
    try:
        os.rename(AUTO_CONF_FILE, AUTO_CONF_FILE + '.disabled')
    except FileNotFoundError:
        print('Already disabled.')


def setup():
    """Sets unattended-upgrades config to upgrade any package from Debian."""
    with open(CONF_FILE, 'r') as conffile:
        lines = conffile.readlines()

    for line in lines:
        if re.match(r'\s*"o(rigin)?=Debian";', line):
            return  # already configured

    with open(CONF_FILE, 'w') as conffile:
        for line in lines:
            conffile.write(line)
            if re.match(r'\s*Unattended-Upgrade::Origins-Pattern\s+{', line):
                conffile.write('        "origin=Debian";\n')


def subcommand_is_package_manager_busy(_):
    """Return whether package manager is busy."""
    try:
        subprocess.check_output(['lsof', LOCK_FILE])
    except subprocess.CalledProcessError:
        sys.exit(-1)


def subcommand_get_log(_):
    """Print the automatic upgrades log."""
    try:
        with open(LOG_FILE, 'r') as file_handle:
            print(file_handle.read())
    except IOError:
        pass


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()