#!/usr/bin/python3
# -*- mode: python -*-
#
# 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 Transmission daemon.
"""

import argparse
import json
import subprocess


SERVICE_CONFIG = '/etc/default/transmission-daemon'
TRANSMISSION_CONFIG = '/etc/transmission-daemon/settings.json'


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

    # Get whether service is enabled
    subparsers.add_parser('get-enabled',
                          help='Get whether Transmission service is enabled')

    # Enable service
    subparsers.add_parser('enable', help='Enable Transmission service')

    # Disable service
    subparsers.add_parser('disable', help='Disable Transmission service')

    # Get whether daemon is running
    subparsers.add_parser('is-running',
                          help='Get whether Transmission daemon is running')

    # Get currently configured Tor hidden service information
    merge_configuration = subparsers.add_parser(
        'merge-configuration',
        help='Merge given JSON configration with existing')
    merge_configuration.add_argument(
        'configuration',
        help='JSON encoded configuration to merge')

    return parser.parse_args()


def subcommand_get_enabled(_):
    """Get whether Transmission service is enabled."""
    try:
        with open(SERVICE_CONFIG, 'r') as file_handle:
            for line in file_handle:
                if line.startswith('ENABLE_DAEMON'):
                    value = line.split('=')[1].strip()
                    print('yes' if int(value) else 'no')
                    return
    except IOError:
        pass

    print('no')


def subcommand_enable(_):
    """Start Transmission service."""
    set_service_enable(enable=True)
    subprocess.call(['service', 'transmission-daemon', 'start'])
    subprocess.call(['a2enconf', 'transmission-plinth'])
    subprocess.call(['service', 'apache2', 'reload'])


def subcommand_disable(_):
    """Stop Transmission service."""
    subprocess.call(['a2disconf', 'transmission-plinth'])
    subprocess.call(['service', 'apache2', 'reload'])
    subprocess.call(['service', 'transmission-daemon', 'stop'])
    set_service_enable(enable=False)


def set_service_enable(enable):
    """Enable/disable Transmission daemon; enable: boolean."""
    newline = 'ENABLE_DAEMON=1\n' if enable else 'ENABLE_DAEMON=0\n'

    with open(SERVICE_CONFIG, 'r') as file_handle:
        lines = file_handle.readlines()
        for index, line in enumerate(lines):
            if line.startswith('ENABLE_DAEMON'):
                lines[index] = newline
                break

    with open(SERVICE_CONFIG, 'w') as file_handle:
        file_handle.writelines(lines)


def subcommand_is_running(_):
    """Get whether Transmission is running."""
    try:
        output = subprocess.check_output(['service', 'transmission-daemon',
                                          'status'])
    except subprocess.CalledProcessError:
        # If daemon is not running we get a status code != 0 and a
        # CalledProcessError
        print('no')
    else:
        running = False
        for line in output.decode().split('\n'):
            if 'Active' in line and 'running' in line:
                running = True
                break

        print('yes' if running else 'no')


def subcommand_merge_configuration(arguments):
    """Merge given JSON configuration with existing configuration."""
    configuration = arguments.configuration
    configuration = json.loads(configuration)

    current_configuration = open(TRANSMISSION_CONFIG, 'r').read()
    current_configuration = json.loads(current_configuration)

    new_configuration = current_configuration
    new_configuration.update(configuration)
    new_configuration = json.dumps(new_configuration, indent=4, sort_keys=True)

    open(TRANSMISSION_CONFIG, 'w').write(new_configuration)
    subprocess.call(['service', 'transmission-daemon', 'reload'])


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()