#!/usr/bin/env python3
import re
import subprocess
import sys
import textwrap


'''
=head1 NAME

timesync_status - monitor ntp status with systemd-timesyncd

=head1 APPLICABLE SYSTEMS

All systems using systemd-timesyncd as its NTP-client. However, this
plugin itself also needs Python 3.5+ to call subprocess.run.

=head1 CONFIGURATION

This plugin should work out-of-the-box with autoconf. It does expect
timedatectl to be on $PATH, but that should always be the case in a
normal system.

=head1 INTERPRETATION

This plugin shows a graph with one line for every NTP metric it measure.
Metrics are shown with their usual name, and are explained in their
respective info fields.

This plugin issues no warnings or critical states.

=head1 MAGIC MARKERS

 #%# family=auto
 #%# capabilities=autoconf

=head1 VERSION

1.0

=head1 AUTHOR

Bert Peters <bert@bertptrs.nl>

=head1 LICENSE

GNU General Public License v2.0 only

SPDX-License-Identifier: LGPL-2.0-only

=cut
'''


def parse_time(value):
    value = value.strip()
    if ' ' in value:
        return sum(parse_time(x) for x in value.split(' '))

    # If time is exactly zero (for example Jitter), there is no unit (suffix)
    if value == "0" or value == "-0":
        return 0

    match = re.match(r'^([+-]?[0-9.]+)([a-z]+)$', value)
    if not match:
        raise ValueError('Invalid time ' + value)

    value = float(match.group(1))
    suffix = match.group(2)

    if suffix == 'min':
        value *= 60
    elif suffix == 'ms':
        value /= 1000
    elif suffix == 'us':
        value /= 1e6

    return value


def parse_response(data):
    values = {}
    for line in data.splitlines():
        k, v = line.split(': ', 1)
        values[k.strip()] = v.strip()

    return values


def retrieve():
    result = subprocess.run(['timedatectl', 'timesync-status'], capture_output=True)
    if result.returncode != 0:
        sys.exit('timedatectl failed')

    output = result.stdout.decode('utf-8')
    values = parse_response(output)

    # If NTP server is not responding, timesync-status will not return all
    # fields, we mark these as "U"

    if 'Offset' in values:
        print('offset.value', parse_time(values['Offset']))
    else:
        print('offset.value U')

    if 'Delay' in values:
        print('delay.value', parse_time(values['Delay']))
        print('delay.extinfo', 'Server', values['Server'])
    else:
        print('delay.value U')

    if 'Jitter' in values:
        print('jitter.value', parse_time(values['Jitter']))
    else:
        print('jitter.value U')

    if 'Poll interval' in values:
        print('poll.value', parse_time(values['Poll interval'].split('(')[0]))
    else:
        print('poll.value U')


def autoconf():
    result = subprocess.run(['timedatectl', 'status'], capture_output=True)
    if result.returncode != 0:
        print('no (failed to run timedatectl)')
        return

    values = parse_response(result.stdout.decode('utf-8'))
    if values['NTP service'] == 'active':
        print('yes')
    else:
        print('no (ntp service not running)')


def config():
    print(textwrap.dedent('''\
            graph_title Timesync status
            graph_vlabel s
            graph_category time

            offset.label Offset
            offset.info Time difference between source and local

            delay.label Delay
            delay.info Roundtrip time to the NTP-server

            jitter.label Jitter
            jitter.info Difference in offset between two subsequent samples

            poll.label Polling time
            poll.info Time between two subsequent NTP-polls
    '''))


if __name__ == '__main__':
    if len(sys.argv) > 1 and sys.argv[1] == 'config':
        config()
    elif len(sys.argv) > 1 and sys.argv[1] == 'autoconf':
        autoconf()
    else:
        retrieve()