#!/usr/bin/env python3

"""Munin plugin to monitor Kea DHCP server.

=head1 NAME

kea - monitor Kea DHCP server

=head1 APPLICABLE SYSTEMS

Systems with Kea DHCP4 or DHCP6 server running.
See https://www.isc.org/kea/ for more information.

=head1 CONFIGURATION

This shows the default configuration of this plugin. You can override
the control socket URLs. Note that you most probably need to configure
"user root" to be able to talk to Kea socket.

  [kea]
  user root
  env.url4 /run/kea/kea4-ctrl-socket
  env.url6 /run/kea/kea6-ctrl-socket

If you have Kea Control Agent running you can also use it's HTTP interface.

  [kea]
  env.url4 http://localhost:8000/
  env.url6 http://localhost:8000/

=head1 AUTHOR

Kim B. Heino <b@bbbs.net>

=head1 LICENSE

GPLv2

=head1 MAGIC MARKERS

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

=cut
"""

import json
import os
import socket
import sys
import unicodedata
import requests


def safe_label(name):
    """Return safe label name."""
    # Convert ä->a as isalpha('ä') is true
    value = unicodedata.normalize('NFKD', name)
    value = value.encode('ASCII', 'ignore').decode('utf-8')

    # Remove non-alphanumeric chars
    value = ''.join(char.lower() if char.isalnum() else '_' for char in value)

    # Add leading "_" if it starts with number
    if value[:1].isnumeric():
        return f'_{value}'
    return value


def kea_talk(url, command, ipv):
    """Send single command to Kea and return json reply."""
    try:
        if url.startswith('http'):  # HTTP to Control Agent
            response = requests.post(url, timeout=30, json={
                'command': command,
                'service': [f'dhcp{ipv}'],
            })
            data = response.json()
        else:  # Unix socket to daemon
            with socket.socket(socket.AF_UNIX, socket.SOCK_STREAM) as sock:
                sock.connect(url)
                sock.send(f'{{"command": "{command}"}}'.encode('utf-8'))
                data = json.loads(sock.recv(65535).decode('utf-8'))
    except (OSError, ValueError, TypeError):
        return {}
    if 'arguments' not in data:
        return {}
    return data


def read_data():
    """Get config and statistics from Kea."""
    subnets = {}
    stats = {}
    for ipv in (4, 6):
        # Get configuration and statistics
        url = os.getenv(f'url{ipv}', f'/run/kea/kea{ipv}-ctrl-socket')
        conf = kea_talk(url, 'config-get', ipv)
        stats[ipv] = stat = kea_talk(url, 'statistic-get-all', ipv)
        if not conf or not stat:
            continue

        # Parse subnets
        for subnet in conf['arguments'][f'Dhcp{ipv}'][f'subnet{ipv}']:
            subid = subnet['id']
            key = 'addresses' if ipv == 4 else 'nas'
            used = stat['arguments'][f'subnet[{subid}].assigned-{key}'][0][0]
            subnets[subnet['subnet']] = used

    return subnets, stats


def config(data):
    """Print plugin config."""
    subnets, stats = data
    print('multigraph kea_usage')
    print('graph_title Kea subnet usage')
    print('graph_category network')
    print('graph_vlabel leases')
    print('graph_args --lower-limit 0 --base 1000')
    for subnet in subnets:
        label = safe_label(subnet)
        print(f'{label}.label Subnet {subnet}')

    if stats[4]:
        print('multigraph kea_dhcp4_rate')
        print('graph_title Kea DCHP4 rate')
        print('graph_category network')
        print('graph_vlabel packets / ${graph_period}')
        print('graph_args --lower-limit 0 --base 1000')
        for description in ('Discover received',
                            'Offer sent',
                            'Request received',
                            'ACK sent',
                            'NAK sent'):
            label = description.split()[0].lower()
            print(f'{label}.label {description}')
            print(f'{label}.type DERIVE')
            print(f'{label}.min 0')

    if stats[6]:
        print('multigraph kea_dhcp6_rate')
        print('graph_title Kea DCHP6 rate')
        print('graph_category network')
        print('graph_vlabel packets / ${graph_period}')
        print('graph_args --lower-limit 0 --base 1000')
        for description in ('Solicit received',
                            'Renew received',
                            'Advertise sent',
                            'Request received',
                            'Reply sent'):
            label = description.split()[0].lower()
            print(f'{label}.label {description}')
            print(f'{label}.type DERIVE')
            print(f'{label}.min 0')

    if os.environ.get('MUNIN_CAP_DIRTYCONFIG') == '1':
        fetch(data)


def fetch(data):
    """Print values."""
    subnets, stats = data
    print('multigraph kea_usage')
    for subnet, used in subnets.items():
        print(f'{safe_label(subnet)}.value {used}')

    if stats[4]:
        stat = stats[4]['arguments']
        print('multigraph kea_dhcp4_rate')
        print(f'discover.value {stat["pkt4-discover-received"][0][0]}')
        print(f'offer.value {stat["pkt4-offer-sent"][0][0]}')
        print(f'request.value {stat["pkt4-request-received"][0][0]}')
        print(f'ack.value {stat["pkt4-ack-sent"][0][0]}')
        print(f'nak.value {stat["pkt4-nak-sent"][0][0]}')

    if stats[6]:
        stat = stats[6]['arguments']
        print('multigraph kea_dhcp6_rate')
        print(f'solicit.value {stat["pkt6-solicit-received"][0][0]}')
        print(f'renew.value {stat["pkt6-renew-received"][0][0]}')
        print(f'advertise.value {stat["pkt6-advertise-sent"][0][0]}')
        print(f'request.value {stat["pkt6-request-received"][0][0]}')
        print(f'reply.value {stat["pkt6-reply-sent"][0][0]}')


if __name__ == '__main__':
    if len(sys.argv) > 1 and sys.argv[1] == 'autoconf':
        print('yes' if read_data()[0] else 'no (no Kea statistics)')
    elif len(sys.argv) > 1 and sys.argv[1] == 'config':
        config(read_data())
    else:
        fetch(read_data())