#!/usr/bin/python

import datetime, collectd, os.path, ipaddress

def parse_leases(lease_file):
	validKeys = ['lease', 'starts', 'ends', '}']
	leases = {}
	lease = {}
	for line in lease_file:
		tokens = line.split()

		if len(tokens) == 0 or tokens[0].startswith('#'):
			continue

		key = tokens[0].lower()

		if key in validKeys:
			if key == 'lease':
				lease = {'id' : tokens[1]}

			elif key == '}':
				if lease['id'] in leases:
					if leases[lease['id']]['ends'] < lease['ends']:
						leases[lease['id']] = lease
				else:
					leases[lease['id']] = lease

			else:
				lease[key] = tokens[2]+' '+tokens[3].rstrip(';')

	return leases

def parse_dhcpd_conf(config_file):
	subnet = {}
	subnets = {}
	for line in config_file:
		line = line.strip().rstrip(';')
		tokens = line.split()

		if len(tokens) == 0 or tokens[0].startswith('#'):
			continue
		key = tokens[0].lower()

		if key == 'subnet':
			net = ipaddress.ip_network(unicode(tokens[1]+'/'+tokens[3]))
			subnet = {'netaddr_str' : tokens[1], 'netaddr_int' : int(net.network_address), 'netmask_str' : tokens[3], 'netmask_int' : int(net.netmask)}
		
		elif key == 'interface':
			subnet['interface'] = tokens[1]

		elif key == '}':
			subnet_add(subnets, subnet)
			subnet = {}

	return subnets

def subnet_add(subnets, subnet):
	if 'interface' not in subnet:
		subnet['interface'] = 'global'
	sub_name = subnet['interface']
	if sub_name not in subnets:
		subnets[sub_name] = subnet
	else:
		pass #needs to be implemented

def count_active_leases(all_leases, now, subnets):
	count_active = 0
	count_all = 0
	subnet_counter = {}
	for interface in subnets.iterkeys():
		subnet_counter[interface] = {'count_active': 0, 'count_all': 0, 'count_touch': 0}

	for lease in all_leases.itervalues():
		addr = int(ipaddress.ip_address(unicode(lease['id'])))
		for subnet in subnets.itervalues():
			if (addr & subnet['netmask_int']) == subnet['netaddr_int']:
				subnc = subnet_counter[subnet['interface']]
				subnc['count_all'] += 1
				count_all += 1
				if timestamp_inbetween(now, lease['starts'], lease['ends']):
					subnc['count_active'] += 1
					count_active += 1
				break

	for subnet in subnet_counter.itervalues():
			subnet['count_touch'] = subnet['count_all'] - subnet['count_active']
	count_touch = count_all - count_active

	return count_active, count_touch, subnet_counter


def timestamp_inbetween(now, start, end):
	return start < now < end

def read(data=None):
	configfile = '/etc/dhcp/dhcpd.conf'
	if os.path.isfile(configfile):
		cfile = open(configfile, 'r')
		config = parse_dhcpd_conf(cfile)
		leasefile = '/var/lib/dhcp/dhcpd.leases'
		if os.path.isfile(leasefile):
			lfile = open(leasefile, 'r')
			all_leases = parse_leases(lfile)
			lfile.close()
			count_active, count_touch, subnet_counter = count_active_leases(all_leases, datetime.datetime.utcnow().strftime("%Y/%m/%d %H:%M:%S"), config)
			vl = collectd.Values(type='dhcp_leases')
			vl.plugin='dhcp'
			vl.type_instance = 'all_interfaces'
			vl.dispatch(values=[count_active, count_touch])
			for k, v in subnet_counter.iteritems():
				vl = collectd.Values(type='dhcp_leases')
				vl.plugin='dhcp'
				vl.type_instance = k
				vl.dispatch(values=[v['count_active'], v['count_touch']])
				vl = collectd.Values(type='dhcp_leases')


def write(vl, data=None):
	for i in vl.values:
		print "%s (%s): %f" % (vl.plugin, vl.type, i)

collectd.register_read(read)
collectd.register_write(write);