import os, sys
from string import Template
from subprocess import PIPE, Popen,call

BUSYBOX_BINARY = "busybox"
TEMPLATE_FILE = os.path.dirname(os.path.realpath(__file__)) + "/udhcpd.conf.template"

class VMdhcpd:
	def __init__(self, vmid ,config):
		self.__config = config
		self.__vmid = vmid

	def start(self):
		self.__kill()

		if ('VMs' in self.__config) and (self.__vmid in self.__config['VMs']):
			config = self.__config['VMs'][self.__vmid]
		else:
			raise Exception("No such VM configuration")

		if "network" in config and "ip" in config["network"]:
			config_file_str = None
			with open(TEMPLATE_FILE) as f:
				config_file_str = f.read()	
			
			template_params = {
				"ip_address" : config['network']['ip'][0],
				"interface" : config['network']['dev'],
				"pidfile" : self.__config['dhcpd']['pidfile'].replace("$VMID", self.__vmid),
				"router" : self.__config['dhcpd']['router'],
				"dns1" : self.__config['dhcpd']['dns1'],
				"dns2" : self.__config['dhcpd']['dns2']
			}

			config_file_str = Template(config_file_str).substitute(template_params)
			
			#imake sure the interface has some address as udhcpd can't use it without
			call(["ip", "addr", "replace", "dev", config['network']['dev'], "192.168.123.221/32"], stdout=open("/dev/null"))

			command = BUSYBOX_BINARY + " udhcpd -f - << EOFEOFEOF\n" + config_file_str + "\nEOFEOFEOF"
			Popen(command, stdout=open("/dev/null"), stderr=open("/dev/null"), shell=True, start_new_session=True)
			#os.system(command)


	def stop(self):
		self.__kill()

	def __kill(self):
		pid,filename = self.getPid()
		if(pid is not None):
			os.kill(pid,9)

		try:
			os.remove(filename)
		except OSError:
			pass

	def getPid(self) -> "(int or None, filname)":
		result = None
		filename = self.__config['dhcpd']['pidfile'].replace("$VMID", self.__vmid)
		try:
			with open(filename) as pidfd:
				firstline = pidfd.readline().strip()
				result = int(firstline) if firstline.isdigit() else None
		except IOError:
			pass
		return (result,filename)