#!/usr/bin/env python

import os, sys, re, logging, signal, time, threading

ROOT = '/q/public/mdnsexporter'
HOSTNAME = 'fleet'
SVC_PATH = '/etc/avahi/services'
QUIT = False
PID_FILE = os.path.join(ROOT, 'var', 'mdnsexporter.pid')
LOG_FILE = os.path.join(ROOT, 'log', 'mdnsexporter.log')

logging.basicConfig(
    level=logging.DEBUG,
    format='%(asctime)s %(levelname)s %(message)s',
    filename=LOG_FILE,
    filemode='a'
)

def handler(signum, sigframe):
    if os.path.exists(PID_FILE):
        os.unlink(PID_FILE)
        globals()['QUIT'] = True

signal.signal(signal.SIGTERM, handler)
signal.signal(signal.SIGINT, handler)

class DNSSDRunner(threading.Thread):
    def __init__(self, file, svc):
        self.svc_name, self.svc_type, self.svc_port, self.svc_text = svc
        self.file = file
        threading.Thread.__init__(self)

    def run(self):
        pid = os.fork()
        if pid:
            while not QUIT and self.file in svcs().keys():
                time.sleep(1)
                pass
            logging.info('killing %s' % self.file)
            os.kill(pid, 15)
        else:
            os.execlp(
                'dns-sd', 'dns-sd', '-R',
                '"%s"' % self.svc_name,
                self.svc_type,
                '.',
                self.svc_port,
                self.svc_text,
            )

def svcs():
    svcs = {}
    for file in os.listdir(SVC_PATH):
        try:
            data = open(os.path.join(SVC_PATH, file), 'r').read()

            m = re.search(r'<name[^>]*>(.*?)</name>', data)
            svc_name = m.group(1)

            if '%h' in svc_name:
                svc_name = svc_name.replace('%h', HOSTNAME)

            m = re.search(r'<type>(.*?)</type>', data)
            svc_type = m.group(1)

            m = re.search(r'<port>(.*?)</port>', data)
            svc_port = m.group(1)

            m = re.search(r'<txt-record>(.*?)</txt-record>', data)
            svc_text = m.group(1)

            svcs[file] = (svc_name, svc_type, svc_port, svc_text)
        except:
            pass

    return svcs

threads = []
spawned = {}

pid = os.fork()
if pid:
    sys.exit(0)

os.chdir('/')
os.setsid()
os.umask(0)

pid = os.fork()
if pid:
    sys.exit(0)

open(PID_FILE, 'w').write(str(os.getpid()))
while not QUIT:
    sv = svcs()
    delete = []
    for sp_file, sp_svc in spawned.iteritems():
        if sp_file not in sv.keys():
            delete.append(sp_file)

    for d in delete:
        logging.debug('removing %s' % d)
        del spawned[d]

    for file, svc in sv.iteritems():
        svc_name, svc_type, svc_port, svc_text = svc

        if file not in spawned.keys():
            logging.info('spawning %s' % svc_name)
            t = DNSSDRunner(file, svc)
            t.start()
            threads.append(t)
            spawned[file] = svc

    time.sleep(1)

logging.info('quitting')
for t in threads:
    t.join()