#!/usr/bin/env python

import sys, os
import getopt, syslog
import pwd, grp

import Backend, Pivot, Config

SCRIPT = "slapd-pivot"
USER = None
GROUP = None

class Log:
	def __init__(self):
		syslog.openlog('slapd-pivot')
	def write(self, string):
		string = string.encode("utf-8", "replace").strip("\n\r")
		if string:
			syslog.syslog(syslog.LOG_WARNING | syslog.LOG_DAEMON, s)
	def flush(self):
		pass


def failure(msg, details = None):
	if details:
		msg += ": " + details
	print >> sys.stderr, "%s: %s" % (SCRIPT, msg)
	sys.exit(1)


def usage():
	print >> sys.stderr, "usage: %s -f config [-d level] [-u user] [-g group]" % SCRIPT
	sys.exit(2)


def run_server():
	server = Backend.Server("/tmp/pivot-slapd.sock", Pivot.Database)
	try:
		server.serve_forever()
	except KeyboardInterrupt:
		sys.exit(0)


def drop_privileges():
	global GROUP, USER

	if GROUP:
		try:
			GROUP = int(GROUP)
		except ValueError:
			try:
				GROUP = grp.getgrgid(GROUP)[2]
			except KeyError:
				failure("invalid group: %s" % GROUP)
		os.setegid(GROUP)

	if USER:
		try:
			USER = int(USER)
		except ValueError:
			try:
				USER = pwd.getpwnam(USER)[2]
			except KeyError:
				failure("invalid user: %s" % USER)
		os.seteuid(USER)


def daemon():
	# do the UNIX double-fork magic, see Stevens' "Advanced
	# Programming in the UNIX Environment" for details (ISBN 0201563177)
	try:
		pid = os.fork()
		if pid > 0:
			# exit first parent
			sys.exit(0)
	except OSError, e:
		failure("couldn't fork to daemon", e.strerror)

	os.chdir(os.path.dirname(sys.argv[0]))

	# decouple from parent environment
	os.setsid()
	os.umask(0)

	# do second fork
	try:
		pid = os.fork()
		if pid > 0:
			# exit from second parent, print eventual PID before
			# print "Daemon PID %d" % pid
			open(PIDFILE,'w').write("%d"%pid)
			sys.exit(0)
	except OSError, e:
		failure("couldn't fork to daemon", e.strerror)

	os.chdir("/")
	sys.stderr = Log()


if __name__ == '__main__':

	daemonize = True
	config = "/usr/local/etc/slapd-pivot.conf"

	try:
		opts, args = getopt.getopt(sys.argv[1:], 'd:f:g:u:')
	except getopt.GetoptError:
		usage()

	for (opt, oarg) in opts:
		if opt == "-d":
			try:
				daemonize = False
				level = int(oarg)
				if level >= 4:
					Backend.debug = True
			except:
				failure("invalid debug level", oarg)
		elif opt == '-f':
			config = oarg

		elif opt == '-g':
			GROUP = oarg

		elif opt == '-u':
			USER = oarg

	# No extra arguments
	if args:
		usage()

	try:
		# Load up our config file
		Config.load(config)
	except Config.Error, ex:
		failure(str(ex))

	# Change to a user that was specified
	drop_privileges()

	# Become a daemon if requested
	if daemonize:
		daemon()

	# And off we go
	run_server()