#!/usr/bin/env python

import sys
import logging
import time
import ConfigParser

from binascii import hexlify


from nfc_smartcard import NFCDevice, NFCError
from brmdoor_authenticator import UidAuthenticator, YubikeyHMACAuthenthicator
import unlocker

class BrmdoorConfigError(ConfigParser.Error):
	"""
	Signifies that config has missing or bad values.
	"""
	pass

class BrmdoorConfig(object):
	"""
	Configuration parser. Holds config variables from config file.
	"""
	
	_defaults = {
		"lock_opened_secs": "5",
		"unknown_uid_timeout_secs": "5",
		"log_level": "info"
	}
	
	def __init__(self, filename):
		"""
		Parse and read config from given filename.
		
		@throws ConfigParser.Error if parsing failed
		@throws BrmdoorConfigError if some value was missing or invalid
		"""
		self.config = ConfigParser.SafeConfigParser(defaults=BrmdoorConfig._defaults)
		self.config.read(filename)
		
		self.authDbFilename = self.config.get("brmdoor", "auth_db_filename")
		self.lockOpenedSecs = self.config.getint("brmdoor", "lock_opened_secs")
		self.unknownUidTimeoutSecs = self.config.getint("brmdoor", "unknown_uid_timeout_secs")
		self.logFile = self.config.get("brmdoor", "log_file")
		self.logLevel = self.convertLoglevel(self.config.get("brmdoor", "log_level"))
		self.unlocker = self.config.get("brmdoor", "unlocker")
	
	def convertLoglevel(self, levelString):
		"""Converts string 'debug', 'info', etc. into corresponding
		logging.XXX value which is returned.
		
		@raises BrmdoorConfigError if the level is undefined
		"""
		try:
			return getattr(logging, levelString.upper())
		except AttributeError:
			raise BrmdoorConfigError("No such loglevel - %s" % levelString)

class NFCScanner(object):
	"""Thread reading data from NFC reader"""
	        
	def __init__(self, config):
		"""Create worker reading UIDs from PN53x reader.
		"""
		self.authenticator = UidAuthenticator(config.authDbFilename)
		self.hmacAuthenticator = None
		self.unknownUidTimeoutSecs = config.unknownUidTimeoutSecs
		self.lockOpenedSecs = config.lockOpenedSecs
		
		unlockerClassName = config.unlocker
		unlockerClass = getattr(unlocker, unlockerClassName)
		self.unlocker = unlockerClass(config)

	def run(self):
		"""
		Waits for a card to get into reader field. Reads its UID and
		compares to database of authorized users. Unlocks lock if
		authorized.
		"""
		self.nfc = NFCDevice()
		self.hmacAuthenticator = YubikeyHMACAuthenthicator(
			config.authDbFilename, self.nfc
		)
		#self.nfc.pollNr = 0xFF #poll indefinitely
		while True:
			try:
				uid_hex = hexlify(self.nfc.scanUID())
				logging.debug("Got UID %s", uid_hex)
				if len(uid_hex) > 0:
					self.actOnUid(uid_hex)
				else:
					#prevent busy loop if reader goes awry
					time.sleep(0.3)
			except NFCError, e:
				#this exception happens also when scanUID times out
				logging.debug("Failed to wait for RFID card: %s", e)
			except KeyboardInterrupt:
				logging.info("Exiting on keyboard interrupt")
				self.nfc.close()
				self.nfc.unload()
				self.unlocker.lock()
				sys.exit(2)
			except Exception:
				logging.exception("Exception in main unlock thread")
				
	def actOnUid(self, uid_hex):
		"""
		Do something with the UID scanned. Try to authenticate it against
		database and open lock if authorized.
		"""
		record = self.authenticator.fetchUidRecord(uid_hex)
		
		#direct UID match
		if record is not None:
			logging.info("Unlocking for UID %s", record)
			self.unlocker.unlock()
			return
		
		#test for Yubikey HMAC auth
		record = self.hmacAuthenticator.checkHMACforUID(uid_hex)
		
		if record is not None:
			logging.info("Unlocking after HMAC for UID %s", record)
			self.unlocker.unlock()
			return
		
		logging.info("Unknown UID %s", uid_hex)
		time.sleep(self.unknownUidTimeoutSecs)
		


if __name__  == "__main__":
	
	if len(sys.argv) < 2:
		print >> sys.stderr, "Syntax: brmdoor_nfc_daemon.py brmdoor_nfc.config"
		sys.exit(1)
	
	config = BrmdoorConfig(sys.argv[1])
	
	if config.logFile == "-":
		logging.basicConfig(stream=sys.stderr, level=config.logLevel,
			format="%(asctime)s %(levelname)s %(message)s [%(pathname)s:%(lineno)d]")
	else:
		logging.basicConfig(filename=config.logFile, level=config.logLevel,
			format="%(asctime)s %(levelname)s %(message)s [%(pathname)s:%(lineno)d]")
	
	nfcScanner = NFCScanner(config)
	nfcScanner.run()