import logging
import validate
import os
import CryptoBoxExceptions
try:
	import configobj	## needed for reading and writing of the config file
except:
	raise CryptoBoxExceptions.CBEnvironmentError("couldn't import 'configobj'! Try 'apt-get install python-configobj'.")


class CryptoBoxSettings:

	CONF_LOCATIONS = [
		"./cryptobox.conf",
		"~/.cryptobox.conf",
		"/etc/cryptobox/cryptobox.conf"]


	def __init__(self, config_file=None):
		self.log = logging.getLogger("CryptoBox")
		config_file = self.__getConfigFileName(config_file)
		self.log.info("loading config file: %s" % config_file)
		self.prefs = self.__getPreferences(config_file)
		self.__validateConfig()
		self.__configureLogHandler()
		self.__checkUnknownPreferences()
		self.nameDB = self.__getNameDatabase()
	

	def __getitem__(self, key):
		"""redirect all requests to the 'prefs' attribute"""
		return self.prefs[key]


	def __getPreferences(self, config_file):
		import StringIO
		config_rules = StringIO.StringIO(self.validation_spec)
		try:
			prefs = configobj.ConfigObj(config_file, configspec=config_rules)
			if prefs:
				self.log.info("found config: %s" % prefs.items())
			else: 
				raise CryptoBoxExceptions.CBConfigUnavailableError("failed to load the config file: %s" % config_file)
		except IOError:
			raise CryptoBoxExceptions.CBConfigUnavailableError("unable to open the config file: %s" % config_file)
		return prefs


	def __validateConfig(self):
		result = self.prefs.validate(CryptoBoxSettingsValidator(), preserve_errors=True)
		error_list = configobj.flatten_errors(self.prefs, result)
		if not error_list: return
		errorMsgs = []
		for sections, key, text in error_list:
			section_name = "->".join(sections)
			if not text:
				errorMsg = "undefined configuration value (%s) in section '%s'" % (key, section_name)
			else:
				errorMsg = "invalid configuration value (%s) in section '%s': %s" % (key, section_name, text)
			errorMsgs.append(errorMsg)
		raise CryptoBoxExceptions.CBConfigError, "\n".join(errorMsgs)


	def __checkUnknownPreferences(self):
		import StringIO
		config_rules = configobj.ConfigObj(StringIO.StringIO(self.validation_spec), list_values=False)
		self.__recursiveConfigSectionCheck("", self.prefs, config_rules)
		
	
	def __recursiveConfigSectionCheck(self, section_path, section_config, section_rules):
		"""should be called by '__checkUnknownPreferences' for every section
		sends a warning message to the logger for every undefined (see validation_spec)
		configuration setting
		"""
		for e in section_config.keys():
			element_path = section_path + e
			if e in section_rules.keys():
				if isinstance(section_config[e], configobj.Section):
					if isinstance(section_rules[e], configobj.Section):
						self.__recursiveConfigSectionCheck(element_path + "->", section_config[e], section_rules[e])
					else:
						self.log.warn("configuration setting should be a value instead of a section name: %s" % element_path)
				else:
					if not isinstance(section_rules[e], configobj.Section):
						pass	# good - the setting is valid
					else:
						self.log.warn("configuration setting should be a section name instead of a value: %s" % element_path)
			else:
				self.log.warn("unknown configuration setting: %s" % element_path)


	def __getNameDatabase(self):
		try:
			try:
				nameDB_file = self.prefs["Locations"]["NameDatabase"]
			except KeyError:
				raise CryptoBoxExceptions.CBConfigUndefinedError("Locations", "NameDatabase")
		except SyntaxError:
			raise CryptoBoxExceptions.CBConfigInvalidValueError("Locations", "NameDatabase", nameDB_file, "failed to interprete the filename of the name database correctly")
		## create nameDB is necessary
		if os.path.exists(nameDB_file):
			nameDB = configobj.ConfigObj(nameDB_file)
		else:
			nameDB = configobj.ConfigObj(nameDB_file, create_empty=True)
		## check if nameDB file was created successfully?
		if not os.path.exists(nameDB_file):
			raise CryptoBoxExceptions.CBEnvironmentError("failed to create name database (%s)" % nameDB_file)
		return nameDB


	def __getConfigFileName(self, config_file):
		# search for the configuration file
		import types
		if config_file is None:
			# no config file was specified - we will look for it in the ususal locations
			conf_file_list = [os.path.expanduser(f)
				for f in self.CONF_LOCATIONS
				if os.path.exists(os.path.expanduser(f))]
			if not conf_file_list:
				# no possible config file found in the usual locations
				raise CryptoBoxExceptions.CBConfigUnavailableError()
			config_file = conf_file_list[0]
		else:
			# a config file was specified (e.g. via command line)
			if type(config_file) != types.StringType:
				raise CryptoBoxExceptions.CBConfigUnavailableError("invalid config file specified: %s" % config_file)
			if not os.path.exists(config_file):
				raise CryptoBoxExceptions.CBConfigUnavailableError("could not find the specified configuration file (%s)" % config_file)
		return config_file


	def __configureLogHandler(self):
		try:
			log_level = self.prefs["Log"]["Level"].upper()
			log_level_avail = ["DEBUG", "INFO", "WARN", "ERROR"]
			if not log_level in log_level_avail:
				raise TypeError
		except KeyError:
			raise CryptoBoxExceptions.CBConfigUndefinedError("Log", "Level")
		except TypeError:
			raise CryptoBoxExceptions.CBConfigInvalidValueError("Log", "Level", log_level, "invalid log level: only %s are allowed" % log_level_avail)
		try:
			try:
				log_handler = logging.FileHandler(self.prefs["Log"]["Details"])
			except KeyError:
				raise CryptoBoxExceptions.CBConfigUndefinedError("Log", "Details")
		except IOError:
			raise CryptoBoxExceptions.CBEnvironmentError("could not create the log file (%s)" % self.prefs["Log"]["Details"])
		log_handler.setFormatter(logging.Formatter('%(asctime)s %(module)s %(levelname)s: %(message)s'))
		cbox_log = logging.getLogger("CryptoBox")
		## remove previous handlers
		cbox_log.handlers = []
		## add new one
		cbox_log.addHandler(log_handler)
		## do not call parent's handlers
		cbox_log.propagate = False
		## 'log_level' is a string -> use 'getattr'
		cbox_log.setLevel(getattr(logging,log_level))
		## the logger named "CryptoBox" is configured now


	validation_spec = """
[Main]
AllowedDevices = list(min=1)
DefaultVolumePrefix = string(min=1)
DefaultCipher = string(default="aes-cbc-essiv:sha256")
ConfigVolumeLabel = string(min=1,default="cbox_config")

[Locations]
MountParentDir = directoryExists(default="/var/cache/cryptobox/mnt")
NameDatabase = fileWriteable(default="/var/cache/cryptobox/volumen_names.db")
TemplateDir = directoryExists(default="/usr/share/cryptobox/template")
LangDir = directoryExists(default="/usr/share/cryptobox/lang")
DocDir = directoryExists(default="/usr/share/doc/cryptobox/html")
PluginDir = directoryExists(default="/usr/share/cryptobox/plugins")

[Log]
Level = option("debug", "info", "warn", "error", default="warn")
Destination = option("file", default="file")
Details = string(min=1)

[WebSettings]
Stylesheet = string(min=1)
Language = string(min=1, default="en")
DocLanguage = string(min=1, default="en")

[Programs]
cryptsetup = fileExecutable(default="/sbin/cryptsetup")
mkfs-data = fileExecutable(default="/sbin/mkfs.ext3")
blkid = fileExecutable(default="/sbin/blkid")
mount = fileExecutable(default="/bin/mount")
umount = fileExecutable(default="/bin/umount")
super = fileExecutable(default="/usr/bin/super")
# this is the "program" name as defined in /etc/super.tab
CryptoBoxRootActions = string(min=1)
		"""



class CryptoBoxSettingsValidator(validate.Validator):

	def __init__(self):
		validate.Validator.__init__(self)
		self.functions["directoryExists"] = self.check_directoryExists
		self.functions["fileExecutable"] = self.check_fileExecutable
		self.functions["fileWriteable"] = self.check_fileWriteable
	

	def check_directoryExists(self, value):
		dir_path = os.path.abspath(value)
		if not os.path.isdir(dir_path):
			raise validate.VdtValueError("%s (not found)" % value)
		if not os.access(dir_path, os.X_OK):
			raise validate.VdtValueError("%s (access denied)" % value)
		return dir_path
	

	def check_fileExecutable(self, value):
		file_path = os.path.abspath(value)
		if not os.path.isfile(file_path):
			raise validate.VdtValueError("%s (not found)" % value)
		if not os.access(file_path, os.X_OK):
			raise validate.VdtValueError("%s (access denied)" % value)
		return file_path
	

	def check_fileWriteable(self, value):
		file_path = os.path.abspath(value)
		if os.path.isfile(file_path):
			if not os.access(file_path, os.W_OK):
				raise validate.VdtValueError("%s (not found)" % value)
		else:
			parent_dir = os.path.dirname(file_path)
			if os.path.isdir(parent_dir) and os.access(parent_dir, os.W_OK):
				return file_path
			raise validate.VdtValueError("%s (directory does not exist)" % value)
		return file_path