#!/usr/bin/env python2
# -*- coding: utf-8 -*-
#
#  smoke_zephyr/configuration.py
#
#  Redistribution and use in source and binary forms, with or without
#  modification, are permitted provided that the following conditions are
#  met:
#
#  * Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
#  * Redistributions in binary form must reproduce the above
#    copyright notice, this list of conditions and the following disclaimer
#    in the documentation and/or other materials provided with the
#    distribution.
#  * Neither the name of the project nor the names of its
#    contributors may be used to endorse or promote products derived from
#    this software without specific prior written permission.
#
#  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
#  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
#  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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#  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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import copy
import json
import os
import sys

try:
	import yaml
except ImportError:
	has_yaml = False
	"""Whether the :py:mod:`yaml` module is available or not."""
else:
	has_yaml = True
	try:
		from yaml import CLoader as Loader, CDumper as Dumper
	except ImportError:
		from yaml import Loader, Dumper

SERIALIZER_DRIVERS = {}
"""The serializer drivers that are available."""
SERIALIZER_DRIVERS['json'] = {'load': json.load, 'dumps': lambda obj: json.dumps(obj, sort_keys=True, indent=4)}
SERIALIZER_DRIVERS['jsn'] = {'load': json.load, 'dumps': lambda obj: json.dumps(obj, sort_keys=True, indent=4)}
if has_yaml:
	SERIALIZER_DRIVERS['yaml'] = {'load': lambda file_obj: yaml.load(file_obj, Loader=Loader), 'dumps': lambda obj: yaml.dumps(obj, default_flow_style=False, Dumper=Dumper)}
	SERIALIZER_DRIVERS['yml'] = {'load': lambda file_obj: yaml.load(file_obj, Loader=Loader), 'dumps': lambda obj: yaml.dumps(obj, default_flow_style=False, Dumper=Dumper)}

class MemoryConfiguration(object):
	"""
	This class provides an interface for retrieving values from deeply nested
	objects supporting Python's __getitem__ interface.
	"""
	seperator = '.'
	def __init__(self, mem_object, prefix=''):
		"""
		:param smem_object: The memory object to parse.
		:param str prefix: String to be prefixed to all option names.
		:param str object_type: String to identify how to parse the mem_object.
		"""
		self.prefix = prefix
		if not hasattr(mem_object, '__getitem__'):
			raise ValueError('mem_object has no __getitem__ method')
		self._storage = mem_object

	def get(self, item_name):
		"""
		Retrieve the value of an option.

		:param str item_name: The name of the option to retrieve.
		:return: The value of *item_name* in the configuration.
		"""
		if self.prefix:
			item_name = self.prefix + self.seperator + item_name
		item_names = item_name.split(self.seperator)
		node = self._storage
		for item_name in item_names:
			node = node[item_name]
		return node

	def get_if_exists(self, item_name, default_value=None):
		"""
		Retrieve the value of an option if it exists, otherwise
		return *default_value* instead of raising an error:

		:param str item_name: The name of the option to retrieve.
		:param default_value: The value to return if *item_name* does not exist.
		:return: The value of *item_name* in the configuration.
		"""
		if self.has_option(item_name):
			return self.get(item_name)
		return default_value

	def get_storage(self):
		"""
		Get a copy of the internal configuration. Changes made to the returned
		copy will not affect this object.

		:return: A copy of the internal storage object.
		:rtype: dict
		"""
		return copy.deepcopy(self._storage)

	def has_option(self, option_name):
		"""
		Check that an option exists.

		:param str option_name: The name of the option to check.
		:return: True of the option exists in the configuration.
		:rtype: bool
		"""
		if self.prefix:
			option_name = self.prefix + self.seperator + option_name
		item_names = option_name.split(self.seperator)
		node = self._storage
		for item_name in item_names:
			if node is None:
				return False
			if not item_name in node:
				return False
			node = node[item_name]
		return True

	def has_section(self, section_name):
		"""
		Checks that an option exists and that it contains sub options.

		:param str section_name: The name of the section to check.
		:return: True if the section exists.
		:rtype: dict
		"""
		if not self.has_option(section_name):
			return False
		return isinstance(self.get(section_name), dict)

	def set(self, item_name, item_value):
		"""
		Sets the value of an option in the configuration.

		:param str item_name: The name of the option to set.
		:param item_value: The value of the option to set.
		"""
		if self.prefix:
			item_name = self.prefix + self.seperator + item_name
		item_names = item_name.split(self.seperator)
		item_last = item_names.pop()
		node = self._storage
		for item_name in item_names:
			if not item_name in node:
				node[item_name] = {}
			node = node[item_name]
		node[item_last] = item_value
		return

class Configuration(MemoryConfiguration):
	"""
	This class provides a generic object for parsing configuration files
	in multiple formats.
	"""
	def __init__(self, configuration_file, prefix=''):
		"""
		:param str configuration_file: The configuration file to parse.
		:param str prefix: String to be prefixed to all option names.
		"""
		self.configuration_file = configuration_file
		with open(self.configuration_file, 'r') as file_h:
			mem_object = self._serializer('load', file_h)
		super(Configuration, self).__init__(mem_object, prefix)

	@property
	def configuration_file_ext(self):
		"""
		The extension of the current configuration file.
		"""
		return os.path.splitext(self.configuration_file)[1][1:]

	def _serializer(self, operation, *args):
		if not self.configuration_file_ext in SERIALIZER_DRIVERS:
			raise ValueError('unknown file type \'' + self.configuration_file_ext + '\'')
		function = SERIALIZER_DRIVERS[self.configuration_file_ext][operation]
		return function(*args)

	def get_missing(self, verify_file):
		"""
		Use a verification configuration which has a list of required options
		and their respective types. This information is used to identify missing
		and incompatible options in the loaded configuration.

		:param str verify_file: The file to load for verification data.
		:return: A dictionary of missing and incompatible settings.
		:rtype: dict
		"""
		vconf = Configuration(verify_file)
		missing = {}
		for setting, setting_type in vconf.get('settings').items():
			if not self.has_option(setting):
				missing['missing'] = missing.get('settings', [])
				missing['missing'].append(setting)
			elif not type(self.get(setting)).__name__ == setting_type:
				missing['incompatible'] = missing.get('incompatible', [])
				missing['incompatible'].append((setting, setting_type))
		return missing

	def save(self):
		"""
		Save the current configuration to disk.
		"""
		with open(self.configuration_file, 'w') as file_h:
			file_h.write(self._serializer('dumps', self._storage))

def main():
	import argparse

	parser = argparse.ArgumentParser(description='Parse a configuration file', conflict_handler='resolve')
	parser.add_argument('config_file', action='store', help='configuration file to parse')
	parser.add_argument('option', action='store', help='option to retreive the value from')
	arguments = parser.parse_args()

	config = Configuration(arguments.config_file)
	if not config.has_option(arguments.option):
		return 1
	option_value = config.get(arguments.option)
	if isinstance(option_value, list):
		for value in option_value:
			print(value) # pylint: disable=C0325
		return 0
	print(option_value) # pylint: disable=C0325
	return 0

if __name__ == '__main__':
	sys.exit(main())
