# -*- coding: utf-8 -*-

""" Configuration & options parser """

import argparse
from configparser import ConfigParser
from getpass import getpass
from logging.config import fileConfig
import logging
import os
import re
import stat
import sys
import textwrap
import traceback

import argcomplete
import keyring
from systemd.journal import JournalHandler


log = logging.getLogger(__name__)


# Constants
DEFAULT_ENCODING = 'utf-8'
DEFAULT_CONFIG_DIRPATH = os.path.expanduser('./')


class BaseOption:  # pylint: disable=too-many-instance-attributes
    """ Base configuration option class """

    def __init__(self, config, section, name, default=None, comment=None,
                 arg=None, short_arg=None, arg_help=None, no_arg=False):
        self.config = config
        self.section = section
        self.name = name
        self.default = default
        self.comment = comment
        self.no_arg = no_arg
        self.arg = arg
        self.short_arg = short_arg
        self.arg_help = arg_help if arg_help else comment

    @property
    def _isset_in_options(self):
        """ Check if option is defined in registered arguments parser options """
        return (
            self.config.options
            and not self.no_arg
            and self._from_options != self.default
        )

    @property
    def _from_options(self):
        """ Get option from arguments parser options """
        value = (
            getattr(self.config.options, self.parser_dest)
            if self.config.options and not self.no_arg else None
        )
        log.debug(
            '_from_options(%s, %s) = %s',
            self.section.name, self.name, value
        )
        return value

    @property
    def _isset_in_config_file(self):
        """ Check if option is defined in the loaded configuration file """
        return (
            self.config.config_parser
            and self.config.config_parser.has_option(self.section.name, self.name)
        )

    @property
    def _from_config(self):
        """ Get option value from ConfigParser """
        return self.config.config_parser.get(self.section.name, self.name)

    def isset(self):
        """ Check if option is defined in the loaded configuration file """
        return self._isset_in_config_file or self._isset_in_options

    def get(self):
        """ Get option value from options, config or default """
        if self._isset_in_options:
            return self._from_options
        if self._isset_in_config_file:
            return self._from_config
        return self.default

    def set(self, value):
        """ Set option value to config file """
        assert self.config.config_parser or (self.config.options and not self.no_arg), (
            "Can't set option value: configuration file not configured, not options (or no argument)")
        if value == '':
            value = None

        if self.config.config_parser:
            if value == self.default or value is None:
                # Remove option from config (is section exists)
                if self.config.config_parser.has_section(self.section.name):
                    self.config.config_parser.remove_option(
                        self.section.name, self.name)
            else:
                # Store option to config
                if not self.config.config_parser.has_section(self.section.name):
                    self.config.config_parser.add_section(self.section.name)

                self.config.config_parser.set(
                    self.section.name, self.name, self.to_config(value)
                )

        if self.config.options and not self.no_arg:
            setattr(self.config.options, self.parser_dest, value)

    @property
    def parser_action(self):
        """ Get action as accept by argparse.ArgumentParser """
        return 'store'

    @property
    def parser_type(self):
        """ Get type as handle by argparse.ArgumentParser """
        return str

    @property
    def parser_dest(self):
        """ Get option name in arguments parser options """
        return '{0}_{1}'.format(self.section.name, self.name)

    @property
    def parser_help(self):
        """ Get option help message in arguments parser options """
        if self.arg_help and self.default is not None:
            return '{0} (Default: {1})'.format(self.arg_help, self.default)
        if self.arg_help:
            return self.arg_help
        return None

    @property
    def parser_argument_name(self):
        """ Get option argument name in parser options """
        return (
            self.arg if self.arg else
            '--{0}-{1}'.format(
                self.section.name, self.name
            ).lower().replace('_', '-')
        )

    def add_option_to_parser(self, section_opts):
        """ Add option to arguments parser """
        if self.no_arg:
            return
        args = [self.parser_argument_name]
        if self.short_arg:
            args.append(self.short_arg)
        kwargs = dict(
            action=self.parser_action,
            dest=self.parser_dest,
            help=self.parser_help,
            default=self.default,
        )
        if self.parser_type:  # pylint: disable=using-constant-test
            kwargs['type'] = self.parser_type

        log.debug(
            'add_option_to_parser(%s, %s): argument name(s)=%s / kwargs=%s',
            self.section.name, self.name, ', '.join(args), kwargs
        )
        section_opts.add_argument(*args, **kwargs)

    def to_config(self, value=None):
        """ Format value as stored in configuration file """
        value = value if value is not None else self.get()
        return '' if value is None else str(value)

    def export_to_config(self):
        """ Export option to configuration file """
        lines = []
        if self.comment:
            lines.append('# ' + self.comment)
        value = self.to_config()
        default_value = (
            '' if self.default is None else
            self.to_config(self.default)
        )
        log.debug(
            'export_to_config(%s, %s): value=%s / default=%s',
            self.section.name, self.name, value, default_value)
        if default_value:
            lines.append(
                '# Default: %s' % default_value
            )
        if value and value != default_value:
            lines.append(
                '%s = %s' %
                (self.name, value)
            )
        else:
            lines.append('# %s =' % self.name)
        lines.append('')
        return '\n'.join(lines)

    def _ask_value(self, prompt=None, **kwargs):
        """ Ask to user to enter value of this option and return it """
        if self.comment:
            print('# ' + self.comment)
        default_value = kwargs.get('default_value', self.get())
        if not prompt:
            prompt = "%s: " % self.name
            if default_value is not None:
                prompt += "[%s] " % self.to_config(default_value)
        value = input(prompt)
        return default_value if value == '' else value

    def ask_value(self, set_it=True):
        """
        Ask to user to enter value of this option and set or
        return it regarding set parameter
        """
        value = self._ask_value()
        if set_it:
            return self.set(value)
        return value


class StringOption(BaseOption):
    """ String configuration option class """


class BooleanOption(BaseOption):
    """ Boolean configuration option class """

    @property
    def _from_config(self):
        """ Get option value from ConfigParser """
        return self.config.config_parser.getboolean(self.section.name, self.name)

    def to_config(self, value=None):
        """ Format value as stored in configuration file """
        return super().to_config(value).lower()

    @property
    def parser_action(self):
        return "store_" + str(bool(not self.default)).lower()

    @property
    def parser_type(self):
        return None

    @property
    def parser_argument_name(self):
        """ Get option argument name in parser options """
        return (
            self.arg if self.arg else
            '--{0}-{1}-{2}'.format(
                self.section.name,
                'enable' if not self.default else 'disable',
                self.name
            ).lower().replace('_', '-')
        )

    def _ask_value(self, prompt=None, **kwargs):
        """ Ask to user to enter value of this option and return it """
        default_value = self.get()
        prompt = "%s: " % self.name
        if default_value:
            prompt += '[Y/n] '
        else:
            prompt += '[y/N] '
        while True:
            value = super()._ask_value(prompt, **kwargs)
            if value in ['', None, default_value]:
                return default_value
            if value.lower() == 'y':
                return True
            if value.lower() == 'n':
                return False

            print('Invalid answer. Possible values: Y or N (case insensitive)')


class FloatOption(BaseOption):
    """ Float configuration option class """

    @property
    def _from_config(self):
        """ Get option value from ConfigParser """
        return self.config.config_parser.getfloat(self.section.name, self.name)

    @property
    def parser_type(self):
        return float

    def _ask_value(self, prompt=None, **kwargs):
        """ Ask to user to enter value of this option and return it """
        default_value = self.get()
        while True:
            value = super()._ask_value(prompt, **kwargs)
            if value in ['', None, default_value]:
                return default_value
            try:
                return float(value)
            except ValueError:
                print('Invalid answer. Must a numeric value, for instance "12" or "12.5"')


class IntegerOption(BaseOption):
    """ Integer configuration option class """

    @property
    def _from_config(self):
        """ Get option value from ConfigParser """
        return self.config.config_parser.getint(self.section.name, self.name)

    def to_config(self, value=None):
        """ Format value as stored in configuration file """
        value = value if value is not None else self.get()
        return str(int(value)) if value is not None else ''

    @property
    def parser_type(self):
        return int

    def _ask_value(self, prompt=None, **kwargs):
        """ Ask to user to enter value of this option and return it """
        default_value = kwargs.pop('default_value', self.get())
        while True:
            value = super()._ask_value(prompt, default_value=default_value, **kwargs)
            if value in ['', None, default_value]:
                return default_value
            try:
                return int(value)
            except ValueError:
                print('Invalid answer. Must a integer value')


class PasswordOption(StringOption):
    """ Password configuration option class """

    def __init__(self, *arg, username_option=None, keyring_value=None, **kwargs):
        super().__init__(*arg, **kwargs)
        self.username_option = username_option
        self.keyring_value = keyring_value if keyring_value is not None else 'keyring'

    @property
    def _keyring_service_name(self):
        """ Return keyring service name """
        return '.'.join([
            self.config.shortname,
            self.section.name, self.name
        ])

    @property
    def _keyring_username(self):
        """ Return keyring username """
        return self.section.get(self.username_option) if self.username_option else self.name

    def get(self):
        """ Get option value """
        value = super().get()

        if value != self.keyring_value:
            return value

        service_name = self._keyring_service_name
        username = self._keyring_username
        log.debug(
            'Retreive password %s for username=%s from keyring',
            service_name, username
        )
        value = keyring.get_password(service_name, username)

        if value is None:
            value = getpass(
                'Please enter %s%s: ' % (
                    self.comment if self.comment else
                    '%s %s' % (self.section.name, self.name),
                    (' for %s' % username)
                    if username != self.name else ''
                )
            )
            keyring.set_password(service_name, username, value)
        return value

    def to_config(self, value=None):
        """ Format value as stored in configuration file """
        if super().get() == self.keyring_value:
            return self.keyring_value
        return super().to_config(value)

    def set(self, value, use_keyring=None):  # pylint: disable=arguments-differ
        """ Set option value to config file """
        if (use_keyring is None and super().get() == self.keyring_value) or use_keyring:
            keyring.set_password(
                self._keyring_service_name, self._keyring_username,
                value)
            value = self.keyring_value
        super().set(value)

    def _ask_value(self, prompt=None, **kwargs):
        """ Ask to user to enter value of this option and return it """
        if self.comment:
            print('# ' + self.comment)
        default_value = kwargs.pop('default_value', self.get())
        if not prompt:
            prompt = '%s: ' % self.name
            if default_value is not None:
                # Hide value only if it differed from default value
                if default_value == self.default:
                    prompt += '[%s] ' % default_value
                else:
                    prompt += '[secret defined, leave to empty to keep it as unchange] '
        value = getpass(prompt)
        return default_value if value == '' else value

    def ask_value(self, set_it=True):
        """
        Ask to user to enter value of this option and set or
        return it regarding set parameter
        """
        value = self._ask_value()
        if set_it:
            use_keyring = None
            default_use_keyring = (super().get() == self.keyring_value)
            while use_keyring is None:
                prompt = (
                    'Do you want to use XDG keyring ? [%s] ' %
                    ('Y/n' if default_use_keyring else 'y/N')
                )
                result = input(prompt).lower()
                if result == '':
                    use_keyring = default_use_keyring
                elif result == 'y':
                    use_keyring = True
                elif result == 'n':
                    use_keyring = False
                else:
                    print('Invalid answer. Possible values: Y or N (case insensitive)')
            return self.set(value, use_keyring=use_keyring)
        return value


class ConfigSection:
    """ Configuration section class """

    def __init__(self, config, name, comment=None, order=None):
        self.config = config
        self.name = name
        self.options = dict()
        self.comment = comment
        self.order = order if isinstance(order, int) else 10

    def add_option(self, _type, name, **kwargs):
        """
        Add option

        :param _type: Option type, derivated from BaseOption
        :param name: Option name
        :param **kwargs: Dict of raw option for type class
        """
        assert not self.defined(name), "Duplicated option %s" % name
        self.options[name] = _type(self.config, self, name, **kwargs)
        return self.options[name]

    def defined(self, option):
        """ Check if option is defined """
        return option in self.options

    def isset(self, option):
        """ Check if option is set """
        return self.defined(option) and self.options[option].isset()

    def get(self, option):
        """ Get option value """
        assert self.defined(option), "Option %s unknown" % option
        return self.options[option].get()

    def set(self, option, value):
        """ Set option value """
        assert self.defined(option), "Option %s unknown" % option
        return self.options[option].set(value)

    def add_options_to_parser(self, parser):
        """ Add section to argparse.ArgumentParser """
        assert isinstance(parser, argparse.ArgumentParser)
        section_opts = parser.add_argument_group(
            self.comment if self.comment
            else self.name.capitalize()
        )

        for option in self.options:
            self.options[option].add_option_to_parser(section_opts)

    def export_to_config(self):
        """ Export section and their options to configuration file """
        lines = []
        if self.comment:
            lines.append('# %s' % self.comment)
        lines.append('[%s]' % self.name)
        for option in self.options:
            lines.append(self.options[option].export_to_config())
        return '\n'.join(lines)

    def ask_values(self, set_it=True):
        """
        Ask user to enter value for each configuration option of the section

        :param set_it: If True (default), option value will be updated with user input

        :return: If set_it is True, return True if valid value for each configuration
        option have been retrieved and set. If False, return a dict of configuration
        options and their value.
        :rtype: bool of dict
        """
        if self.comment:
            print('# %s' % self.comment)
        print('[%s]\n' % self.name)
        result = dict()
        error = False
        for name, option in self.options.items():
            option_result = option.ask_value(set_it=set_it)
            if set_it:
                result[name] = option_result
            elif not option_result:
                error = True
            print()
        print()
        if set_it:
            return not error
        return result


class RawWrappedTextHelpFormatter(argparse.RawDescriptionHelpFormatter):
    """
    Custom TextHelpFormatter for argparse.ArgumentParser that allowing line to keep line return
    """

    def _split_lines(self, text, width):
        result = []
        for line in textwrap.dedent(text).splitlines():
            # Keep empty line
            if line == "":
                result.append(line)
                continue
            # Split ident prefix and line text
            m = re.match('^( *)(.*)$', line)
            ident = m.group(1)
            line_text = m.group(2)
            # Wrap each lines and add in result with ident prefix
            for l in textwrap.wrap(line_text, width - len(ident)):
                result.append(ident + l)
        return result


class Config:  # pylint: disable=too-many-instance-attributes
    """ Configuration helper """

    def __init__(self, appname, shortname=None, version=None, encoding=None,
                 config_file_env_variable=None):
        self.appname = appname
        self.shortname = shortname
        self.version = version if version else '0.0'
        self.encoding = encoding if encoding else 'utf-8'
        self.config_parser = None
        self.options_parser = None
        self.options = None
        self.sections = {}
        self._loaded_callbacks = []
        self._loaded_callbacks_executed = []
        self._filepath = None
        self.config_file_env_variable = config_file_env_variable

    def add_section(self, name, loaded_callback=None, **kwargs):
        """
        Add section

        : param name: The section name
        : param loaded_callback: An optional callback method that will be executed after configuration is loaded
                                The specified callback method will receive Config object as parameter.
        : param ** kwargs: Raw parameters dict pass to ConfigSection __init__() method
        """
        assert name not in self.sections, "Duplicated section %s" % name

        self.sections[name] = ConfigSection(self, name, **kwargs)
        if loaded_callback:
            self._loaded_callbacks.append(loaded_callback)
            # If configuration is already loaded, execute callback immediatly
            if self.config_parser or self.options:
                self._loaded()
        return self.sections[name]

    def defined(self, section, option):
        """ Check option is defined in specified section """
        return section in self.sections and self.sections[section].defined(option)

    def isset(self, section, option):
        """ Check option is set in specified section """
        return section in self.sections and self.sections[section].isset(option)

    def get(self, section, option):
        """ Get option value """
        assert self.config_parser or self.options, 'Unconfigured options parser'
        assert self.defined(
            section, option), 'Unknown option %s.%s' % (section, option)
        value = self.sections[section].get(option)
        log.debug('get(%s, %s): %s (%s)', section, option, value, type(value))
        return value

    def set(self, section, option, value):
        """ Set option value """
        assert self.config_parser, 'Unconfigured options parser'
        assert self.defined(
            section, option), 'Unknown option %s.%s' % (section, option)
        self.sections[section].set(option, value)

    def load_file(self, filepath, execute_callback=True):
        """ Read configuration file """

        self.config_parser = ConfigParser()
        self._filepath = filepath

        # Checking access of configuration file
        if not os.path.isfile(filepath):
            return True

        if not os.access(filepath, os.R_OK):
            return False

        try:
            self.config_parser.read(filepath, encoding=self.encoding)
        except Exception:  # pylint: disable=broad-except
            self.config_parser = None
            log.exception('Failed to read configuration file %s', filepath)
            return False

        # Logging initialization
        if self.config_parser.has_section('loggers'):
            fileConfig(filepath)
        else:
            # Otherwise, use systemd journal handler
            handler = JournalHandler(SYSLOG_IDENTIFIER=self.shortname)
            handler.setFormatter(
                logging.Formatter(
                    '%(levelname)s | %(name)s | %(message)s'
                )
            )
            logging.getLogger().addHandler(handler)

        self._filepath = filepath

        if execute_callback:
            self._loaded()

        return True

    def _loaded(self):
        """ Execute loaded callbacks """
        error = False
        for callback in self._loaded_callbacks:
            if callback in self._loaded_callbacks_executed:
                continue
            if not callback(self):
                error = True
            self._loaded_callbacks_executed.append(callback)
        return not error

    def save(self, filepath=None):
        """ Save configuration file """
        filepath = filepath if filepath else self._filepath
        assert filepath, 'Configuration filepath is not set or provided'

        # Checking access of target directory
        dirpath = os.path.dirname(filepath)
        if not os.path.isdir(dirpath) or not os.access(dirpath, os.R_OK | os.W_OK | os.X_OK):
            log.error(
                'Configuration directory "%s" does not exist (or not writable)', dirpath)
            return False

        if os.path.isfile(filepath) and not os.access(filepath, os.W_OK):
            log.error('Configuration file "%s" is not writable', filepath)
            return False

        lines = ['#\n# %s configuration\n#\n' % self.appname]

        for section_name in self._ordered_section_names:
            lines.append('')
            lines.append(self.sections[section_name].export_to_config())

        try:
            with open(filepath, 'wb') as fd:
                fd.write(
                    '\n'.join(lines).encode(self.encoding)
                )

            # Privacy!
            os.chmod(filepath, stat.S_IRUSR | stat.S_IWUSR)
        except Exception:  # pylint: disable=broad-except
            log.exception(
                'Failed to write generated configuration file %s', filepath)
            return False
        return True

    @property
    def _ordered_section_names(self):
        """ Get ordered list of section names """
        return sorted(self.sections.keys(), key=lambda section: self.sections[section].order)

    def get_arguments_parser(self, **kwargs):
        """ Get arguments parser """
        if self.options_parser:
            return self.options_parser

        self.options_parser = argparse.ArgumentParser(
            description=kwargs.pop('description', self.appname),
            formatter_class=RawWrappedTextHelpFormatter,
            **kwargs)

        config_file_help = 'Configuration file to use (default: %s)' % self.config_filepath
        if self.config_file_env_variable:
            config_file_help += '\n\nYou also could set %s environment variable to specify your configuration file path.' % self.config_file_env_variable
        self.options_parser.add_argument(
            '-c',
            '--config',
            default=self.config_filepath,
            help=config_file_help
        )

        self.options_parser.add_argument(
            '--save',
            action='store_true',
            dest='save',
            help='Save current configuration to file',
        )

        self.options_parser.add_argument(
            '-d',
            '--debug',
            action='store_true',
            help='Show debug messages'
        )

        self.options_parser.add_argument(
            '-v',
            '--verbose',
            action='store_true',
            help='Show verbose messages'
        )

        self.options_parser.add_argument(
            '-C',
            '--console',
            action='store_true',
            help='Log on console'
        )

        self.add_options_to_parser(self.options_parser)

        return self.options_parser

    def parse_arguments_options(self, argv=None, parser=None, create=True, ask_values=True,
                                exit_after_created=True, execute_callback=True):
        """
        Parse arguments options

        :param argv: Optional arguments list to parse (default: sys.argv[1:])
        :param parser: Optional argparse.ArgumentParser use
                       (default: generated by self.get_arguments_parser())
        :param create: If True, configuration file will be created if it does not exits
                       (default: True)
        :param ask_values: If True, ask user to enter valor of each configuration options
                           (default: True)
        :param exit_after_created: If True, script will end after configuration file
                                   creation (default: True)
        :param execute_callback: Sections's loaded callbacks will be executed only if True
                                 (default: True)
        """
        parser = parser if parser else self.get_arguments_parser()
        argcomplete.autocomplete(parser)
        options = parser.parse_args(argv if argv is not None else sys.argv[1:])
        self.load_options(options, execute_callback=False)

        if options.config:
            options.config = os.path.abspath(options.config)

            already_saved = False
            if not os.path.isfile(options.config) and (create or options.save):
                log.warning(
                    "Configuration file is missing, generate it (%s)",
                    options.config
                )
                if ask_values:
                    self.ask_values(set_it=True)
                self.save(options.config)
                if exit_after_created:
                    sys.exit(0)
                already_saved = True

            # Load configuration file
            if os.path.isfile(options.config) and not self.load_file(options.config, execute_callback=False):
                parser.error(
                    'Failed to load configuration from file %s' % options.config
                )

            if options.save and not already_saved:
                self.save()
                sys.exit(0)

        if options.debug:
            logging.getLogger().setLevel(logging.DEBUG)
        elif options.verbose:
            logging.getLogger().setLevel(logging.INFO)

        if options.console:
            console_handler = logging.StreamHandler(sys.stdout)
            logging.getLogger().addHandler(console_handler)

        if execute_callback:
            self._loaded()

        return options

    def load_options(self, options, execute_callback=True):
        """ Register arguments parser options """
        assert isinstance(options, argparse.Namespace)
        self.options = options
        log.debug('Argument options: %s', options)
        if execute_callback:
            self._loaded()

    def add_options_to_parser(self, parser):
        """ Add sections and their options to parser """
        for section in self._ordered_section_names:
            self.sections[section].add_options_to_parser(parser)

    def ask_values(self, set_it=True, execute_callback=False):
        """
        Ask user to enter value for each configuration option

        :param set_it: If True (default), option value will be updated with user input
        :param execute_callback: Sections's loaded callbacks will be finally executed
                                 (only if set_it is True, default: False)

        :return: If set_it is True, return True if valid value for each configuration
        option have been retrieved and set. If False, return a dict of configuration
        section and their options value.
        :rtype: bool of dict
        """
        # On set it mode, ensure configuration file parser is initialized
        if set_it and not self.config_parser:
            self.config_parser = ConfigParser()
        result = dict()
        error = False
        for name, section in self.sections.items():
            section_result = section.ask_values(set_it=set_it)
            if not set_it:
                result[name] = section_result
            elif not section_result:
                error = True
        if set_it:
            if error:
                return False
            if execute_callback:
                self._loaded()
            return True
        return result

    def configure(self, argv=None, description=False):
        """
        Entry point of a script you could use to created your configuration file

        Note: make sure to load to define all your configuration section and options
        before running it.
        """
        parser = self.get_arguments_parser(
            description=description if description else "Generate configuration file"
        )

        parser.add_argument(
            '-i', '--interactive',
            action='store_true', dest='interactive',
            help="Enable configuration interactive mode"
        )

        parser.add_argument(
            '-O', '--overwrite',
            action='store_true', dest='overwrite',
            help="Overwrite configuration file if exists"
        )

        parser.add_argument(
            '-V', '--validate',
            action='store_true', dest='validate',
            help=(
                "Validate configuration: initialize application to test if provided parameters works.\n\n"
                "Note: Validation will occured after configuration file creation or update. On error, "
                "re-run with -O/--overwrite parameter to fix it."
            )
        )

        options = self.parse_arguments_options(
            argv, create=False, execute_callback=False)

        if os.path.exists(options.config) and not options.overwrite:
            print('Configuration file %s already exists' % options.config)
            sys.exit(1)

        if options.interactive:
            self.ask_values(set_it=True)

        if self.save(options.config):
            print('Configuration file %s created.' % options.config)
            if options.validate:
                print('Validate your configuration...')
                try:
                    if self._loaded():
                        print('Your configuration seem valid.')
                    else:
                        print('Error(s) occurred validating your configuration. See logs for details.')
                        sys.exit(1)
                except Exception:
                    print(
                        'Exception occurred validating your configuration: %s\n\nSee logs for details.' %
                        traceback.format_exc())
                    sys.exit(2)
        else:
            print('Error occured creating configuration file %s' %
                  options.config)
            sys.exit(1)

        sys.exit(0)

    @property
    def config_dir(self):
        """ Retrieve configuration directory path """
        return os.path.dirname(self._filepath) if self._filepath else DEFAULT_CONFIG_DIRPATH

    @property
    def config_filepath(self):
        """ Retrieve configuration file path """
        if self._filepath:
            return self._filepath
        if self.config_file_env_variable and os.environ.get(self.config_file_env_variable):
            return os.environ.get(self.config_file_env_variable)
        return os.path.join(
            self.config_dir,
            ("%s.ini" % self.shortname) if self.shortname
            else "config.ini"
        )


class ConfigurableObject:
    """
    Base class of configurable object

    This class provide a way to configure an object using :
      - mylib.config.Config object
      - argparse.Namespace object
      - kwargs passed to __init__ method
    """

    # Configuration object name (used for default options prefix and config section)
    # Note: required if options_prefix or/and config_section parameters not provided
    # to __init__ method.
    _config_name = None

    # Configuration comment (used for config section)
    _config_comment = None

    # Default options value
    # Important: all supported options MUST HAVE a default value defined
    _defaults = {}

    # Store options passed throuht __init__ method
    _kwargs = {}
    _options = {}
    _options_prefix = None
    _config = None
    _config_section = None

    def __init__(self, options=None, options_prefix=None, config=None, config_section=None,
                 **kwargs):

        for key, value in kwargs.items():
            assert key in self._defaults, "Unknown %s option" % key
            self._kwargs[key] = value

        if options:
            self._options = options
            if options_prefix is not None:
                self._options_prefix = options_prefix
            elif self._config_name:
                self._options_prefix = self._config_name + '_'
            else:
                raise Exception('No configuration name defined for %s' % __name__)

        if config:
            self._config = config
            if config_section:
                self._config_section = config_section
            elif self._config_name:
                self._config_section = self._config_name
            else:
                raise Exception('No configuration name defined for %s' % __name__)

    def _get_option(self, option, default=None, required=False):
        """ Retreive option value """
        if self._kwargs and option in self._kwargs:
            return self._kwargs[option]

        if self._options and hasattr(self._options, self._options_prefix + option):
            return getattr(self._options, self._options_prefix + option)

        if self._config and self._config.defined(self._config_section, option):
            return self._config.get(self._config_section, option)

        assert not required, "Options %s not defined" % option

        return default if default is not None else self._defaults.get(option)

    def configure(self, comment=None, ** kwargs):
        """ Configure options on registered mylib.Config object """
        assert self._config, "mylib.Config object not registered. Must be passed to __init__ as config keyword argument."

        return self._config.add_section(
            self._config_section,
            comment=comment if comment else self._config_comment,
            loaded_callback=self.initialize, **kwargs)

    def initialize(self, loaded_config=None):
        """ Configuration initialized hook """
        if loaded_config:
            self.config = loaded_config  # pylint: disable=attribute-defined-outside-init