Mini Shell

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

# Copyright © Cloud Linux GmbH & Cloud Linux Software, Inc 2010-2021 All Rights Reserved
#
# Licensed under CLOUD LINUX LICENSE AGREEMENT
# http://cloudlinux.com/docs/LICENSE.TXT

"""
This module contains SSA specific config parser:
- has defaults
- adds default values for ones missing in config file
- allows duplicates, the latest value is loaded
- performs value normalization during loading items:
    - to int
    - to float
    - to bool
- 'correlation' is case-insensitive and allowed to be
    on, off, 1, 0, yes, no, true, false
- loads default configuration in case of missing config file
"""

import logging
import os
import tempfile
from configparser import ConfigParser, NoSectionError
from typing import Callable, List


from ..internal.constants import config_file

default_section = 'ssa_conf'
logger = logging.getLogger('ssa_configuration_parser')


class SSAConfigParser(ConfigParser):
    """
    SSA specific configparser implementation
    """

    def __init__(self):
        defaults = {
            'domains_number': 10,
            'urls_number': 5,
            'request_number': 10,
            'requests_duration': 3.0,
            'time': 1,
            'correlation': True,
            'correlation_coefficient': 0.8,
            'ignore_list': '',
            'summary_notification_enabled': True
        }
        self._comments = {
            'domains_number': 'Size of TOP list for slow domains',
            'urls_number': 'Size of TOP list for slow urls',
            'request_number': 'The threshold value of slow requests number in the period of time to mark URL as a slow one',
            'requests_duration': 'The threshold value of request duration in seconds',
            'time': 'Period of time in hours required to analyze these requests',
            'correlation': 'Flag to enable or disable correlation (On/Off)',
            'correlation_coefficient': 'The threshold value of correlation coefficient',
            'ignore_list': 'List of URLs or domains that should not be included in a daily report',
            'summary_notification_enabled': 'Flag to enable or disable sending daily reports by e-mail (On/Off)'
        }
        self.ssa_defaults = defaults.copy()
        super().__init__(defaults, strict=False)

    @property
    def int_options(self) -> tuple:
        return 'domains_number', 'urls_number', 'request_number', 'time'

    @property
    def float_options(self) -> tuple:
        return 'requests_duration', 'correlation_coefficient'

    @property
    def bool_options(self) -> tuple:
        return 'correlation', 'summary_notification_enabled'

    def empty_value_fallback(self, meth: Callable, section: str,
                             option: str) -> str:
        """
        If the value is missing in config file, e.g. time=
        set the default one
        """
        try:
            val = meth(section, option)
        except (ValueError, NoSectionError):
            val = meth(section, option, vars=self.defaults(), fallback=self.ssa_defaults[option])
        return val

    def items(self, section: str = default_section, raw: bool = False,
              vars: dict = None) -> List[tuple]:
        """Return a list of (name, value) tuples for each option in a section.
        Adds special conversions.
        """
        d = self._defaults.copy()
        try:
            d.update(self._sections[section])
        except KeyError:
            if section != self.default_section:
                logger.info('Malformed ssa.conf, section "%s" is missed. '
                            'Default will be applied ',
                            section)
            self.restore_default_conf()
        orig_keys = list(d.keys())

        def value_getter(option):
            if option in self.bool_options:
                return self.empty_value_fallback(self.getboolean, section,
                                                 option)
            elif option in self.int_options:
                return self.empty_value_fallback(self.getint, section, option)
            elif option in self.float_options:
                return self.empty_value_fallback(self.getfloat, section,
                                                 option)
            else:
                return d[option]

        return [(option, value_getter(option)) for option in orig_keys]

    def read_ssa_conf(self):
        """
        Try to read configuration from file,
        load defaults if file not present
        """
        try:
            with open(config_file):
                pass
            self.read(config_file)
        except FileNotFoundError:
            self.read_dict({default_section: self.defaults()})

    def write_ssa_conf(self) -> None:
        """
        Try to write current configuration to file,
        """
        temp_file = None
        try:
            temp_file = tempfile.NamedTemporaryFile(mode='w', dir=os.path.dirname(config_file), delete=False)
            # Write the configuration to the temporary file
            self.write(temp_file, space_around_delimiters=False)
            # If the writing process completes without any errors, rename the temporary file to the config file
            os.rename(temp_file.name, config_file)
        finally:
            if temp_file is not None:
                temp_file.close()
                if os.path.exists(temp_file.name):
                    os.remove(temp_file.name)

    def override(self, args: dict) -> None:
        """
        Load options from the dict into the main section of the config.
        """
        section = default_section if default_section in self.sections() else self.sections()[0]
        for option, value in args.items():
            self.set(section, option, str(value))

    def write(self, fp, space_around_delimiters=True):
        """
        Parent method is overrided in order to:
            - do not print default section
            - call its own write_section method instead of parent one.
        """
        if space_around_delimiters:
            d = ' {} '.format(self._delimiters[0])
        else:
            d = self._delimiters[0]
        for section in self._sections:
            self.write_section(fp, section,
                                self._sections[section].items(), d)

    def write_section(self, fp, section_name, section_items, delimiter):
        """
        The difference between this one and the parent _write_section method
        is in writing the comments to every option also
        """
        comment_prefix = self._comment_prefixes[0] if self._comment_prefixes else '#'
        fp.write('[{}]\n'.format(section_name))
        for key, value in section_items:
            value = self._interpolation.before_write(self, section_name, key,
                                                     value)
            if value is not None or not self._allow_no_value:
                value = delimiter + str(value).replace('\n', '\n\t')
            else:
                value = ''
            comment = self._comments.get(key, None)
            if comment is None:
                fp.write(f'{key}{value}\n\n')
            else:
                fp.write(f'{comment_prefix} {comment}\n{key}{value}\n\n')
        fp.write('\n')

    def restore_default_conf(self):
        """
        Clear all sections in config parser, try to copy settings values if they have it.
        Add new default section and pass all settings to it.
        """
        previous_settings = self.ssa_defaults
        for section in self.sections():
            for option in self.options(section):
                if option in previous_settings:
                    previous_settings[option] = self.get(section, option)
            self.remove_section(section)
        self.add_section(default_section)
        for option, value in previous_settings.items():
            self.set(default_section, option, str(value))