config_base.py

"""Load configuration settings for protonfixes"""

import re

from configparser import ConfigParser
from dataclasses import is_dataclass
from pathlib import Path

from typing import Any
from collections.abc import Callable

from .logger import log


class ConfigBase:
    """Base class for configuration objects.

    This reflects a given config file and populates the object with it's values.
    It also injects attributes from the sub classes, this isn't compatible with static type checking though.
    You can define the attributes accordingly to satisfy type checkers.
    """

    __CAMEL_CASE_PATTERN: re.Pattern = re.compile(
        '((?<=[a-z0-9])[A-Z]|(?!^)[A-Z](?=[a-z]))'
    )

    @classmethod
    def snake_case(cls, input: str) -> str:
        """Converts CamelCase to snake_case.

        Args:
            input (str): The string to convert.

        Returns:
            str: The converted string.

        """
        return cls.__CAMEL_CASE_PATTERN.sub(r'_\1', input).lower()

    @staticmethod
    def __log(message: str, level: str = 'INFO') -> None:
        log.log(f'[CONFIG]: {message}', level)

    def __init__(self, path: Path) -> None:
        """Initialize the instance from a given config file.

        Defaults will be used if the file doesn't exist.
        The file will also be created in this case.

        Args:
            path (Path): The reflected config file's path.

        Raises:
            IsADirectoryError: If the path exists, but isn't a file.

        """
        assert path
        if path.is_file():
            self.parse_config_file(path)
        elif not path.exists():
            self.init_sections()
            self.write_config_file(path)
        else:
            raise IsADirectoryError(
                f'Given path "{path.absolute()}" exists, but is not a file.'
            )

    def init_sections(self, force: bool = False) -> None:
        """Find sub-classes and initialize them as attributes.

        Sub-classes are initialized and injected as attributes.
        Example: `MainSection` will be injected as `main` to the config (this) object.

        Args:
            force (bool, optional): Force initialization? This results in a reset. Defaults to False.

        """
        for member_name, member in self.__class__.__dict__.items():
            # Find non private section definitions
            if not member_name.endswith('Section') or member_name.startswith('_'):
                continue
            if not is_dataclass(member):
                continue

            # Convert section definition class name to variable name (MyCfgSection -> my_cfg)
            section_name = member_name.removesuffix('Section')
            section_name = self.snake_case(section_name)

            # Do not override existing members by default
            if hasattr(self, section_name) and not force:
                continue

            # Initialize section class as a member
            setattr(self, section_name, member())  # pyright: ignore [reportCallIssue]

    def parse_config_file(self, file: Path) -> bool:
        """Parse a config file.

        This resets the data in the sections, regardless if the file exists or is loaded.

        Args:
            file (Path): The reflected config file's path.

        Returns:
            bool: True, if the config file was successfully loaded.

        """
        # Initialize / reset sections to defaults
        self.init_sections(True)

        # Only precede if the config file exists
        if not file.is_file():
            return False

        try:
            parser = ConfigParser()
            parser.read(file)

            # Iterate over local config section objects
            for section_name, section in self.__dict__.items():
                if not parser.has_section(section_name):
                    continue

                parser_items = parser[section_name]

                # FIXME: match is not supported in Python 3.9
                def _get_parse_function(type_name: str) -> Callable[[str], Any]:
                    # Mapping of type_name to according value get function
                    value = {
                        'int': parser_items.getint,
                        'float': parser_items.getfloat,
                        'bool': parser_items.getboolean,
                        'Path': lambda option: Path(parser_items.get(option, '')),
                        'PosixPath': lambda option: Path(parser_items.get(option, '')),
                        'str': parser_items.get,
                    }.get(type_name, None)
                    if not value:
                        value = parser_items.get
                        self.__log(
                            f'Unknown type "{type_name}", falling back to "str".',
                            'WARN',
                        )
                    return value

                # Iterate over the option objects in this section
                for option_name, option_item in section.__dict__.items():
                    # Get values from config and set it on object
                    type_name = type(option_item).__name__
                    func = _get_parse_function(type_name)
                    value = func(option_name)
                    setattr(section, option_name, value)
        except Exception as ex:
            self.__log(
                f'Failed to parse config file "{file}". Exception: "{ex}"', 'CRIT'
            )
            return False
        return True

    def write_config_file(self, file: Path) -> bool:
        """Write the current config to a file.

        Args:
            file (Path): The file path to write to.

        Returns:
            bool: True, if the file was successfully written.

        """
        # Only precede if the parent directory exists
        if not file.parent.is_dir():
            self.__log(
                f'Parent directory "{file.parent}" does not exist. Abort.', 'WARN'
            )
            return False

        # Create and populate ConfigParser
        try:
            parser = ConfigParser()
            # Iterate over local config section objects
            for section_name, section_item in self.__dict__.items():
                if not parser.has_section(section_name):
                    parser.add_section(section_name)

                for option_name, option_item in section_item.__dict__.items():
                    parser.set(section_name, option_name, str(option_item))

            # Write config file
            with file.open(mode='w') as stream:
                parser.write(stream)
        except Exception as ex:
            self.__log(
                f'Failed to create config file "{file}". Exception: "{ex}"', 'CRIT'
            )
            return False
        return True