"""
linux.py - Linux config implementation.

Copyright (c) EDCD, All Rights Reserved
Licensed under the GNU General Public License.
See LICENSE file.
"""
import os
import pathlib
import sys
from configparser import ConfigParser
from config import AbstractConfig, appname, logger

assert sys.platform == 'linux'


class LinuxConfig(AbstractConfig):
    """Linux implementation of AbstractConfig."""

    SECTION = 'config'
    # TODO: I dislike this, would rather use a sane config file format. But here we are.
    __unescape_lut = {'\\': '\\', 'n': '\n', ';': ';', 'r': '\r', '#': '#'}
    __escape_lut = {'\\': '\\', '\n': 'n', ';': ';', '\r': 'r'}

    def __init__(self, filename: str | None = None) -> None:
        super().__init__()
        # http://standards.freedesktop.org/basedir-spec/latest/ar01s03.html
        xdg_data_home = pathlib.Path(os.getenv('XDG_DATA_HOME', default='~/.local/share')).expanduser()
        self.app_dir_path = xdg_data_home / appname
        self.app_dir_path.mkdir(exist_ok=True, parents=True)

        self.plugin_dir_path = self.app_dir_path / 'plugins'
        self.plugin_dir_path.mkdir(exist_ok=True)

        self.respath_path = pathlib.Path(__file__).parent.parent

        self.internal_plugin_dir_path = self.respath_path / 'plugins'
        self.default_journal_dir_path = None  # type: ignore
        self.identifier = f'uk.org.marginal.{appname.lower()}'  # TODO: Unused?

        config_home = pathlib.Path(os.getenv('XDG_CONFIG_HOME', default='~/.config')).expanduser()

        self.filename = config_home / appname / f'{appname}.ini'
        if filename is not None:
            self.filename = pathlib.Path(filename)

        self.filename.parent.mkdir(exist_ok=True, parents=True)

        self.config: ConfigParser | None = ConfigParser(comment_prefixes=('#',), interpolation=None)
        self.config.read(self.filename)  # read() ignores files that dont exist

        # Ensure that our section exists. This is here because configparser will happily create files for us, but it
        # does not magically create sections
        try:
            self.config[self.SECTION].get("this_does_not_exist", fallback=None)
        except KeyError:
            logger.info("Config section not found. Backing up existing file (if any) and readding a section header")
            if self.filename.exists():
                (self.filename.parent / f'{appname}.ini.backup').write_bytes(self.filename.read_bytes())

            self.config.add_section(self.SECTION)

        if (outdir := self.get_str('outdir')) is None or not pathlib.Path(outdir).is_dir():
            self.set('outdir', self.home)

    def __escape(self, s: str) -> str:
        """
        Escape a string using self.__escape_lut.

        This does NOT support multi-character escapes.

        :param s: str - String to be escaped.
        :return: str - The escaped string.
        """
        out = ""
        for c in s:
            if c not in self.__escape_lut:
                out += c
                continue

            out += '\\' + self.__escape_lut[c]

        return out

    def __unescape(self, s: str) -> str:
        """
        Unescape a string.

        :param s: str - The string to unescape.
        :return: str - The unescaped string.
        """
        out: list[str] = []
        i = 0
        while i < len(s):
            c = s[i]
            if c != '\\':
                out.append(c)
                i += 1
                continue

            # We have a backslash, check what its escaping
            if i == len(s)-1:
                raise ValueError('Escaped string has unescaped trailer')

            unescaped = self.__unescape_lut.get(s[i+1])
            if unescaped is None:
                raise ValueError(f'Unknown escape: \\ {s[i+1]}')

            out.append(unescaped)
            i += 2

        return "".join(out)

    def __raw_get(self, key: str) -> str | None:
        """
        Get a raw data value from the config file.

        :param key: str - The key data is being requested for.
        :return: str - The raw data, if found.
        """
        if self.config is None:
            raise ValueError('Attempt to use a closed config')

        return self.config[self.SECTION].get(key)

    def get_str(self, key: str, *, default: str | None = None) -> str:
        """
        Return the string referred to by the given key if it exists, or the default.

        Implements :meth:`AbstractConfig.get_str`.
        """
        data = self.__raw_get(key)
        if data is None:
            return default  # type: ignore # Yes it could be None, but we're _assuming_ that people gave us a default

        if '\n' in data:
            raise ValueError('asked for string, got list')

        return self.__unescape(data)

    def get_list(self, key: str, *, default: list | None = None) -> list:
        """
        Return the list referred to by the given key if it exists, or the default.

        Implements :meth:`AbstractConfig.get_list`.
        """
        data = self.__raw_get(key)

        if data is None:
            return default  # type: ignore # Yes it could be None, but we're _assuming_ that people gave us a default

        split = data.split('\n')
        if split[-1] != ';':
            raise ValueError('Encoded list does not have trailer sentinel')

        return list(map(self.__unescape, split[:-1]))

    def get_int(self, key: str, *, default: int = 0) -> int:
        """
        Return the int referred to by key if it exists in the config.

        Implements :meth:`AbstractConfig.get_int`.
        """
        data = self.__raw_get(key)

        if data is None:
            return default

        try:
            return int(data)

        except ValueError as e:
            raise ValueError(f'requested {key=} as int cannot be converted to int') from e

    def get_bool(self, key: str, *, default: bool | None = None) -> bool:
        """
        Return the bool referred to by the given key if it exists, or the default.

        Implements :meth:`AbstractConfig.get_bool`.
        """
        if self.config is None:
            raise ValueError('attempt to use a closed config')

        data = self.__raw_get(key)
        if data is None:
            return default  # type: ignore # Yes it could be None, but we're _assuming_ that people gave us a default

        return bool(int(data))

    def set(self, key: str, val: int | str | list[str]) -> None:
        """
        Set the given key's data to the given value.

        Implements :meth:`AbstractConfig.set`.
        """
        if self.config is None:
            raise ValueError('attempt to use a closed config')

        to_set: str | None = None
        if isinstance(val, bool):
            to_set = str(int(val))

        elif isinstance(val, str):
            to_set = self.__escape(val)

        elif isinstance(val, int):
            to_set = str(val)

        elif isinstance(val, list):
            to_set = '\n'.join([self.__escape(s) for s in val] + [';'])

        else:
            raise ValueError(f'Unexpected type for value {type(val)=}')

        self.config.set(self.SECTION, key, to_set)
        self.save()

    def delete(self, key: str, *, suppress=False) -> None:
        """
        Delete the given key from the config.

        Implements :meth:`AbstractConfig.delete`.
        """
        if self.config is None:
            raise ValueError('attempt to use a closed config')

        self.config.remove_option(self.SECTION, key)
        self.save()

    def save(self) -> None:
        """
        Save the current configuration.

        Implements :meth:`AbstractConfig.save`.
        """
        if self.config is None:
            raise ValueError('attempt to use a closed config')

        with open(self.filename, 'w', encoding='utf-8') as f:
            self.config.write(f)

    def close(self) -> None:
        """
        Close this config and release any associated resources.

        Implements :meth:`AbstractConfig.close`.
        """
        self.save()
        self.config = None