# ========================================================================== #
#                                                                            #
#    KVMD - The main PiKVM daemon.                                           #
#                                                                            #
#    Copyright (C) 2018-2022  Maxim Devaev <mdevaev@gmail.com>               #
#                                                                            #
#    This program is free software: you can redistribute it and/or modify    #
#    it under the terms of the GNU General Public License as published by    #
#    the Free Software Foundation, either version 3 of the License, or       #
#    (at your option) any later version.                                     #
#                                                                            #
#    This program is distributed in the hope that it will be useful,         #
#    but WITHOUT ANY WARRANTY; without even the implied warranty of          #
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the           #
#    GNU General Public License for more details.                            #
#                                                                            #
#    You should have received a copy of the GNU General Public License       #
#    along with this program.  If not, see <https://www.gnu.org/licenses/>.  #
#                                                                            #
# ========================================================================== #


import contextlib
import json

from typing import Tuple
from typing import List
from typing import Dict
from typing import Generator
from typing import Callable
from typing import Optional
from typing import Any


# =====
class ConfigError(ValueError):
    pass


# =====
def build_raw_from_options(options: List[str]) -> Dict[str, Any]:
    raw: Dict[str, Any] = {}
    for option in options:
        (key, value) = (option.split("=", 1) + [None])[:2]  # type: ignore
        if len(key.strip()) == 0:
            raise ConfigError(f"Empty option key (required 'key=value' instead of {option!r})")
        if value is None:
            raise ConfigError(f"No value for key {key!r}")

        section = raw
        subs = list(filter(None, map(str.strip, key.split("/"))))
        for sub in subs[:-1]:
            section.setdefault(sub, {})
            section = section[sub]
        section[subs[-1]] = _parse_value(value)
    return raw


def _parse_value(value: str) -> Any:
    value = value.strip()
    if (
        not value.isdigit()
        and value not in ["true", "false", "null"]
        and not value.startswith(("{", "[", "\""))
    ):
        value = f"\"{value}\""
    return json.loads(value)


# =====
class Section(dict):
    def __init__(self) -> None:
        dict.__init__(self)
        self.__meta: Dict[str, Dict[str, Any]] = {}

    def _unpack(self, ignore: Optional[List[str]]=None) -> Dict[str, Any]:
        if ignore is None:
            ignore = []
        unpacked: Dict[str, Any] = {}
        for (key, value) in self.items():
            if key not in ignore:
                if isinstance(value, Section):
                    unpacked[key] = value._unpack()
                else:  # Option
                    unpacked[self._get_unpack_as(key)] = value  # pylint: disable=protected-access
        return unpacked

    def _set_meta(self, key: str, default: Any, unpack_as: str, help: str) -> None:  # pylint: disable=redefined-builtin
        self.__meta[key] = {
            "default": default,
            "unpack_as": unpack_as,
            "help": help,
        }

    def _get_default(self, key: str) -> Any:
        return self.__meta[key]["default"]

    def _get_unpack_as(self, key: str) -> str:
        return (self.__meta[key]["unpack_as"] or key)

    def _get_help(self, key: str) -> str:
        return self.__meta[key]["help"]

    def __getattribute__(self, key: str) -> Any:
        if key in self:
            return self[key]
        else:  # For pickling
            return dict.__getattribute__(self, key)


class Stub:
    pass


class Option:
    __type = type

    def __init__(
        self,
        default: Any,
        type: Optional[Callable[[Any], Any]]=None,  # pylint: disable=redefined-builtin
        if_empty: Any=Stub,
        only_if: str="",
        unpack_as: str="",
        help: str="",  # pylint: disable=redefined-builtin
    ) -> None:

        self.default = default
        self.type: Callable[[Any], Any] = (type or (self.__type(default) if default is not None else str))  # type: ignore
        self.if_empty = if_empty
        self.only_if = only_if
        self.unpack_as = unpack_as
        self.help = help

    def __repr__(self) -> str:
        return (
            f"<Option(default={self.default}, type={self.type}, if_empty={self.if_empty},"
            f" only_if={self.only_if}, unpack_as={self.unpack_as})>"
        )


# =====
@contextlib.contextmanager
def manual_validated(value: Any, *path: str) -> Generator[None, None, None]:
    try:
        yield
    except (TypeError, ValueError) as err:
        raise ConfigError(f"Invalid value {value!r} for key {'/'.join(path)!r}: {err}")


def make_config(raw: Dict[str, Any], scheme: Dict[str, Any], _keys: Tuple[str, ...]=()) -> Section:
    if not isinstance(raw, dict):
        raise ConfigError(f"The node {('/'.join(_keys) or '/')!r} must be a dictionary")

    config = Section()

    def make_full_key(key: str) -> Tuple[str, ...]:
        return _keys + (key,)

    def make_full_name(key: str) -> str:
        return "/".join(make_full_key(key))

    def process_option(key: str, no_only_if: bool=False) -> Any:
        if key not in config:
            option: Option = scheme[key]
            only_if = option.only_if
            only_if_negative = option.only_if.startswith("!")
            if only_if_negative:
                only_if = only_if[1:]

            if only_if and no_only_if:  # pylint: disable=no-else-raise
                # Перекрестный only_if запрещен
                raise RuntimeError(f"Found only_if recursion on key {make_full_name(key)!r}")
            elif only_if and (
                (not only_if_negative and not process_option(only_if, no_only_if=True))
                or (only_if_negative and process_option(only_if, no_only_if=True))
            ):
                # Если есть условие и оно ложно - ставим дефолт и не валидируем
                value = option.default
            else:
                value = raw.get(key, option.default)
                if option.if_empty != Stub and not value:
                    value = option.if_empty
                else:
                    try:
                        value = option.type(value)
                    except (TypeError, ValueError) as err:
                        raise ConfigError(f"Invalid value {value!r} for key {make_full_name(key)!r}: {err}")

            config[key] = value
            config._set_meta(  # pylint: disable=protected-access
                key=key,
                default=option.default,
                unpack_as=option.unpack_as,
                help=option.help,
            )
        return config[key]

    for key in scheme:
        if isinstance(scheme[key], Option):
            process_option(key)
        elif isinstance(scheme[key], dict):
            config[key] = make_config(raw.get(key, {}), scheme[key], make_full_key(key))
        else:
            raise RuntimeError(f"Incorrect scheme definition for key {make_full_name(key)!r}:"
                               f" the value is {type(scheme[key])!r}, not dict() or Option()")
    return config