# Copyright European Organization for Nuclear Research (CERN) since 2012
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import importlib
import os
from collections.abc import Callable
from configparser import NoOptionError, NoSectionError
from typing import Any, TypeVar

from rucio.common import config
from rucio.common.exception import InvalidAlgorithmName

PolicyPackageAlgorithmsT = TypeVar('PolicyPackageAlgorithmsT', bound='PolicyPackageAlgorithms')


class PolicyPackageAlgorithms:
    """
    Base class for Rucio Policy Package Algorithms

    ALGORITHMS is of type Dict[str, Dict[str. Callable[..., Any]]]
    where the key is the algorithm type and the value is a dictionary of algorithm names and their callables
    """
    _ALGORITHMS: dict[str, dict[str, Callable[..., Any]]] = {}
    _loaded_policy_modules = False

    def __init__(self) -> None:
        if not self._loaded_policy_modules:
            self._register_all_policy_package_algorithms()
            self._loaded_policy_modules = True

    @classmethod
    def _get_one_algorithm(cls: type[PolicyPackageAlgorithmsT], algorithm_type: str, name: str) -> Callable[..., Any]:
        """
        Get the algorithm from the dictionary of algorithms
        """
        return cls._ALGORITHMS[algorithm_type][name]

    @classmethod
    def _get_algorithms(cls: type[PolicyPackageAlgorithmsT], algorithm_type: str) -> dict[str, Callable[..., Any]]:
        """
        Get the dictionary of algorithms for a given type
        """
        return cls._ALGORITHMS[algorithm_type]

    @classmethod
    def _register(
            cls: type[PolicyPackageAlgorithmsT],
            algorithm_type: str, algorithm_dict: dict[str, Callable[..., Any]]) -> None:
        """
        Provided a dictionary of callable function,
        and the associated algorithm type,
        register it as one of the valid algorithms.
        """
        if algorithm_type in cls._ALGORITHMS:
            cls._ALGORITHMS[algorithm_type].update(algorithm_dict)
        else:
            cls._ALGORITHMS[algorithm_type] = algorithm_dict

    @classmethod
    def _supports(cls: type[PolicyPackageAlgorithmsT], algorithm_type: str, name: str) -> bool:
        """
        Check if a algorithm is supported by the plugin
        """
        return name in cls._ALGORITHMS.get(algorithm_type, {})

    @classmethod
    def _register_all_policy_package_algorithms(cls: type[PolicyPackageAlgorithmsT]) -> None:
        '''
        Loads all the algorithms of a given type from the policy package(s) and registers them
        :param algorithm_type: the type of algorithm to register (e.g. 'lfn2pfn')
        :param dictionary: the dictionary to register them in
        :param vo: the name of the relevant VO (None for single VO)
        '''
        try:
            multivo = config.config_get_bool('common', 'multi_vo')
        except (NoOptionError, NoSectionError):
            multivo = False
        if not multivo:
            # single policy package
            cls._try_importing_policy()
        else:
            # determine whether on client or server
            client = False
            if 'RUCIO_CLIENT_MODE' not in os.environ:
                if not config.config_has_section('database') and config.config_has_section('client'):
                    client = True
            else:
                if os.environ['RUCIO_CLIENT_MODE']:
                    client = True

            # on client, only register algorithms for selected VO
            if client:
                if 'RUCIO_VO' in os.environ:
                    vo = os.environ['RUCIO_VO']
                else:
                    try:
                        vo = str(config.config_get('client', 'vo'))
                    except (NoOptionError, NoSectionError):
                        vo = 'def'
                cls._try_importing_policy(vo)
            # on server, list all VOs and register their algorithms
            else:
                from rucio.core.vo import list_vos
                # policy package per VO
                vos = list_vos()
                for vo in vos:
                    cls._try_importing_policy(vo['vo'])

    @classmethod
    def _try_importing_policy(cls: type[PolicyPackageAlgorithmsT], vo: str = "") -> None:
        try:
            # import from utils here to avoid circular import
            from rucio.common.utils import check_policy_package_version

            env_name = 'RUCIO_POLICY_PACKAGE' + ('' if not vo else '_' + vo.upper())
            package = getattr(os.environ, env_name, "")
            if not package:
                package = str(config.config_get('policy', 'package' + ('' if not vo else '-' + vo)))

            check_policy_package_version(package)
            module = importlib.import_module(package)

            if hasattr(module, 'get_algorithms'):
                all_algorithms = module.get_algorithms()

                # for backward compatibility, rename 'surl' to 'non_deterministic_pfn' here
                if 'surl' in all_algorithms:
                    all_algorithms['non_deterministic_pfn'] = all_algorithms['surl']

                # check that the names are correctly prefixed for multi-VO
                if vo:
                    for _, algorithms in all_algorithms.items():
                        for k in algorithms.keys():
                            if not k.lower().startswith(vo.lower()):
                                raise InvalidAlgorithmName(k, vo)

                # Updates the dictionary with the algorithms from the policy package
                for algorithm_type, algorithm_dict in all_algorithms.items():
                    cls._register(algorithm_type, algorithm_dict)

        except (NoOptionError, NoSectionError, ImportError):
            pass