# Copyright 2023 VyOS maintainers and contributors <maintainers@vyos.io>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library 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
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with this library.  If not, see <http://www.gnu.org/licenses/>.

import os
import json
import typing
from inspect import stack
from graphlib import TopologicalSorter, CycleError

from vyos.utils.system import load_as_module
from vyos.configdict import dict_merge
from vyos.defaults import directories
from vyos.configsource import VyOSError
from vyos import ConfigError

# https://peps.python.org/pep-0484/#forward-references
# for type 'Config'
if typing.TYPE_CHECKING:
    from vyos.config import Config

dependency_dir = os.path.join(directories['data'],
                              'config-mode-dependencies')

dependent_func: dict[str, list[typing.Callable]] = {}

def canon_name(name: str) -> str:
    return os.path.splitext(name)[0].replace('-', '_')

def canon_name_of_path(path: str) -> str:
    script = os.path.basename(path)
    return canon_name(script)

def caller_name() -> str:
    return stack()[-1].filename

def read_dependency_dict(dependency_dir: str = dependency_dir) -> dict:
    res = {}
    for dep_file in os.listdir(dependency_dir):
        if not dep_file.endswith('.json'):
            continue
        path = os.path.join(dependency_dir, dep_file)
        with open(path) as f:
            d = json.load(f)
        if dep_file == 'vyos-1x.json':
            res = dict_merge(res, d)
        else:
            res = dict_merge(d, res)

    return res

def get_dependency_dict(config: 'Config') -> dict:
    if hasattr(config, 'cached_dependency_dict'):
        d = getattr(config, 'cached_dependency_dict')
    else:
        d = read_dependency_dict()
        setattr(config, 'cached_dependency_dict', d)
    return d

def run_config_mode_script(script: str, config: 'Config'):
    path = os.path.join(directories['conf_mode'], script)
    name = canon_name(script)
    mod = load_as_module(name, path)

    config.set_level([])
    try:
        c = mod.get_config(config)
        mod.verify(c)
        mod.generate(c)
        mod.apply(c)
    except (VyOSError, ConfigError) as e:
        raise ConfigError(repr(e))

def def_closure(target: str, config: 'Config',
                tagnode: typing.Optional[str] = None) -> typing.Callable:
    script = target + '.py'
    def func_impl():
        if tagnode:
            os.environ['VYOS_TAGNODE_VALUE'] = tagnode
        run_config_mode_script(script, config)
    return func_impl

def set_dependents(case: str, config: 'Config',
                   tagnode: typing.Optional[str] = None):
    d = get_dependency_dict(config)
    k = canon_name_of_path(caller_name())
    l = dependent_func.setdefault(k, [])
    for target in d[k][case]:
        func = def_closure(target, config, tagnode)
        l.append(func)

def call_dependents():
    k = canon_name_of_path(caller_name())
    l = dependent_func.get(k, [])
    while l:
        f = l.pop(0)
        f()

def graph_from_dependency_dict(d: dict) -> dict:
    g = {}
    for k in list(d):
        g[k] = set()
        # add the dependencies for every sub-case; should there be cases
        # that are mutally exclusive in the future, the graphs will be
        # distinguished
        for el in list(d[k]):
            g[k] |= set(d[k][el])

    return g

def is_acyclic(d: dict) -> bool:
    g = graph_from_dependency_dict(d)
    ts = TopologicalSorter(g)
    try:
        # get node iterator
        order = ts.static_order()
        # try iteration
        _ = [*order]
    except CycleError:
        return False

    return True

def check_dependency_graph(dependency_dir: str = dependency_dir,
                           supplement: str = None) -> bool:
    d = read_dependency_dict(dependency_dir=dependency_dir)
    if supplement is not None:
        with open(supplement) as f:
            d = dict_merge(json.load(f), d)

    return is_acyclic(d)