# (c) Massachusetts Institute of Technology 2015-2018
# (c) Brian Teague 2018-2022
#
# 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 2 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 <http://www.gnu.org/licenses/>.

"""
adapted from sphinx.ext.autodoc.mock
"""

import contextlib
import os
import sys
from importlib.abc import Loader, MetaPathFinder
from importlib.machinery import ModuleSpec
from types import FunctionType, MethodType, ModuleType
from typing import Any, Generator, Iterator, List, Sequence, Tuple, Union

import logging

logger = logging.getLogger(__name__)

class _MockObject:
    __display_name__ = '_MockObject'
    __sphinx_mock__ = True

    def __new__(cls, *args: Any, **kwargs: Any) -> Any:
        if len(args) == 3 and isinstance(args[1], tuple):
            superclass = args[1][-1].__class__
            if superclass is cls:
                # subclassing MockObject
                return _make_subclass(args[0], superclass.__display_name__,
                                      superclass=superclass, attributes=args[2])

        return super().__new__(cls)

    def __init__(self, *args: Any, **kwargs: Any) -> None:
        self.__qualname__ = ''

    def __len__(self) -> int:
        return 0

    def __contains__(self, key: str) -> bool:
        return False

    def __iter__(self) -> Iterator:
        return iter([])

    def __mro_entries__(self, bases: Tuple) -> Tuple:
        return (self.__class__,)

    def __getitem__(self, key: Any) -> "_MockObject":
        return _make_subclass(str(key), self.__display_name__, self.__class__)()

    def __getattr__(self, key: str) -> "_MockObject":
        return _make_subclass(key, self.__display_name__, self.__class__)()

    def __call__(self, *args: Any, **kwargs: Any) -> Any:
        if args and type(args[0]) in [type, FunctionType, MethodType]:
            # Appears to be a decorator, pass through unchanged
            return args[0]
        return self

    def __repr__(self) -> str:
        return self.__display_name__


def _make_subclass(name: str, module: str, superclass: Any = _MockObject,
                   attributes: Any = None) -> Any:
    attrs = {'__module__': module, '__display_name__': module + '.' + name}
    attrs.update(attributes or {})

    return type(name, (superclass,), attrs)


class _MockModule(ModuleType):
    """Used by autodoc_mock_imports."""
    __file__ = os.devnull
    __sphinx_mock__ = True

    def __init__(self, name: str) -> None:
        super().__init__(name)
        self.__all__ = []  # type: List[str]
        self.__path__ = []  # type: List[str]

    def __getattr__(self, name: str) -> _MockObject:
        return _make_subclass(name, self.__name__)()

    def __repr__(self) -> str:
        return self.__name__


class MockLoader(Loader):
    """A loader for mocking."""
    def __init__(self, finder: "MockFinder") -> None:
        super().__init__()
        self.finder = finder

    def create_module(self, spec: ModuleSpec) -> ModuleType:
        logger.debug('adding a mock module as %s!', spec.name)
        self.finder.mocked_modules.append(spec.name)
        return _MockModule(spec.name)

    def exec_module(self, module: ModuleType) -> None:
        pass  # nothing to do


class MockFinder(MetaPathFinder):
    """A finder for mocking."""

    def __init__(self, modnames: List[str]) -> None:
        super().__init__()
        self.modnames = modnames
        self.loader = MockLoader(self)
        self.mocked_modules = []  # type: List[str]

    def find_spec(self, fullname: str, path: Sequence[Union[bytes, str]],
                  target: ModuleType = None) -> ModuleSpec:
        for modname in self.modnames:
            # check if fullname is (or is a descendant of) one of our targets
            if modname == fullname or fullname.startswith(modname + '.'):
                return ModuleSpec(fullname, self.loader)

        return None

    def invalidate_caches(self) -> None:
        """Invalidate mocked modules on sys.modules."""
        for modname in self.mocked_modules:
            sys.modules.pop(modname, None)


@contextlib.contextmanager
def mock(modnames: List[str]) -> Generator[None, None, None]:
    """Insert mock modules during context::

        with mock(['target.module.name']):
            # mock modules are enabled here
            ...
    """
    try:
        finder = MockFinder(modnames)
        sys.meta_path.insert(0, finder)
        yield
    finally:
        sys.meta_path.remove(finder)
        finder.invalidate_caches()
