import abc
import contextlib
import functools
import importlib
import io
import pathlib
import sys
import types
from importlib.abc import Loader, MetaPathFinder
from importlib.machinery import ModuleSpec
from importlib.resources.abc import ResourceReader, Traversable, TraversableResources

from test.support import import_helper, os_helper

from . import _path
from . import zip as zip_


class Reader(ResourceReader):
    def __init__(self, **kwargs):
        vars(self).update(kwargs)

    def get_resource_reader(self, package):
        return self

    def open_resource(self, path):
        self._path = path
        if isinstance(self.file, Exception):
            raise self.file
        return self.file

    def resource_path(self, path_):
        self._path = path_
        if isinstance(self.path, Exception):
            raise self.path
        return self.path

    def is_resource(self, path_):
        self._path = path_
        if isinstance(self.path, Exception):
            raise self.path

        def part(entry):
            return entry.split('/')

        return any(
            len(parts) == 1 and parts[0] == path_ for parts in map(part, self._contents)
        )

    def contents(self):
        if isinstance(self.path, Exception):
            raise self.path
        yield from self._contents


def create_package_from_loader(loader, is_package=True):
    name = 'testingpackage'
    module = types.ModuleType(name)
    spec = ModuleSpec(name, loader, origin='does-not-exist', is_package=is_package)
    module.__spec__ = spec
    module.__loader__ = loader
    return module


def create_package(file=None, path=None, is_package=True, contents=()):
    return create_package_from_loader(
        Reader(file=file, path=path, _contents=contents),
        is_package,
    )


class CommonTestsBase(metaclass=abc.ABCMeta):
    """
    Tests shared by test_open, test_path, and test_read.
    """

    @abc.abstractmethod
    def execute(self, package, path):
        """
        Call the pertinent legacy API function (e.g. open_text, path)
        on package and path.
        """

    def test_package_name(self):
        """
        Passing in the package name should succeed.
        """
        self.execute(self.data.__name__, 'utf-8.file')

    def test_package_object(self):
        """
        Passing in the package itself should succeed.
        """
        self.execute(self.data, 'utf-8.file')

    def test_string_path(self):
        """
        Passing in a string for the path should succeed.
        """
        path = 'utf-8.file'
        self.execute(self.data, path)

    def test_pathlib_path(self):
        """
        Passing in a pathlib.PurePath object for the path should succeed.
        """
        path = pathlib.PurePath('utf-8.file')
        self.execute(self.data, path)

    def test_importing_module_as_side_effect(self):
        """
        The anchor package can already be imported.
        """
        del sys.modules[self.data.__name__]
        self.execute(self.data.__name__, 'utf-8.file')

    def test_missing_path(self):
        """
        Attempting to open or read or request the path for a
        non-existent path should succeed if open_resource
        can return a viable data stream.
        """
        bytes_data = io.BytesIO(b'Hello, world!')
        package = create_package(file=bytes_data, path=FileNotFoundError())
        self.execute(package, 'utf-8.file')
        assert package.__loader__._path == 'utf-8.file'

    def test_extant_path(self):
        # Attempting to open or read or request the path when the
        # path does exist should still succeed. Does not assert
        # anything about the result.
        bytes_data = io.BytesIO(b'Hello, world!')
        # any path that exists
        path = __file__
        package = create_package(file=bytes_data, path=path)
        self.execute(package, 'utf-8.file')
        assert package.__loader__._path == 'utf-8.file'

    def test_useless_loader(self):
        package = create_package(file=FileNotFoundError(), path=FileNotFoundError())
        with self.assertRaises(FileNotFoundError):
            self.execute(package, 'utf-8.file')


fixtures = dict(
    data01={
        '__init__.py': '',
        'binary.file': bytes(range(4)),
        'utf-16.file': '\ufeffHello, UTF-16 world!\n'.encode('utf-16-le'),
        'utf-8.file': 'Hello, UTF-8 world!\n'.encode('utf-8'),
        'subdirectory': {
            '__init__.py': '',
            'binary.file': bytes(range(4, 8)),
        },
    },
    data02={
        '__init__.py': '',
        'one': {'__init__.py': '', 'resource1.txt': 'one resource'},
        'two': {'__init__.py': '', 'resource2.txt': 'two resource'},
        'subdirectory': {'subsubdir': {'resource.txt': 'a resource'}},
    },
    namespacedata01={
        'binary.file': bytes(range(4)),
        'utf-16.file': '\ufeffHello, UTF-16 world!\n'.encode('utf-16-le'),
        'utf-8.file': 'Hello, UTF-8 world!\n'.encode('utf-8'),
        'subdirectory': {
            'binary.file': bytes(range(12, 16)),
        },
    },
)


class ModuleSetup:
    def setUp(self):
        self.fixtures = contextlib.ExitStack()
        self.addCleanup(self.fixtures.close)

        self.fixtures.enter_context(import_helper.isolated_modules())
        self.data = self.load_fixture(self.MODULE)

    def load_fixture(self, module):
        self.tree_on_path({module: fixtures[module]})
        return importlib.import_module(module)


class ZipSetup(ModuleSetup):
    MODULE = 'data01'

    def tree_on_path(self, spec):
        temp_dir = self.fixtures.enter_context(os_helper.temp_dir())
        modules = pathlib.Path(temp_dir) / 'zipped modules.zip'
        self.fixtures.enter_context(
            import_helper.DirsOnSysPath(str(zip_.make_zip_file(spec, modules)))
        )


class DiskSetup(ModuleSetup):
    MODULE = 'data01'

    def tree_on_path(self, spec):
        temp_dir = self.fixtures.enter_context(os_helper.temp_dir())
        _path.build(spec, pathlib.Path(temp_dir))
        self.fixtures.enter_context(import_helper.DirsOnSysPath(temp_dir))


class MemorySetup(ModuleSetup):
    """Support loading a module in memory."""

    MODULE = 'data01'

    def load_fixture(self, module):
        self.fixtures.enter_context(self.augment_sys_metapath(module))
        return importlib.import_module(module)

    @contextlib.contextmanager
    def augment_sys_metapath(self, module):
        finder_instance = self.MemoryFinder(module)
        sys.meta_path.append(finder_instance)
        yield
        sys.meta_path.remove(finder_instance)

    class MemoryFinder(MetaPathFinder):
        def __init__(self, module):
            self._module = module

        def find_spec(self, fullname, path, target=None):
            if fullname != self._module:
                return None

            return importlib.machinery.ModuleSpec(
                name=fullname,
                loader=MemorySetup.MemoryLoader(self._module),
                is_package=True,
            )

    class MemoryLoader(Loader):
        def __init__(self, module):
            self._module = module

        def exec_module(self, module):
            pass

        def get_resource_reader(self, fullname):
            return MemorySetup.MemoryTraversableResources(self._module, fullname)

    class MemoryTraversableResources(TraversableResources):
        def __init__(self, module, fullname):
            self._module = module
            self._fullname = fullname

        def files(self):
            return MemorySetup.MemoryTraversable(self._module, self._fullname)

    class MemoryTraversable(Traversable):
        """Implement only the abstract methods of `Traversable`.

        Besides `.__init__()`, no other methods may be implemented or overridden.
        This is critical for validating the concrete `Traversable` implementations.
        """

        def __init__(self, module, fullname):
            self._module = module
            self._fullname = fullname

        def _resolve(self):
            """
            Fully traverse the `fixtures` dictionary.

            This should be wrapped in a `try/except KeyError`
            but it is not currently needed and lowers the code coverage numbers.
            """
            path = pathlib.PurePosixPath(self._fullname)
            return functools.reduce(lambda d, p: d[p], path.parts, fixtures)

        def iterdir(self):
            directory = self._resolve()
            if not isinstance(directory, dict):
                # Filesystem openers raise OSError, and that exception is mirrored here.
                raise OSError(f"{self._fullname} is not a directory")
            for path in directory:
                yield MemorySetup.MemoryTraversable(
                    self._module, f"{self._fullname}/{path}"
                )

        def is_dir(self) -> bool:
            return isinstance(self._resolve(), dict)

        def is_file(self) -> bool:
            return not self.is_dir()

        def open(self, mode='r', encoding=None, errors=None, *_, **__):
            contents = self._resolve()
            if isinstance(contents, dict):
                # Filesystem openers raise OSError when attempting to open a directory,
                # and that exception is mirrored here.
                raise OSError(f"{self._fullname} is a directory")
            if isinstance(contents, str):
                contents = contents.encode("utf-8")
            result = io.BytesIO(contents)
            if "b" in mode:
                return result
            return io.TextIOWrapper(result, encoding=encoding, errors=errors)

        @property
        def name(self):
            return pathlib.PurePosixPath(self._fullname).name


class CommonTests(DiskSetup, CommonTestsBase):
    pass
