import os
import sys
import unittest
from importlib import import_module
from zipimport import zipimporter

from django.test import SimpleTestCase, modify_settings
from django.test.utils import extend_sys_path
from django.utils.module_loading import (
    autodiscover_modules, import_string, module_has_submodule,
)


class DefaultLoader(unittest.TestCase):

    def test_loader(self):
        "Normal module existence can be tested"
        test_module = import_module('utils_tests.test_module')
        test_no_submodule = import_module(
            'utils_tests.test_no_submodule')

        # An importable child
        self.assertTrue(module_has_submodule(test_module, 'good_module'))
        mod = import_module('utils_tests.test_module.good_module')
        self.assertEqual(mod.content, 'Good Module')

        # A child that exists, but will generate an import error if loaded
        self.assertTrue(module_has_submodule(test_module, 'bad_module'))
        with self.assertRaises(ImportError):
            import_module('utils_tests.test_module.bad_module')

        # A child that doesn't exist
        self.assertFalse(module_has_submodule(test_module, 'no_such_module'))
        with self.assertRaises(ImportError):
            import_module('utils_tests.test_module.no_such_module')

        # A child that doesn't exist, but is the name of a package on the path
        self.assertFalse(module_has_submodule(test_module, 'django'))
        with self.assertRaises(ImportError):
            import_module('utils_tests.test_module.django')

        # Don't be confused by caching of import misses
        import types  # NOQA: causes attempted import of utils_tests.types
        self.assertFalse(module_has_submodule(sys.modules['utils_tests'], 'types'))

        # A module which doesn't have a __path__ (so no submodules)
        self.assertFalse(module_has_submodule(test_no_submodule, 'anything'))
        with self.assertRaises(ImportError):
            import_module('utils_tests.test_no_submodule.anything')

    def test_has_sumbodule_with_dotted_path(self):
        """Nested module existence can be tested."""
        test_module = import_module('utils_tests.test_module')
        # A grandchild that exists.
        self.assertIs(module_has_submodule(test_module, 'child_module.grandchild_module'), True)
        # A grandchild that doesn't exist.
        self.assertIs(module_has_submodule(test_module, 'child_module.no_such_module'), False)
        # A grandchild whose parent doesn't exist.
        self.assertIs(module_has_submodule(test_module, 'no_such_module.grandchild_module'), False)
        # A grandchild whose parent is not a package.
        self.assertIs(module_has_submodule(test_module, 'good_module.no_such_module'), False)


class EggLoader(unittest.TestCase):
    def setUp(self):
        self.egg_dir = '%s/eggs' % os.path.dirname(__file__)

    def tearDown(self):
        sys.path_importer_cache.clear()

        sys.modules.pop('egg_module.sub1.sub2.bad_module', None)
        sys.modules.pop('egg_module.sub1.sub2.good_module', None)
        sys.modules.pop('egg_module.sub1.sub2', None)
        sys.modules.pop('egg_module.sub1', None)
        sys.modules.pop('egg_module.bad_module', None)
        sys.modules.pop('egg_module.good_module', None)
        sys.modules.pop('egg_module', None)

    def test_shallow_loader(self):
        "Module existence can be tested inside eggs"
        egg_name = '%s/test_egg.egg' % self.egg_dir
        with extend_sys_path(egg_name):
            egg_module = import_module('egg_module')

            # An importable child
            self.assertTrue(module_has_submodule(egg_module, 'good_module'))
            mod = import_module('egg_module.good_module')
            self.assertEqual(mod.content, 'Good Module')

            # A child that exists, but will generate an import error if loaded
            self.assertTrue(module_has_submodule(egg_module, 'bad_module'))
            with self.assertRaises(ImportError):
                import_module('egg_module.bad_module')

            # A child that doesn't exist
            self.assertFalse(module_has_submodule(egg_module, 'no_such_module'))
            with self.assertRaises(ImportError):
                import_module('egg_module.no_such_module')

    def test_deep_loader(self):
        "Modules deep inside an egg can still be tested for existence"
        egg_name = '%s/test_egg.egg' % self.egg_dir
        with extend_sys_path(egg_name):
            egg_module = import_module('egg_module.sub1.sub2')

            # An importable child
            self.assertTrue(module_has_submodule(egg_module, 'good_module'))
            mod = import_module('egg_module.sub1.sub2.good_module')
            self.assertEqual(mod.content, 'Deep Good Module')

            # A child that exists, but will generate an import error if loaded
            self.assertTrue(module_has_submodule(egg_module, 'bad_module'))
            with self.assertRaises(ImportError):
                import_module('egg_module.sub1.sub2.bad_module')

            # A child that doesn't exist
            self.assertFalse(module_has_submodule(egg_module, 'no_such_module'))
            with self.assertRaises(ImportError):
                import_module('egg_module.sub1.sub2.no_such_module')


class ModuleImportTests(SimpleTestCase):
    def test_import_string(self):
        cls = import_string('django.utils.module_loading.import_string')
        self.assertEqual(cls, import_string)

        # Test exceptions raised
        with self.assertRaises(ImportError):
            import_string('no_dots_in_path')
        msg = 'Module "utils_tests" does not define a "unexistent" attribute'
        with self.assertRaisesMessage(ImportError, msg):
            import_string('utils_tests.unexistent')


@modify_settings(INSTALLED_APPS={'append': 'utils_tests.test_module'})
class AutodiscoverModulesTestCase(SimpleTestCase):

    def tearDown(self):
        sys.path_importer_cache.clear()

        sys.modules.pop('utils_tests.test_module.another_bad_module', None)
        sys.modules.pop('utils_tests.test_module.another_good_module', None)
        sys.modules.pop('utils_tests.test_module.bad_module', None)
        sys.modules.pop('utils_tests.test_module.good_module', None)
        sys.modules.pop('utils_tests.test_module', None)

    def test_autodiscover_modules_found(self):
        autodiscover_modules('good_module')

    def test_autodiscover_modules_not_found(self):
        autodiscover_modules('missing_module')

    def test_autodiscover_modules_found_but_bad_module(self):
        with self.assertRaisesMessage(ImportError, "No module named 'a_package_name_that_does_not_exist'"):
            autodiscover_modules('bad_module')

    def test_autodiscover_modules_several_one_bad_module(self):
        with self.assertRaisesMessage(ImportError, "No module named 'a_package_name_that_does_not_exist'"):
            autodiscover_modules('good_module', 'bad_module')

    def test_autodiscover_modules_several_found(self):
        autodiscover_modules('good_module', 'another_good_module')

    def test_autodiscover_modules_several_found_with_registry(self):
        from .test_module import site
        autodiscover_modules('good_module', 'another_good_module', register_to=site)
        self.assertEqual(site._registry, {'lorem': 'ipsum'})

    def test_validate_registry_keeps_intact(self):
        from .test_module import site
        with self.assertRaisesMessage(Exception, "Some random exception."):
            autodiscover_modules('another_bad_module', register_to=site)
        self.assertEqual(site._registry, {})

    def test_validate_registry_resets_after_erroneous_module(self):
        from .test_module import site
        with self.assertRaisesMessage(Exception, "Some random exception."):
            autodiscover_modules('another_good_module', 'another_bad_module', register_to=site)
        self.assertEqual(site._registry, {'lorem': 'ipsum'})

    def test_validate_registry_resets_after_missing_module(self):
        from .test_module import site
        autodiscover_modules('does_not_exist', 'another_good_module', 'does_not_exist2', register_to=site)
        self.assertEqual(site._registry, {'lorem': 'ipsum'})


class TestFinder:
    def __init__(self, *args, **kwargs):
        self.importer = zipimporter(*args, **kwargs)

    def find_module(self, path):
        importer = self.importer.find_module(path)
        if importer is None:
            return
        return TestLoader(importer)


class TestLoader:
    def __init__(self, importer):
        self.importer = importer

    def load_module(self, name):
        mod = self.importer.load_module(name)
        mod.__loader__ = self
        return mod


class CustomLoader(EggLoader):
    """The Custom Loader test is exactly the same as the EggLoader, but
    it uses a custom defined Loader and Finder that is intentionally
    split into two classes. Although the EggLoader combines both functions
    into one class, this isn't required.
    """
    def setUp(self):
        super().setUp()
        sys.path_hooks.insert(0, TestFinder)
        sys.path_importer_cache.clear()

    def tearDown(self):
        super().tearDown()
        sys.path_hooks.pop(0)