import ctypes

from unittest import mock

from django.contrib.gis.ptr import CPointerBase

from django.test import SimpleTestCase

class CPointerBaseTests(SimpleTestCase):

    def test(self):

        destructor_mock = mock.Mock()

        class NullPointerException(Exception):

            pass

        class FakeGeom1(CPointerBase):

            null_ptr_exception_class = NullPointerException

        class FakeGeom2(FakeGeom1):

            ptr_type = ctypes.POINTER(ctypes.c_float)

            destructor = destructor_mock

        fg1 = FakeGeom1()

        fg2 = FakeGeom2()

        # These assignments are OK. None is allowed because it's equivalent

        # to the NULL pointer.

        fg1.ptr = fg1.ptr_type()

        fg1.ptr = None

        fg2.ptr = fg2.ptr_type(ctypes.c_float(5.23))

        fg2.ptr = None

        # Because pointers have been set to NULL, an exception is raised on

        # access. Raising an exception is preferable to a segmentation fault

        # that commonly occurs when a C method is given a NULL reference.

        for fg in (fg1, fg2):

            with self.assertRaises(NullPointerException):

                fg.ptr

        # Anything that's either not None or the acceptable pointer type

        # results in a TypeError when trying to assign it to the `ptr` property.

        # Thus, memory addresses (integers) and pointers of the incorrect type

        # (in `bad_ptrs`) aren't allowed.

        bad_ptrs = (5, ctypes.c_char_p(b"foobar"))

        for bad_ptr in bad_ptrs:

            for fg in (fg1, fg2):

                with self.assertRaisesMessage(TypeError, "Incompatible pointer type"):

                    fg.ptr = bad_ptr

        # Object can be deleted without a destructor set.

        fg = FakeGeom1()

        fg.ptr = fg.ptr_type(1)

        del fg

        # A NULL pointer isn't passed to the destructor.

        fg = FakeGeom2()

        fg.ptr = None

        del fg

        self.assertFalse(destructor_mock.called)

        # The destructor is called if set.

        fg = FakeGeom2()

        ptr = fg.ptr_type(ctypes.c_float(1.0))

        fg.ptr = ptr

        del fg

        destructor_mock.assert_called_with(ptr)

    def test_destructor_catches_importerror(self):

        class FakeGeom(CPointerBase):

            destructor = mock.Mock(side_effect=ImportError)

        fg = FakeGeom()

        fg.ptr = fg.ptr_type(1)

        del fg