from ctypes import *
import array
import gc
import unittest

class X(Structure):
    _fields_ = [("c_int", c_int)]
    init_called = False
    def __init__(self):
        self._init_called = True

class Test(unittest.TestCase):
    def test_from_buffer(self):
        a = array.array("i", range(16))
        x = (c_int * 16).from_buffer(a)

        y = X.from_buffer(a)
        self.assertEqual(y.c_int, a[0])
        self.assertFalse(y.init_called)

        self.assertEqual(x[:], a.tolist())

        a[0], a[-1] = 200, -200
        self.assertEqual(x[:], a.tolist())

        self.assertRaises(BufferError, a.append, 100)
        self.assertRaises(BufferError, a.pop)

        del x; del y; gc.collect(); gc.collect(); gc.collect()
        a.append(100)
        a.pop()
        x = (c_int * 16).from_buffer(a)

        self.assertIn(a, [obj.obj if isinstance(obj, memoryview) else obj
                          for obj in x._objects.values()])

        expected = x[:]
        del a; gc.collect(); gc.collect(); gc.collect()
        self.assertEqual(x[:], expected)

        with self.assertRaisesRegex(TypeError, "not writable"):
            (c_char * 16).from_buffer(b"a" * 16)
        with self.assertRaisesRegex(TypeError, "not writable"):
            (c_char * 16).from_buffer(memoryview(b"a" * 16))
        with self.assertRaisesRegex(TypeError, "not C contiguous"):
            (c_char * 16).from_buffer(memoryview(bytearray(b"a" * 16))[::-1])
        msg = "does not have the buffer interface"
        with self.assertRaisesRegex(TypeError, msg):
            (c_char * 16).from_buffer("a" * 16)

    def test_fortran_contiguous(self):
        try:
            import _testbuffer
        except ImportError as err:
            self.skipTest(str(err))
        flags = _testbuffer.ND_WRITABLE | _testbuffer.ND_FORTRAN
        array = _testbuffer.ndarray(
            [97] * 16, format="B", shape=[4, 4], flags=flags)
        with self.assertRaisesRegex(TypeError, "not C contiguous"):
            (c_char * 16).from_buffer(array)
        array = memoryview(array)
        self.assertTrue(array.f_contiguous)
        self.assertFalse(array.c_contiguous)
        with self.assertRaisesRegex(TypeError, "not C contiguous"):
            (c_char * 16).from_buffer(array)

    def test_from_buffer_with_offset(self):
        a = array.array("i", range(16))
        x = (c_int * 15).from_buffer(a, sizeof(c_int))

        self.assertEqual(x[:], a.tolist()[1:])
        with self.assertRaises(ValueError):
            c_int.from_buffer(a, -1)
        with self.assertRaises(ValueError):
            (c_int * 16).from_buffer(a, sizeof(c_int))
        with self.assertRaises(ValueError):
            (c_int * 1).from_buffer(a, 16 * sizeof(c_int))

    def test_from_buffer_memoryview(self):
        a = [c_char.from_buffer(memoryview(bytearray(b'a')))]
        a.append(a)
        del a
        gc.collect()  # Should not crash

    def test_from_buffer_copy(self):
        a = array.array("i", range(16))
        x = (c_int * 16).from_buffer_copy(a)

        y = X.from_buffer_copy(a)
        self.assertEqual(y.c_int, a[0])
        self.assertFalse(y.init_called)

        self.assertEqual(x[:], list(range(16)))

        a[0], a[-1] = 200, -200
        self.assertEqual(x[:], list(range(16)))

        a.append(100)
        self.assertEqual(x[:], list(range(16)))

        self.assertEqual(x._objects, None)

        del a; gc.collect(); gc.collect(); gc.collect()
        self.assertEqual(x[:], list(range(16)))

        x = (c_char * 16).from_buffer_copy(b"a" * 16)
        self.assertEqual(x[:], b"a" * 16)
        with self.assertRaises(TypeError):
            (c_char * 16).from_buffer_copy("a" * 16)

    def test_from_buffer_copy_with_offset(self):
        a = array.array("i", range(16))
        x = (c_int * 15).from_buffer_copy(a, sizeof(c_int))

        self.assertEqual(x[:], a.tolist()[1:])
        with self.assertRaises(ValueError):
            c_int.from_buffer_copy(a, -1)
        with self.assertRaises(ValueError):
            (c_int * 16).from_buffer_copy(a, sizeof(c_int))
        with self.assertRaises(ValueError):
            (c_int * 1).from_buffer_copy(a, 16 * sizeof(c_int))

if __name__ == '__main__':
    unittest.main()
