import gc
import sys
import unittest
import collections
import weakref
import operator
import contextlib
import copy
import threading
import time
import random

from test import support
from test.support import script_helper

# Used in ReferencesTestCase.test_ref_created_during_del() .
ref_from_del = None

# Used by FinalizeTestCase as a global that may be replaced by None
# when the interpreter shuts down.
_global_var = 'foobar'

class C:
    def method(self):
        pass


class Callable:
    bar = None

    def __call__(self, x):
        self.bar = x


def create_function():
    def f(): pass
    return f

def create_bound_method():
    return C().method


class Object:
    def __init__(self, arg):
        self.arg = arg
    def __repr__(self):
        return "<Object %r>" % self.arg
    def __eq__(self, other):
        if isinstance(other, Object):
            return self.arg == other.arg
        return NotImplemented
    def __lt__(self, other):
        if isinstance(other, Object):
            return self.arg < other.arg
        return NotImplemented
    def __hash__(self):
        return hash(self.arg)
    def some_method(self):
        return 4
    def other_method(self):
        return 5


class RefCycle:
    def __init__(self):
        self.cycle = self


class TestBase(unittest.TestCase):

    def setUp(self):
        self.cbcalled = 0

    def callback(self, ref):
        self.cbcalled += 1


@contextlib.contextmanager
def collect_in_thread(period=0.0001):
    """
    Ensure GC collections happen in a different thread, at a high frequency.
    """
    please_stop = False

    def collect():
        while not please_stop:
            time.sleep(period)
            gc.collect()

    with support.disable_gc():
        t = threading.Thread(target=collect)
        t.start()
        try:
            yield
        finally:
            please_stop = True
            t.join()


class ReferencesTestCase(TestBase):

    def test_basic_ref(self):
        self.check_basic_ref(C)
        self.check_basic_ref(create_function)
        self.check_basic_ref(create_bound_method)

        # Just make sure the tp_repr handler doesn't raise an exception.
        # Live reference:
        o = C()
        wr = weakref.ref(o)
        repr(wr)
        # Dead reference:
        del o
        repr(wr)

    def test_basic_callback(self):
        self.check_basic_callback(C)
        self.check_basic_callback(create_function)
        self.check_basic_callback(create_bound_method)

    @support.cpython_only
    def test_cfunction(self):
        import _testcapi
        create_cfunction = _testcapi.create_cfunction
        f = create_cfunction()
        wr = weakref.ref(f)
        self.assertIs(wr(), f)
        del f
        self.assertIsNone(wr())
        self.check_basic_ref(create_cfunction)
        self.check_basic_callback(create_cfunction)

    def test_multiple_callbacks(self):
        o = C()
        ref1 = weakref.ref(o, self.callback)
        ref2 = weakref.ref(o, self.callback)
        del o
        self.assertIsNone(ref1(), "expected reference to be invalidated")
        self.assertIsNone(ref2(), "expected reference to be invalidated")
        self.assertEqual(self.cbcalled, 2,
                     "callback not called the right number of times")

    def test_multiple_selfref_callbacks(self):
        # Make sure all references are invalidated before callbacks are called
        #
        # What's important here is that we're using the first
        # reference in the callback invoked on the second reference
        # (the most recently created ref is cleaned up first).  This
        # tests that all references to the object are invalidated
        # before any of the callbacks are invoked, so that we only
        # have one invocation of _weakref.c:cleanup_helper() active
        # for a particular object at a time.
        #
        def callback(object, self=self):
            self.ref()
        c = C()
        self.ref = weakref.ref(c, callback)
        ref1 = weakref.ref(c, callback)
        del c

    def test_constructor_kwargs(self):
        c = C()
        self.assertRaises(TypeError, weakref.ref, c, callback=None)

    def test_proxy_ref(self):
        o = C()
        o.bar = 1
        ref1 = weakref.proxy(o, self.callback)
        ref2 = weakref.proxy(o, self.callback)
        del o

        def check(proxy):
            proxy.bar

        self.assertRaises(ReferenceError, check, ref1)
        self.assertRaises(ReferenceError, check, ref2)
        self.assertRaises(ReferenceError, bool, weakref.proxy(C()))
        self.assertEqual(self.cbcalled, 2)

    def check_basic_ref(self, factory):
        o = factory()
        ref = weakref.ref(o)
        self.assertIsNotNone(ref(),
                     "weak reference to live object should be live")
        o2 = ref()
        self.assertIs(o, o2,
                     "<ref>() should return original object if live")

    def check_basic_callback(self, factory):
        self.cbcalled = 0
        o = factory()
        ref = weakref.ref(o, self.callback)
        del o
        self.assertEqual(self.cbcalled, 1,
                     "callback did not properly set 'cbcalled'")
        self.assertIsNone(ref(),
                     "ref2 should be dead after deleting object reference")

    def test_ref_reuse(self):
        o = C()
        ref1 = weakref.ref(o)
        # create a proxy to make sure that there's an intervening creation
        # between these two; it should make no difference
        proxy = weakref.proxy(o)
        ref2 = weakref.ref(o)
        self.assertIs(ref1, ref2,
                     "reference object w/out callback should be re-used")

        o = C()
        proxy = weakref.proxy(o)
        ref1 = weakref.ref(o)
        ref2 = weakref.ref(o)
        self.assertIs(ref1, ref2,
                     "reference object w/out callback should be re-used")
        self.assertEqual(weakref.getweakrefcount(o), 2,
                     "wrong weak ref count for object")
        del proxy
        self.assertEqual(weakref.getweakrefcount(o), 1,
                     "wrong weak ref count for object after deleting proxy")

    def test_proxy_reuse(self):
        o = C()
        proxy1 = weakref.proxy(o)
        ref = weakref.ref(o)
        proxy2 = weakref.proxy(o)
        self.assertIs(proxy1, proxy2,
                     "proxy object w/out callback should have been re-used")

    def test_basic_proxy(self):
        o = C()
        self.check_proxy(o, weakref.proxy(o))

        L = collections.UserList()
        p = weakref.proxy(L)
        self.assertFalse(p, "proxy for empty UserList should be false")
        p.append(12)
        self.assertEqual(len(L), 1)
        self.assertTrue(p, "proxy for non-empty UserList should be true")
        p[:] = [2, 3]
        self.assertEqual(len(L), 2)
        self.assertEqual(len(p), 2)
        self.assertIn(3, p, "proxy didn't support __contains__() properly")
        p[1] = 5
        self.assertEqual(L[1], 5)
        self.assertEqual(p[1], 5)
        L2 = collections.UserList(L)
        p2 = weakref.proxy(L2)
        self.assertEqual(p, p2)
        ## self.assertEqual(repr(L2), repr(p2))
        L3 = collections.UserList(range(10))
        p3 = weakref.proxy(L3)
        self.assertEqual(L3[:], p3[:])
        self.assertEqual(L3[5:], p3[5:])
        self.assertEqual(L3[:5], p3[:5])
        self.assertEqual(L3[2:5], p3[2:5])

    def test_proxy_unicode(self):
        # See bug 5037
        class C(object):
            def __str__(self):
                return "string"
            def __bytes__(self):
                return b"bytes"
        instance = C()
        self.assertIn("__bytes__", dir(weakref.proxy(instance)))
        self.assertEqual(bytes(weakref.proxy(instance)), b"bytes")

    def test_proxy_index(self):
        class C:
            def __index__(self):
                return 10
        o = C()
        p = weakref.proxy(o)
        self.assertEqual(operator.index(p), 10)

    def test_proxy_div(self):
        class C:
            def __floordiv__(self, other):
                return 42
            def __ifloordiv__(self, other):
                return 21
        o = C()
        p = weakref.proxy(o)
        self.assertEqual(p // 5, 42)
        p //= 5
        self.assertEqual(p, 21)

    def test_proxy_matmul(self):
        class C:
            def __matmul__(self, other):
                return 1729
            def __rmatmul__(self, other):
                return -163
            def __imatmul__(self, other):
                return 561
        o = C()
        p = weakref.proxy(o)
        self.assertEqual(p @ 5, 1729)
        self.assertEqual(5 @ p, -163)
        p @= 5
        self.assertEqual(p, 561)

    # The PyWeakref_* C API is documented as allowing either NULL or
    # None as the value for the callback, where either means "no
    # callback".  The "no callback" ref and proxy objects are supposed
    # to be shared so long as they exist by all callers so long as
    # they are active.  In Python 2.3.3 and earlier, this guarantee
    # was not honored, and was broken in different ways for
    # PyWeakref_NewRef() and PyWeakref_NewProxy().  (Two tests.)

    def test_shared_ref_without_callback(self):
        self.check_shared_without_callback(weakref.ref)

    def test_shared_proxy_without_callback(self):
        self.check_shared_without_callback(weakref.proxy)

    def check_shared_without_callback(self, makeref):
        o = Object(1)
        p1 = makeref(o, None)
        p2 = makeref(o, None)
        self.assertIs(p1, p2, "both callbacks were None in the C API")
        del p1, p2
        p1 = makeref(o)
        p2 = makeref(o, None)
        self.assertIs(p1, p2, "callbacks were NULL, None in the C API")
        del p1, p2
        p1 = makeref(o)
        p2 = makeref(o)
        self.assertIs(p1, p2, "both callbacks were NULL in the C API")
        del p1, p2
        p1 = makeref(o, None)
        p2 = makeref(o)
        self.assertIs(p1, p2, "callbacks were None, NULL in the C API")

    def test_callable_proxy(self):
        o = Callable()
        ref1 = weakref.proxy(o)

        self.check_proxy(o, ref1)

        self.assertIs(type(ref1), weakref.CallableProxyType,
                     "proxy is not of callable type")
        ref1('twinkies!')
        self.assertEqual(o.bar, 'twinkies!',
                     "call through proxy not passed through to original")