from rpython.annotator.classdesc import ClassDesc, is_mixin

class FakeBookkeeper:
    def __init__(self):
        self.seen = {}
    def getdesc(self, cls):
        if cls not in self.seen:
            self.seen[cls] = ClassDesc(self, cls)
        return self.seen[cls]

def test_getcommonbase():
    class Base(object): pass
    class A(Base):      pass
    class B(A):         pass
    class C(B):         pass
    class D(A):         pass
    bk = FakeBookkeeper()
    dA = bk.getdesc(A)
    dB = bk.getdesc(B)
    dC = bk.getdesc(C)
    dD = bk.getdesc(D)
    assert ClassDesc.getcommonbase([dC, dD]) is dA

def test_is_mixin():
    class Mixin1(object):
        _mixin_ = True

    class A(Mixin1):
        pass

    assert is_mixin(Mixin1)
    assert not is_mixin(A)

def test_immutable_fields_collection():
    class Base(object):
        _immutable_fields_ = ['a']
    class Mixin(object):
        _mixin_ = True
        _immutable_fields_ = ['b']
    class A(Base, Mixin):
        _immutable_fields_ = ['c']
    bk = FakeBookkeeper()
    assert bk.getdesc(A).immutable_fields == {'b', 'c'}