from weakref import ref

cdef inline void observable_set_dispatch(object self) except *:
    cdef Property prop = self.prop
    obj = self.obj()
    if obj is not None:
        prop.dispatch(obj)


class ObservableSet(set):
    # Internal class to observe changes inside a native python set.
    def __init__(self, *largs):
        self.prop = largs[0]
        self.obj = ref(largs[1])
        super(ObservableSet, self).__init__(*largs[2:])

    def __iand__(self, *largs):
        set.__iand__(self, *largs)
        observable_set_dispatch(self)

    def __ior__(self, *largs):
        set.__ior__(self, *largs)
        observable_set_dispatch(self)

    def __isub__(self, *largs):
        set.__isub__(self, *largs)
        observable_set_dispatch(self)

    def __ixor__(self, *largs):
        set.__ixor__(self, *largs)
        observable_set_dispatch(self)

    def add(self, *largs):
        set.add(self, *largs)
        observable_set_dispatch(self)

    def clear(self):
        set.clear(self)
        observable_set_dispatch(self)

    def difference_update(self, *largs):
        set.difference_update(self, *largs)
        observable_set_dispatch(self)

    def discard(self, *largs):
        set.discard(self, *largs)
        observable_set_dispatch(self)

    def intersection_update(self, *largs):
        set.intersection_update(self, *largs)
        observable_set_dispatch(self)

    def pop(self, *largs):
        cdef object result = set.pop(self, *largs)
        observable_set_dispatch(self)
        return result

    def remove(self, *largs):
        set.remove(self, *largs)
        observable_set_dispatch(self)

    def symmetric_difference_update(self, *largs):
        set.symmetric_difference_update(self, *largs)
        observable_set_dispatch(self)

    def update(self, *largs):
        set.update(self, *largs)
        observable_set_dispatch(self)


cdef class SetProperty(Property):
    '''Property that represents a set.

    :Parameters:
        `defaultvalue`: set, defaults to set()
            Specifies the default value of the property.

    .. warning::

        When assigning a set to a :class:`SetProperty`, the set stored in
        the property is a shallow copy of the set and not the original set. This can
        be demonstrated with the following example::

            >>> class MyWidget(Widget):
            >>>     my_set = SetProperty([])

            >>> widget = MyWidget()
            >>> my_set = {1, 5, {'hi': 'hello'}}
            >>> widget.my_set = my_set
            >>> print(my_set is widget.my_set)
            False
            >>> my_set.add(10)
            >>> print(my_set, widget.my_set)
            {1, 5, {'hi': 'hello'}, 10} {1, 5, {'hi': 'hello'}}

        However, changes to nested levels will affect the property as well,
        since the property uses a shallow copy of my_set.

    '''
    def __init__(self, defaultvalue=0, **kw):
        defaultvalue = set() if defaultvalue == 0 else defaultvalue

        super(SetProperty, self).__init__(defaultvalue, **kw)

    cpdef PropertyStorage link(self, EventDispatcher obj, str name):
        Property.link(self, obj, name)
        cdef PropertyStorage ps = obj.__storage[self._name]
        if ps.value is not None:
            ps.value = ObservableSet(self, obj, ps.value)

    cdef check(self, EventDispatcher obj, value, PropertyStorage property_storage):
        if Property.check(self, obj, value, property_storage):
            return True
        if type(value) is not ObservableSet:
            raise ValueError('%s.%s accept only ObservableSet' % (
                obj.__class__.__name__,
                self.name))

    cpdef set(self, EventDispatcher obj, value):
        if value is not None:
            value = ObservableSet(self, obj, value)
        Property.set(self, obj, value)