"""This file contains some basic registerers required by application objects

registry to handle registration at startup time.

A registerer is responsible to tell if an object should be registered according

to the application's schema or to already registered object

:organization: Logilab

:copyright: 2006-2009 LOGILAB S.A. (Paris, FRANCE), all rights reserved.

:contact: http://www.logilab.fr/ -- mailto:contact@logilab.fr

"""

__docformat__ = "restructuredtext en"

from cubicweb.selectors import implements

def _accepts_interfaces(obj):

    impl = obj.__select__.search_selector(implements)

    if impl:

        return sorted(impl.expected_ifaces)

    return sorted(getattr(obj, 'accepts_interfaces', ()))

class priority_registerer(registerer):

    """systematically kick previous registered class and register the

    wrapped class (based on the fact that directory containing vobjects

    are loaded from the most generic to the most specific).

    This is usually for templates or startup views where we want to

    keep only the latest in the load path

    """

    def do_it_yourself(self, registered):

        if registered:

            if len(registered) > 1:

                self.warning('priority_registerer found more than one registered objects '

                             '(registerer monkey patch ?)')

            for regobj in registered[:]:

                self.kick(registered, regobj)

        return self.vobject

    def remove_equivalents(self, registered):

        for _obj in registered[:]:

            if self.equivalent(_obj):

                self.kick(registered, _obj)

                break

    def remove_all_equivalents(self, registered):

        for _obj in registered[:]:

            if _obj is self.vobject:

                continue

            if self.equivalent(_obj):

                self.kick(registered, _obj)

    def equivalent(self, other):

        raise NotImplementedError(self, self.vobject)

class accepts_registerer(priority_registerer):

    """register according to the .accepts attribute of the wrapped

    class, which should be a tuple refering some entity's types

    * if no type is defined the application'schema, skip the wrapped

      class

    * if the class defines a requires attribute, each entity type defined

      in the requires list must be in the schema

    * if an object previously registered has equivalent .accepts

      attribute, kick it out

    * register

    """

    def do_it_yourself(self, registered):

        # if object is accepting interface, we have register it now and

        # remove it latter if no object is implementing accepted interfaces

        if _accepts_interfaces(self.vobject):

            return self.vobject

        self.remove_equivalents(registered)

        return self.vobject

    def equivalent(self, other):

        if _accepts_interfaces(self.vobject) != _accepts_interfaces(other):

            return False

        try:

            newaccepts = list(other.accepts)

            for etype in self.vobject.accepts:

                try:

                    newaccepts.remove(etype)

                except ValueError:

                    continue

            if newaccepts:

                other.accepts = tuple(newaccepts)

                return False

            return True

        except AttributeError:

            return False

__all__ = [cls.__name__ for cls in globals().values()

           if isinstance(cls, type) and issubclass(cls, registerer)

           and not cls is registerer]