from copy import copy

_MARKER = object()

class dict_protocol_catcher(object):

    def __init__(self, entity):

        self.__entity = entity

    def __getitem__(self, attr):

        return self.__entity.cw_edited[attr]

    def __setitem__(self, attr, value):

        self.__entity.cw_edited[attr] = value

    def __getattr__(self, attr):

        return getattr(self.__entity, attr)

class EditedEntity(dict):

    """encapsulate entities attributes being written by an RQL query"""

    def __init__(self, entity, **kwargs):

        dict.__init__(self, **kwargs)

        self.entity = entity

        self.skip_security = set()

        self.querier_pending_relations = {}

        self.saved = False

    def __hash__(self):

        # dict|set keyable

        return hash(id(self))

    def __cmp__(self, other):

        # we don't want comparison by value inherited from dict

        return cmp(id(self), id(other))

    def __setitem__(self, attr, value):

        assert attr != 'eid'

        # don't add attribute into skip_security if already in edited

        # attributes, else we may accidentaly skip a desired security check

        if attr not in self:

            self.skip_security.add(attr)

        self.edited_attribute(attr, value)

    def __delitem__(self, attr):

        assert not self.saved, 'too late to modify edited attributes'

        super(EditedEntity, self).__delitem__(attr)

        self.entity.cw_attr_cache.pop(attr, None)

    def pop(self, attr, *args):

        # don't update skip_security by design (think to storage api)

        assert not self.saved, 'too late to modify edited attributes'

        value = super(EditedEntity, self).pop(attr, *args)

        self.entity.cw_attr_cache.pop(attr, *args)

        return value

    def setdefault(self, attr, default):

        assert attr != 'eid'

        # don't add attribute into skip_security if already in edited

        # attributes, else we may accidentaly skip a desired security check

        if attr not in self:

            self[attr] = default

        return self[attr]

    def update(self, values, skipsec=True):

        if skipsec:

            setitem = self.__setitem__

        else:

            setitem = self.edited_attribute

        for attr, value in values.iteritems():

            setitem(attr, value)

    def edited_attribute(self, attr, value):

        """attribute being edited by a rql query: should'nt be added to

        skip_security

        """

        assert not self.saved, 'too late to modify edited attributes'

        super(EditedEntity, self).__setitem__(attr, value)

        self.entity.cw_attr_cache[attr] = value

    def oldnewvalue(self, attr):

        """returns the couple (old attr value, new attr value)

        NOTE: will only work in a before_update_entity hook

        """

        assert not self.saved, 'too late to get the old value'

        # get new value and remove from local dict to force a db query to

        # fetch old value

        newvalue = self.entity.cw_attr_cache.pop(attr, _MARKER)

        oldvalue = getattr(self.entity, attr)

        if newvalue is not _MARKER:

            self.entity.cw_attr_cache[attr] = newvalue

        else:

            newvalue = oldvalue

        return oldvalue, newvalue

    def set_defaults(self):

        """set default values according to the schema"""

        for attr, value in self.entity.e_schema.defaults():

            if not attr in self:

                self[str(attr)] = value

    def check(self, creation=False):

        """check the entity edition against its schema. Only final relation

        are checked here, constraint on actual relations are checked in hooks

        """

        entity = self.entity

        if creation:

            # on creations, we want to check all relations, especially

            # required attributes

            relations = [rschema for rschema in entity.e_schema.subject_relations()

                         if rschema.final and rschema.type != 'eid']

        else:

            relations = [entity._cw.vreg.schema.rschema(rtype)

                         for rtype in self]

        try:

            entity.e_schema.check(dict_protocol_catcher(entity),

                                  creation=creation, _=entity._cw._,

                                  relations=relations)

        except ValidationError, ex:

            ex.entity = self.entity

            raise

    def clone(self):

        thecopy = EditedEntity(copy(self.entity))

        thecopy.entity.cw_attr_cache = copy(self.entity.cw_attr_cache)

        thecopy.entity._cw_related_cache = {}

        thecopy.update(self, skipsec=False)

        return thecopy