from django.db import connection, transaction

from django.db.models import signals, get_model

from django.db.models.related import RelatedObject

from django.db.models.query_utils import QueryWrapper

from django.utils.translation import ugettext_lazy, string_concat, ungettext, ugettext as _

from django.utils.functional import curry

try:

    set

except NameError:

    from sets import Set as set   # Python 2.3 fallback

RECURSIVE_RELATIONSHIP_CONSTANT = 'self'

pending_lookups = {}

    """

    Adds a lookup on ``cls`` when a related field is defined using a string,

    i.e.::

        class MyModel(Model):

            fk = ForeignKey("AnotherModel")

    This string can be:

        * RECURSIVE_RELATIONSHIP_CONSTANT (i.e. "self") to indicate a recursive

          relation.

        * The name of a model (i.e "AnotherModel") to indicate another model in

          the same app.

        * An app-label and model name (i.e. "someapp.AnotherModel") to indicate

          another model in a different app.

    If the other model hasn't yet been loaded -- almost a given if you're using

    lazy relationships -- then the relation won't be set up until the

    class_prepared signal fires at the end of model initialization.

    """

    # Check for recursive relations

    if relation == RECURSIVE_RELATIONSHIP_CONSTANT:

        app_label = cls._meta.app_label

        model_name = cls.__name__

    else:

        # Look for an "app.Model" relation

        try:

            app_label, model_name = relation.split(".")

        except ValueError:

            # If we can't split, assume a model in current app

            app_label = cls._meta.app_label

            model_name = relation

    # Try to look up the related model, and if it's already loaded resolve the

    # string right away. If get_model returns None, it means that the related

    # model isn't loaded yet, so we need to pend the relation until the class

    # is prepared.

    model = get_model(app_label, model_name, False)

    if model:

    else:

        key = (app_label, model_name)

        pending_lookups.setdefault(key, []).append(value)

    """

    Handle any pending relations to the sending model. Sent from class_prepared.

    """

    key = (sender._meta.app_label, sender.__name__)

#HACK

class RelatedField(object):

    def contribute_to_class(self, cls, name):

        sup = super(RelatedField, self)

        # Add an accessor to allow easy determination of the related query path for this field

        self.related_query_name = curry(self._get_related_query_name, cls._meta)

        if hasattr(sup, 'contribute_to_class'):

            sup.contribute_to_class(cls, name)

        if not cls._meta.abstract and self.rel.related_name:

            self.rel.related_name = self.rel.related_name % {'class': cls.__name__.lower()}

    def set_attributes_from_rel(self):

        self.name = self.name or (self.rel.to._meta.object_name.lower() + '_' + self.rel.to._meta.pk.name)

        self.rel.field_name = self.rel.field_name or self.rel.to._meta.pk.name

    def do_related_class(self, other, cls):

        self.set_attributes_from_rel()

        related = RelatedObject(other, cls, self)

    def get_db_prep_lookup(self, lookup_type, value):

        # If we are doing a lookup on a Related Field, we must be

        # comparing object instances. The value should be the PK of value,

        # not value itself.

        def pk_trace(value):

            # Value may be a primary key, or an object held in a relation.

            # If it is an object, then we need to get the primary key value for

            # that object. In certain conditions (especially one-to-one relations),

            # the primary key may itself be an object - so we need to keep drilling

            # down until we hit a value that can be used for a comparison.

            try:

                while True:

            except AttributeError:

                pass

            return v

        if hasattr(value, 'as_sql'):

            sql, params = value.as_sql()

            return QueryWrapper(('(%s)' % sql), params)

            return [pk_trace(value)]

            return [pk_trace(v) for v in value]

        elif lookup_type == 'isnull':

            return []

        raise TypeError, "Related Field has invalid lookup: %s" % lookup_type

    def _get_related_query_name(self, opts):

        # This method defines the name that can be used to identify this

        # related object in a table-spanning query. It uses the lower-cased

        # object_name by default, but this can be overridden with the

        # "related_name" option.

        return self.rel.related_name or opts.object_name.lower()

class SingleRelatedObjectDescriptor(object):

    # This class provides the functionality that makes the related-object

    # managers available as attributes on a model class, for fields that have

    # a single "remote" value, on the class pointed to by a related field.

    # In the example "place.restaurant", the restaurant attribute is a

    # SingleRelatedObjectDescriptor instance.

    def __init__(self, related):

        self.related = related

        self.cache_name = '_%s_cache' % related.get_accessor_name()

    def __get__(self, instance, instance_type=None):

        if instance is None:

            raise AttributeError, "%s must be accessed via instance" % self.related.opts.object_name

        try:

            return getattr(instance, self.cache_name)

        except AttributeError:

            params = {'%s__pk' % self.related.field.name: instance._get_pk_val()}

            rel_obj = self.related.model._default_manager.get(**params)

            setattr(instance, self.cache_name, rel_obj)

            return rel_obj

    def __set__(self, instance, value):

        if instance is None:

            raise AttributeError, "%s must be accessed via instance" % self.related.opts.object_name

        # Set the value of the related field

        setattr(value, self.related.field.rel.get_related_field().attname, instance)

class ReverseSingleRelatedObjectDescriptor(object):

    # This class provides the functionality that makes the related-object

    # managers available as attributes on a model class, for fields that have

    # a single "remote" value, on the class that defines the related field.

    # In the example "choice.poll", the poll attribute is a

    # ReverseSingleRelatedObjectDescriptor instance.

    def __init__(self, field_with_rel):

        self.field = field_with_rel

    def __get__(self, instance, instance_type=None):

        if instance is None:

            raise AttributeError, "%s must be accessed via instance" % self.field.name

        cache_name = self.field.get_cache_name()

        try:

            return getattr(instance, cache_name)

        except AttributeError:

            val = getattr(instance, self.field.attname)

            if val is None:

                # If NULL is an allowed value, return it.

                if self.field.null:

                    return None

                raise self.field.rel.to.DoesNotExist

            other_field = self.field.rel.get_related_field()

            if other_field.rel:

                params = {'%s__pk' % self.field.rel.field_name: val}

            else:

                params = {'%s__exact' % self.field.rel.field_name: val}

            setattr(instance, cache_name, rel_obj)

            return rel_obj

    def __set__(self, instance, value):

        if instance is None:

            raise AttributeError, "%s must be accessed via instance" % self._field.name

        # Set the value of the related field

        try:

            val = getattr(value, self.field.rel.get_related_field().attname)

        except AttributeError:

            val = None

        setattr(instance, self.field.attname, val)

class ForeignRelatedObjectsDescriptor(object):

    # This class provides the functionality that makes the related-object

    # managers available as attributes on a model class, for fields that have

    # multiple "remote" values and have a ForeignKey pointed at them by

    # some other model. In the example "poll.choice_set", the choice_set

    # attribute is a ForeignRelatedObjectsDescriptor instance.

    def __init__(self, related):

        self.related = related   # RelatedObject instance

    def __get__(self, instance, instance_type=None):

        if instance is None:

            raise AttributeError, "Manager must be accessed via instance"

        rel_field = self.related.field

        rel_model = self.related.model

        # Dynamically create a class that subclasses the related

        # model's default manager.

        superclass = self.related.model._default_manager.__class__

        class RelatedManager(superclass):

            def get_query_set(self):

                return superclass.get_query_set(self).filter(**(self.core_filters))

            def add(self, *objs):

                for obj in objs:

                    setattr(obj, rel_field.name, instance)

                    obj.save()

            add.alters_data = True

            def create(self, **kwargs):

            create.alters_data = True

            # remove() and clear() are only provided if the ForeignKey can have a value of null.

            if rel_field.null:

                def remove(self, *objs):

                    val = getattr(instance, rel_field.rel.get_related_field().attname)

                    for obj in objs:

                        # Is obj actually part of this descriptor set?

                        if getattr(obj, rel_field.attname) == val:

                            setattr(obj, rel_field.name, None)

                            obj.save()

                        else:

                            raise rel_field.rel.to.DoesNotExist, "%r is not related to %r." % (obj, instance)

                remove.alters_data = True

                def clear(self):

                    for obj in self.all():

                        setattr(obj, rel_field.name, None)

                        obj.save()

                clear.alters_data = True

        manager = RelatedManager()

        manager.model = self.related.model

        return manager

    def __set__(self, instance, value):

        if instance is None:

            raise AttributeError, "Manager must be accessed via instance"

        manager = self.__get__(instance)

        # If the foreign key can support nulls, then completely clear the related set.

        # Otherwise, just move the named objects into the set.

        if self.related.field.null:

            manager.clear()

        manager.add(*value)

    """Creates a manager that subclasses 'superclass' (which is a Manager)

    and adds behavior for many-to-many related objects."""

    class ManyRelatedManager(superclass):

        def __init__(self, model=None, core_filters=None, instance=None, symmetrical=None,

                join_table=None, source_col_name=None, target_col_name=None):

            super(ManyRelatedManager, self).__init__()

            self.core_filters = core_filters

            self.model = model

            self.symmetrical = symmetrical

            self.instance = instance

            self.join_table = join_table

            self.source_col_name = source_col_name

            self.target_col_name = target_col_name

            self._pk_val = self.instance._get_pk_val()

            if self._pk_val is None:

        def get_query_set(self):

        def clear(self):

            self._clear_items(self.source_col_name)

            # If this is a symmetrical m2m relation to self, clear the mirror entry in the m2m table

            if self.symmetrical:

                self._clear_items(self.target_col_name)

        clear.alters_data = True

        def create(self, **kwargs):

            self.add(new_obj)

            return new_obj

        create.alters_data = True

        def _add_items(self, source_col_name, target_col_name, *objs):

            # join_table: name of the m2m link table

            # source_col_name: the PK colname in join_table for the source object

            # target_col_name: the PK colname in join_table for the target object

            # *objs - objects to add. Either object instances, or primary keys of object instances.

            # If there aren't any objects, there is nothing to do.

            if objs:

                # Check that all the objects are of the right type

                new_ids = set()

                for obj in objs:

                    if isinstance(obj, self.model):

                        new_ids.add(obj._get_pk_val())

                    else:

                        new_ids.add(obj)

                # Add the newly created or already existing objects to the join table.

                # First find out which items are already added, to avoid adding them twice

                cursor = connection.cursor()

                cursor.execute("SELECT %s FROM %s WHERE %s = %%s AND %s IN (%s)" % \

                    (target_col_name, self.join_table, source_col_name,

                    target_col_name, ",".join(['%s'] * len(new_ids))),

                    [self._pk_val] + list(new_ids))

                existing_ids = set([row[0] for row in cursor.fetchall()])

                # Add the ones that aren't there already

                for obj_id in (new_ids - existing_ids):

                    cursor.execute("INSERT INTO %s (%s, %s) VALUES (%%s, %%s)" % \

                        (self.join_table, source_col_name, target_col_name),

                        [self._pk_val, obj_id])

                transaction.commit_unless_managed()

        def _remove_items(self, source_col_name, target_col_name, *objs):

            # source_col_name: the PK colname in join_table for the source object

            # target_col_name: the PK colname in join_table for the target object

            # *objs - objects to remove

            # If there aren't any objects, there is nothing to do.

            if objs:

                # Check that all the objects are of the right type

                old_ids = set()

                for obj in objs:

                    if isinstance(obj, self.model):

                        old_ids.add(obj._get_pk_val())

                    else:

                        old_ids.add(obj)

                # Remove the specified objects from the join table

                cursor = connection.cursor()

                cursor.execute("DELETE FROM %s WHERE %s = %%s AND %s IN (%s)" % \

                    (self.join_table, source_col_name,

                    target_col_name, ",".join(['%s'] * len(old_ids))),

                    [self._pk_val] + list(old_ids))

                transaction.commit_unless_managed()

        def _clear_items(self, source_col_name):

            # source_col_name: the PK colname in join_table for the source object

            cursor = connection.cursor()

            cursor.execute("DELETE FROM %s WHERE %s = %%s" % \

                (self.join_table, source_col_name),

                [self._pk_val])

            transaction.commit_unless_managed()

    return ManyRelatedManager

class ManyRelatedObjectsDescriptor(object):

    # This class provides the functionality that makes the related-object

    # managers available as attributes on a model class, for fields that have

    # multiple "remote" values and have a ManyToManyField pointed at them by

    # some other model (rather than having a ManyToManyField themselves).

    # In the example "publication.article_set", the article_set attribute is a

    # ManyRelatedObjectsDescriptor instance.

    def __init__(self, related):

        self.related = related   # RelatedObject instance

    def __get__(self, instance, instance_type=None):

        if instance is None:

            raise AttributeError, "Manager must be accessed via instance"

        # Dynamically create a class that subclasses the related

        # model's default manager.

        rel_model = self.related.model

        superclass = rel_model._default_manager.__class__

        qn = connection.ops.quote_name

        manager = RelatedManager(

            model=rel_model,

            core_filters={'%s__pk' % self.related.field.name: instance._get_pk_val()},

            instance=instance,

            symmetrical=False,