from django.db.models.query import sql

from django.contrib.gis.db.models.fields import GeometryField

from django.contrib.gis.db.models.sql.conversion import AreaField, DistanceField, GeomField

from django.contrib.gis.db.models.sql.where import GeoWhereNode

from django.contrib.gis.measure import Area, Distance

class GeoQuery(sql.Query):

    """

    A single spatial SQL query.

    """

    # Overridding the valid query terms.

    query_terms = ALL_TERMS

    #### Methods overridden from the base Query class ####

        # The following attributes are customized for the GeoQuerySet.

        # The GeoWhereNode and SpatialBackend classes contain backend-specific

        # routines and functions.

        self.custom_select = {}

        self.transformed_srid = None

        self.extra_select_fields = {}

    def clone(self, *args, **kwargs):

        obj = super(GeoQuery, self).clone(*args, **kwargs)

        # Customized selection dictionary and transformed srid flag have

        # to also be added to obj.

        obj.custom_select = self.custom_select.copy()

        obj.transformed_srid = self.transformed_srid

        obj.extra_select_fields = self.extra_select_fields.copy()

        return obj

        """

        Using the same routines that Oracle does we can convert our

        extra selection objects into Geometry and Distance objects.

        TODO: Make converted objects 'lazy' for less overhead.

        """

            # Running through Oracle's first.

            # Using the field's distance attribute, can instantiate

            # `Distance` with the right context.

            value = Distance(**{field.distance_att : value})

        elif isinstance(field, AreaField):

            value = Area(**{field.area_att : value})

        elif isinstance(field, (GeomField, GeometryField)) and value:

        return value

        """

        Overridden from GeoQuery's normalize to handle the conversion of

        GeoAggregate objects.

        """

        if isinstance(aggregate, self.aggregates_module.GeoAggregate):

            if aggregate.is_extent:

            else:

        else:

    # Private API utilities, subject to change.

    def _geo_field(self, field_name=None):

        """

        Returns the first Geometry field encountered; or specified via the

        `field_name` keyword.  The `field_name` may be a string specifying

        the geometry field on this GeoQuery's model, or a lookup string

        to a geometry field via a ForeignKey relation.

        """

        if field_name is None:

            # Incrementing until the first geographic field is found.

            for fld in self.model._meta.fields:

                if isinstance(fld, GeometryField): return fld

            return False

        else:

            # Otherwise, check by the given field name -- which may be

            # a lookup to a _related_ geographic field.

            return GeoWhereNode._check_geo_field(self.model._meta, field_name)