from django.db.models.sql.aggregates import *

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

from django.contrib.gis.db.models.sql.conversion import GeomField

class GeoAggregate(Aggregate):

    # Default SQL template for spatial aggregates.

    sql_template = '%(function)s(%(field)s)'

    # Conversion class, if necessary.

    conversion_class = None

    # Flags for indicating the type of the aggregate.

    is_extent = False

    def __init__(self, col, source=None, is_summary=False, tolerance=0.05, **extra):

        super(GeoAggregate, self).__init__(col, source, is_summary, **extra)

        # Required by some Oracle aggregates.

        self.tolerance = tolerance

        # Can't use geographic aggregates on non-geometry fields.

        if not isinstance(self.source, GeometryField):

            raise ValueError('Geospatial aggregates only allowed on geometry fields.')

    def as_sql(self, qn, connection):

        "Return the aggregate, rendered as SQL."

        if connection.ops.oracle:

            self.extra['tolerance'] = self.tolerance

        if hasattr(self.col, 'as_sql'):

            field_name = self.col.as_sql(qn, connection)

        elif isinstance(self.col, (list, tuple)):

            field_name = '.'.join([qn(c) for c in self.col])

        else:

            field_name = self.col

        sql_template, sql_function = connection.ops.spatial_aggregate_sql(self)

        params = {

            'function': sql_function,

            'field': field_name

        }

        params.update(self.extra)

        return sql_template % params

class Collect(GeoAggregate):

    pass

class Extent(GeoAggregate):

    is_extent = '2D'

class Extent3D(GeoAggregate):

    is_extent = '3D'

class MakeLine(GeoAggregate):

    pass

class Union(GeoAggregate):

    pass