from django.db.models.aggregates import Aggregate
from django.contrib.gis.db.models.fields import GeometryField, ExtentField

__all__ = ['Collect', 'Extent', 'Extent3D', 'MakeLine', 'Union']


class GeoAggregate(Aggregate):
    function = None
    is_extent = False

    def as_sql(self, compiler, connection):
        self.function = connection.ops.spatial_aggregate_name(self.name)
        return super(GeoAggregate, self).as_sql(compiler, connection)

    def as_oracle(self, compiler, connection):
        if not hasattr(self, 'tolerance'):
            self.tolerance = 0.05
        self.extra['tolerance'] = self.tolerance
        if not self.is_extent:
            self.template = '%(function)s(SDOAGGRTYPE(%(expressions)s,%(tolerance)s))'
        return self.as_sql(compiler, connection)

    def prepare(self, query=None, allow_joins=True, reuse=None, summarize=False):
        c = super(GeoAggregate, self).prepare(query, allow_joins, reuse, summarize)
        if not isinstance(self.expressions[0].output_field, GeometryField):
            raise ValueError('Geospatial aggregates only allowed on geometry fields.')
        return c

    def convert_value(self, value, connection, context):
        return connection.ops.convert_geom(value, self.output_field)


class Collect(GeoAggregate):
    name = 'Collect'


class Extent(GeoAggregate):
    name = 'Extent'
    is_extent = '2D'

    def __init__(self, expression, **extra):
        super(Extent, self).__init__(expression, output_field=ExtentField(), **extra)

    def convert_value(self, value, connection, context):
        return connection.ops.convert_extent(value, context.get('transformed_srid'))


class Extent3D(GeoAggregate):
    name = 'Extent3D'
    is_extent = '3D'

    def __init__(self, expression, **extra):
        super(Extent3D, self).__init__(expression, output_field=ExtentField(), **extra)

    def convert_value(self, value, connection, context):
        return connection.ops.convert_extent3d(value, context.get('transformed_srid'))


class MakeLine(GeoAggregate):
    name = 'MakeLine'


class Union(GeoAggregate):
    name = 'Union'