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

from django.contrib.gis.db.backend import SpatialBackend

# Default SQL template for spatial aggregates.

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

# Default conversion functions for aggregates; will be overridden if implemented

# for the spatial backend.

def convert_extent(box):

    raise NotImplementedError('Aggregate extent not implemented for this spatial backend.')

def convert_geom(wkt, geo_field):

    raise NotImplementedError('Aggregate method not implemented for this spatial backend.')

if SpatialBackend.postgis:

    def convert_extent(box):

        # Box text will be something like "BOX(-90.0 30.0, -85.0 40.0)";

        # parsing out and returning as a 4-tuple.

        ll, ur = box[4:-1].split(',')

        xmin, ymin = map(float, ll.split())

        xmax, ymax = map(float, ur.split())

        return (xmin, ymin, xmax, ymax)

    def convert_geom(hex, geo_field):

        if hex: return SpatialBackend.Geometry(hex)

        else: return None

elif SpatialBackend.oracle:

    # Oracle spatial aggregates need a tolerance.

    geo_template = '%(function)s(SDOAGGRTYPE(%(field)s,%(tolerance)s))'

    def convert_extent(clob):

        if clob:

            # Generally, Oracle returns a polygon for the extent -- however,

            # it can return a single point if there's only one Point in the

            # table.

            ext_geom = SpatialBackend.Geometry(clob.read())

            gtype = str(ext_geom.geom_type)

            if gtype == 'Polygon':

                # Construct the 4-tuple from the coordinates in the polygon.

                shell = ext_geom.shell

                ll, ur = shell[0][:2], shell[2][:2]

            elif gtype == 'Point':

                ll = ext_geom.coords[:2]

                ur = ll

            else:

                raise Exception('Unexpected geometry type returned for extent: %s' % gtype)

            xmin, ymin = ll

            xmax, ymax = ur

            return (xmin, ymin, xmax, ymax)

        else:

            return None

    def convert_geom(clob, geo_field):

        if clob:

            return SpatialBackend.Geometry(clob.read(), geo_field.srid)

        else:

            return None

elif SpatialBackend.spatialite:

    # SpatiaLite returns WKT.

    def convert_geom(wkt, geo_field):

        if wkt:

            return SpatialBackend.Geometry(wkt, geo_field.srid)

        else:

            return None

class GeoAggregate(Aggregate):

    # Overriding the SQL template with the geographic one.

    sql_template = geo_template

    # 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, **extra):

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

        if not self.is_extent and SpatialBackend.oracle:

            self.extra.setdefault('tolerance', 0.05)

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

        if not isinstance(self.source, GeometryField):

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

        # Making sure the SQL function is available for this spatial backend.

        if not self.sql_function:

            raise NotImplementedError('This aggregate functionality not implemented for your spatial backend.')

class Collect(GeoAggregate):

    conversion_class = GeomField

    sql_function = SpatialBackend.collect

class Extent(GeoAggregate):

    is_extent = True

    sql_function = SpatialBackend.extent

if SpatialBackend.oracle:

    # Have to change Extent's attributes here for Oracle.

    Extent.conversion_class = GeomField

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

class MakeLine(GeoAggregate):

    conversion_class = GeomField

    sql_function = SpatialBackend.make_line

class Union(GeoAggregate):

    conversion_class = GeomField

    sql_function = SpatialBackend.unionagg