from django.contrib.gis.gdal import OGRGeomType

from django.db.backends.sqlite3.introspection import DatabaseIntrospection, FlexibleFieldLookupDict

class GeoFlexibleFieldLookupDict(FlexibleFieldLookupDict):

    """

    Sublcass that includes updates the `base_data_types_reverse` dict

    for geometry field types.

    """

    base_data_types_reverse = FlexibleFieldLookupDict.base_data_types_reverse.copy()

    base_data_types_reverse.update(

        {'point' : 'GeometryField',

         'linestring' : 'GeometryField',

         'polygon' : 'GeometryField',

         'multipoint' : 'GeometryField',

         'multilinestring' : 'GeometryField',

         'multipolygon' : 'GeometryField',

         'geometrycollection' : 'GeometryField',

         })

class SpatiaLiteIntrospection(DatabaseIntrospection):

    data_types_reverse = GeoFlexibleFieldLookupDict()

    def get_geometry_type(self, table_name, geo_col):

        cursor = self.connection.cursor()

        try:

            # Querying the `geometry_columns` table to get additional metadata.

            cursor.execute('SELECT "coord_dimension", "srid", "type" '

                           'FROM "geometry_columns" '

                           'WHERE "f_table_name"=%s AND "f_geometry_column"=%s',

                           (table_name, geo_col))

            row = cursor.fetchone()

            if not row:

                raise Exception('Could not find a geometry column for "%s"."%s"' %

                                (table_name, geo_col))

            # OGRGeomType does not require GDAL and makes it easy to convert

            # from OGC geom type name to Django field.

            field_type = OGRGeomType(row[2]).django

            # Getting any GeometryField keyword arguments that are not the default.

            dim = row[0]

            srid = row[1]

            field_params = {}

            if srid != 4326:

                field_params['srid'] = srid

            if isinstance(dim, basestring) and 'Z' in dim:

                field_params['dim'] = 3

        finally:

            cursor.close()

        return field_type, field_params