"""
A collection of utility routines and classes used by the spatial
backends.
"""


class SpatialOperator(object):
    """
    Class encapsulating the behavior specific to a GIS operation (used by lookups).
    """
    sql_template = None

    def __init__(self, op=None, func=None):
        self.op = op
        self.func = func

    @property
    def default_template(self):
        if self.func:
            return '%(func)s(%(lhs)s, %(rhs)s)'
        else:
            return '%(lhs)s %(op)s %(rhs)s'

    def as_sql(self, connection, lookup, template_params, sql_params):
        sql_template = self.sql_template or lookup.sql_template or self.default_template
        template_params.update({'op': self.op, 'func': self.func})
        return sql_template % template_params, sql_params
