from celery.utils import instantiate
from celery.exceptions import RouteNotFound


# Route from mapping
class MapRoute(object):

    def __init__(self, map):
        self.map = map

    def route_for_task(self, task, *args, **kwargs):
        return self.map.get(task)


def expand_destination(route, routing_table):
    if isinstance(route, basestring):
        try:
            dest = dict(routing_table[route])
        except KeyError, exc:
            raise RouteNotFound(
                "Route %s does not exist in the routing table "
                "(CELERY_QUEUES)" % route)
        dest.setdefault("routing_key", dest.get("binding_key"))
        return dest
    return route


def prepare(routes):
    """Expand ROUTES setting."""

    def expand_route(route):
        if isinstance(route, dict):
            return MapRoute(route)
        if isinstance(route, basestring):
            return instantiate(route)
        return route

    if not hasattr(routes, "__iter__"):
        routes = (routes, )
    return map(expand_route, routes)


def firstmatcher(method):
    """With a list of instances, find the first instance that returns a
    value for the given method."""

    def _matcher(seq, *args, **kwargs):
        for cls in seq:
            try:
                answer = getattr(cls, method)(*args, **kwargs)
                if answer is not None:
                    return answer
            except AttributeError:
                pass
    return _matcher


_first_route = firstmatcher("route_for_task")
_first_disabled = firstmatcher("disabled")


def lookup_route(routes, task, task_id=None, args=None, kwargs=None):
    return _first_route(routes, task, task_id, args, kwargs)


def lookup_disabled(routes, task, task_id=None, args =None, kwargs=None):
    return _first_disabled(routes, task, task_id, args, kwargs)