"""Helper functions for working with signals"""

import logging

from twisted.internet.defer import DeferredList, Deferred
from twisted.python.failure import Failure

from pydispatch.dispatcher import Anonymous, Any, disconnect, getAllReceivers, liveReceivers
from pydispatch.robustapply import robustApply

from scrapy.exceptions import StopDownload
from scrapy.utils.defer import maybeDeferred_coro
from scrapy.utils.log import failure_to_exc_info


logger = logging.getLogger(__name__)


class _IgnoredException(Exception):
    pass


def send_catch_log(signal=Any, sender=Anonymous, *arguments, **named):
    """Like pydispatcher.robust.sendRobust but it also logs errors and returns
    Failures instead of exceptions.
    """
    dont_log = (named.pop('dont_log', _IgnoredException), StopDownload)
    spider = named.get('spider', None)
    responses = []
    for receiver in liveReceivers(getAllReceivers(sender, signal)):
        try:
            response = robustApply(receiver, signal=signal, sender=sender, *arguments, **named)
            if isinstance(response, Deferred):
                logger.error("Cannot return deferreds from signal handler: %(receiver)s",
                             {'receiver': receiver}, extra={'spider': spider})
        except dont_log:
            result = Failure()
        except Exception:
            result = Failure()
            logger.error("Error caught on signal handler: %(receiver)s",
                         {'receiver': receiver},
                         exc_info=True, extra={'spider': spider})
        else:
            result = response
        responses.append((receiver, result))
    return responses


def send_catch_log_deferred(signal=Any, sender=Anonymous, *arguments, **named):
    """Like send_catch_log but supports returning deferreds on signal handlers.
    Returns a deferred that gets fired once all signal handlers deferreds were
    fired.
    """
    def logerror(failure, recv):
        if dont_log is None or not isinstance(failure.value, dont_log):
            logger.error("Error caught on signal handler: %(receiver)s",
                         {'receiver': recv},
                         exc_info=failure_to_exc_info(failure),
                         extra={'spider': spider})
        return failure

    dont_log = named.pop('dont_log', None)
    spider = named.get('spider', None)
    dfds = []
    for receiver in liveReceivers(getAllReceivers(sender, signal)):
        d = maybeDeferred_coro(robustApply, receiver, signal=signal, sender=sender, *arguments, **named)
        d.addErrback(logerror, receiver)
        d.addBoth(lambda result: (receiver, result))
        dfds.append(d)
    d = DeferredList(dfds)
    d.addCallback(lambda out: [x[1] for x in out])
    return d


def disconnect_all(signal=Any, sender=Any):
    """Disconnect all signal handlers. Useful for cleaning up after running
    tests
    """
    for receiver in liveReceivers(getAllReceivers(sender, signal)):
        disconnect(receiver, signal=signal, sender=sender)
