Terry Jones

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


class ControllableDeferred2013(object):

    """A Deferred-like class that takes a regular Twisted Deferred and
    provides a deferred that can be fired at will. If you have a regular
    Twisted Deferred, you can produce a deferred you have more control over
    by using your Deferred instance to make an instance of this class.

    Any time you need to fire a ControllableDeferred2013 instance for any
    reason, call its callback, errback or cancel method. It will fire
    immediately with the value you provide and the original Deferred will
    be cancelled."""

    def __init__(self, originalDeferred):
        self._fired = False
        self._originalDeferred = originalDeferred
        self._newDeferred = Deferred()
        for method in ('addBoth', 'addCallback', 'addCallbacks', 'addErrback',
                       'chainDeferred'):
            setattr(self, method, getattr(self._newDeferred, method))
        originalDeferred.addBoth(self._originalFired)

    def _originalFired(self, result):
        if not self._fired:
            self._fired = True
            self._originalDeferred.chainDeferred(self._newDeferred)

    def cancel(self, value=None):
        if not self._fired:
            self._fired = True
            self._newDeferred.errback(Failure(CancelledError(value)))
            self._originalDeferred.cancel()

    def callback(self, result=None):
        if not self._fired:
            self._fired = True
            self._newDeferred.callback(result)
            self._originalDeferred.cancel()

    def errback(self, fail=None):
        if not self._fired:
            self._fired = True
            self._newDeferred.errback(fail)
            self._originalDeferred.cancel()

    def pause(self):
        self._newDeferred.pause()
        self._originalDeferred.pause()

    def unpause(self):
        self._newDeferred.unpause()
        self._originalDeferred.unpause()