from queue import Queue
from threading import Thread, Event

# Sentinel used for shutdown
class ActorExit(Exception):
  pass

class Actor:
  def __init__(self):
    self._mailbox = Queue()

  def send(self, msg):
    '''
    Send a message to the actor
    '''
    self._mailbox.put(msg)

  def recv(self):
    '''
    Receive an incoming message
    '''
    msg = self._mailbox.get()
    if msg is ActorExit:
      raise ActorExit()
    return msg

  def close(self):
    '''
    Close the actor, thus shutting it down
    '''
    self.send(ActorExit)

  def start(self):
    '''
    Start concurrent execution
    '''
    self._terminated = Event()
    t = Thread(target=self._bootstrap)

    t.daemon = True
    t.start()

  def _bootstrap(self):
    try:
      self.run()
    except ActorExit:
      pass
    finally:
      self._terminated.set()

  def join(self):
    self._terminated.wait()

  def run(self):
    '''
    Run method to be implemented by the user
    '''
    while True:
      msg = self.recv()

# Sample ActorTask
class PrintActor(Actor):
  def run(self):
    while True:
      msg = self.recv()
      print('Got:', msg)

# Sample use
p = PrintActor()
p.start()
p.send('Hello')
p.send('World')
p.close()
p.join()

def print_actor():
  while True:

    try:
      msg = yield   # Get a message
      print('Got:', msg)
    except GeneratorExit:
      print('Actor terminating')

# Sample use
p = print_actor()
next(p)   # Advance to the yield (ready to receive)
p.send('Hello')
p.send('World')
p.close()

class TaggedActor(Actor):
  def run(self):
    while True:
       tag, *payload = self.recv()
       getattr(self,'do_'+tag)(*payload)

  # Methods correponding to different message tags
  def do_A(self, x):
    print('Running A', x)

  def do_B(self, x, y):
    print('Running B', x, y)

# Example
a = TaggedActor()
a.start()
a.send(('A', 1))   # Invokes do_A(1)
a.send(('B', 2, 3))  # Invokes do_B(2,3)
a.close()
a.join()

from threading import Event
class Result:
  def __init__(self):
    self._evt = Event()
    self._result = None

  def set_result(self, value):
    self._result = value

    self._evt.set()

  def result(self):
    self._evt.wait()
    return self._result

class Worker(Actor):
  def submit(self, func, *args, **kwargs):
    r = Result()
    self.send((func, args, kwargs, r))
    return r

  def run(self):
    while True:
      func, args, kwargs, r = self.recv()
      r.set_result(func(*args, **kwargs))

# Example use
worker = Worker()
worker.start()
r = worker.submit(pow, 2, 3)
worker.close()
worker.join()
print(r.result())