+def fib(n):
+ """Calculate n-th Fibonacci number. Very inefficiently."""
+ if n in (1, 2):
+ return 1
+ else:
+ return fib(n-1) + fib(n-2)
+
+
+class CommandHandler:
+
+ def __init__(self, world, queues_out):
+ self.world = world
+ self.queues_out = queues_out
+
+ def send_to(self, connection_id, msg):
+ """Send msg to client of connection_id."""
+ self.queues_out[connection_id].put(msg)
+
+ def send_all(self, msg):
+ """Send msg to all clients."""
+ for connection_id in self.queues_out:
+ self.send_to(connection_id, msg)
+
+ def cmd_fib(self, tokens, connection_id):
+ """Reply with n-th Fibonacci numbers, n taken from tokens[1:].
+
+ Numbers are calculated in parallel as far as possible, using fib().
+ A 'CALCULATING …' message is sent to caller before the result.
+ """
+ from multiprocessing import Pool
+ fib_fail = 'MALFORMED FIB REQUEST'
+ if len(tokens) < 2:
+ self.send_to(connection_id, fib_fail)
+ return
+ numbers = []
+ for token in tokens[1:]:
+ if token != '0' and token.isdigit():
+ numbers += [int(token)]
+ else:
+ self.send_to(connection_id, fib_fail)
+ return
+ self.send_to(connection_id, 'CALCULATING …')
+ with Pool(len(numbers)) as p:
+ results = p.map(fib, numbers)
+ reply = ' '.join([str(r) for r in results])
+ self.send_to(connection_id, reply)
+
+ def cmd_inc(self, connection_id):
+ """Increment world.turn, send TURN_FINISHED, NEW_TURN to everyone."""
+ self.send_all('TURN_FINISHED ' + str(self.world.turn))
+ self.world.turn += 1
+ self.send_all('NEW_TURN ' + str(self.world.turn))
+
+ def cmd_get_turn(self, connection_id):
+ """Send world.turn to caller."""
+ self.send_to(connection_id, str(self.world.turn))
+
+ def cmd_echo(self, tokens, input_, connection_id):
+ """Send message in input_ beyond tokens[0] to caller."""
+ msg = input_[len(tokens[0]) + 1:]
+ self.send_to(connection_id, msg)
+
+ def cmd_all(self, tokens, input_):
+ """Send message in input_ beyond tokens[0] to all clients."""
+ msg = input_[len(tokens[0]) + 1:]
+ self.send_all(msg)
+
+ def handle_input(self, input_, connection_id):
+ """Process input_ to command grammar, call command handler if found."""
+ tokens = [token for token in input_.split(' ') if len(token) > 0]
+ if len(tokens) == 0:
+ self.send_to(connection_id, 'EMPTY COMMAND')
+ elif len(tokens) == 1 and tokens[0] == 'INC':
+ self.cmd_inc(connection_id)
+ elif len(tokens) == 1 and tokens[0] == 'GET_TURN':
+ self.cmd_get_turn(connection_id)
+ elif len(tokens) >= 1 and tokens[0] == 'ECHO':
+ self.cmd_echo(tokens, input_, connection_id)
+ elif len(tokens) >= 1 and tokens[0] == 'ALL':
+ self.cmd_all(tokens, input_)
+ elif len(tokens) >= 1 and tokens[0] == 'FIB':
+ # TODO: Should this really block the whole loop?
+ self.cmd_fib(tokens, connection_id)
+ else:
+ self.send_to(connection_id, 'UNKNOWN COMMAND')
+
+
+def io_loop(q):
+ """Handle commands coming through queue q, send results back.
+
+ Commands from q are expected to be tuples, with the first element either
+ 'ADD_QUEUE', 'COMMAND', or 'KILL_QUEUE', the second element a UUID, and
+ an optional third element of arbitrary type. The UUID identifies a
+ receiver for replies.
+
+ An 'ADD_QUEUE' command should contain as third element a queue through
+ which to send messages back to the sender of the command. A 'KILL_QUEUE'
+ command removes the queue for that receiver from the list of queues through
+ which to send replies.
+
+ A 'COMMAND' command is specified in greater detail by a string that is the
+ tuple's third element. CommandHandler takes care of processing this and
+ sending out replies.
+ """
+ queues_out = {}
+ world = World()
+ command_handler = CommandHandler(world, queues_out)
+ while True:
+ x = q.get()
+ command_type = x[0]
+ connection_id = x[1]
+ content = None if len(x) == 2 else x[2]
+ if command_type == 'ADD_QUEUE':
+ queues_out[connection_id] = content
+ elif command_type == 'COMMAND':
+ command_handler.handle_input(content, connection_id)
+ elif command_type == 'KILL_QUEUE':
+ del queues_out[connection_id]
+
+
+q = queue.Queue()
+c = threading.Thread(target=io_loop, daemon=True, args=(q,))
+c.start()
+server = Server(q, ('localhost', 5000), IO_Handler)