import json
import sys


def print_msg_diff(filename, actor_id, msg_number):
    def get_diff(msg):
        send_ts = msg['send_ts']
        recv_ts = msg['recv_ts']

        if send_ts == -1 or recv_ts == -1:
            return None

        return recv_ts - send_ts

    with open(filename) as f:
        msg_intervals = json.load(f)

    actor = msg_intervals[actor_id]

    if msg_number is None:
        for msg_number in sorted(actor.keys()):
            msg = actor[msg_number]
            print('{}: {}'.format(msg_number, get_diff(msg)))
    else:
        print(get_diff(actor[msg_number]))


if __name__ == '__main__':
    filename = sys.argv[1]
    actor_id = sys.argv[2]
    msg_number = None

    if len(sys.argv) > 3:
        msg_number = sys.argv[3]

    print_msg_diff(filename, actor_id, msg_number)