import select

from lcm import LCM


class Subscriber():
    def __init__(self, channel_list, msg_handler):
        self._lcm = LCM()
        self._subscription_list = []
        for channel in channel_list:
            self._subscription_list.append(self._lcm.subscribe(channel, msg_handler))

        self._fd = self._lcm.fileno()
        
    def __enter__(self):
        return self


    def __exit__(self, type, value, traceback):
        self.close()
        

    def get(self):
        (fd_list,dum,dum) = select.select([self._fd],[],[],0)
        if fd_list:
            self._lcm.handle()
            return True
        else:
            return False


    def close(self):
        for sub in self._subscription_list:
            self._lcm.unsubscribe(sub)


class Publisher():
    def __init__(self):
        self._lcm = LCM()

    
    def __enter__(self):
        return self


    def __exit__(self, type, value, traceback):
        pass


    def publish(self, channel, msg):
        self._lcm.publish(channel, msg.encode())