import zmq
import socket
import sys

class ZMQBase:
    def __init__(self, host='127.0.0.1',port = 5678):

        self.host=host
        self.port = port
        self.msg={'action':'','PV':'','host':'','pid':0}

        self.REQUEST_TIMEOUT = 500
        self.REQUEST_RETRIES = 2
        self.SERVER_ENDPOINT = "tcp://%s:%d" % (host,port)
        self.serverIsOffline=False    # assume that it is online

    def ZMQServerInfo(self,PVroot,host,pid):
        self.msg['PV']=PVroot
        self.msg['host']=host
        self.msg['pid']=pid


    def ZMQPoll(self,tag='ping'):
        self.msg['action']=tag
        context = zmq.Context()
        client = context.socket(zmq.REQ)
        client.connect(self.SERVER_ENDPOINT)
        client.send_pyobj(self.msg)

        retries_left = self.REQUEST_RETRIES
        while True:
            if (client.poll(self.REQUEST_TIMEOUT) & zmq.POLLIN) != 0:
                reply = client.recv_pyobj()
                check = self.ZMQIdentifyReply(reply)
                if self.serverIsOffline:
                    self.logger.info("Watchdog server came online")
                self.serverIsOffline=False
                if check:
                    if reply['action'] == 'quit':
                        client.close()
                        context.term()
                    return (reply['action'] == 'quit')
                else:
                    self.logger.warning("Malformed reply from server")
                    continue

            retries_left -= 1
            # Socket is confused. Close and remove it.
            client.setsockopt(zmq.LINGER, 0)
            client.close()
            if retries_left == 0:
                if not self.serverIsOffline:
                    self.logger.info("Watchdog server seems to be offline")
                    self.serverIsOffline=True
                context.term()
                return False

            # Create new connection
            client = context.socket(zmq.REQ)
            client.connect(self.SERVER_ENDPOINT)
            client.send_pyobj(self.msg)


    def ZMQIdentifyReply(self,reply):
        for field in ['PV','host','pid']:
            if not reply[field] == self.msg[field]:
                return False
        return True