from time import sleep
from bsread import source
from bsvar import BSVar
from prodthread import ProdThread


class BSCache:

    def __init__(self):
        self.channels = set()
        self.data = None
        self.pt = ProdThread(self.run)


    def __iter__(self):
        return self

    def __next__(self):
        self.pt.start()
        self.data = data = self.pt.queue.get()
        return data


    def run(self, queue, running):
        channels = self.channels
        with source(channels=channels, receive_timeout=-1) as src:
            while running.is_set():
                msg = src.receive()
                data = repack(channels, msg)
                if data:
                    queue.put(data)


    def stop(self, *args):
        print("\n\nstopping\n\n", args)
        self.pt.stop()


    def get_var(self, name):
        if name is not "pid" and not name in self.channels:
            self.update_source(name)
        return BSVar(name, self)


    def update_source(self, name):
        self.pt.stop()
        print("add channel", name)
        self.channels.add(name)
        self.pt.start()





def repack(channels, message):
    data     = message.data.data
    pulse_id = message.data.pulse_id

    res = {n: data[n].value for n in channels}
#    res = {k: v for k, v in res.items() if v is not None}

    #TODO: should this be a ValueError?
    if any(v is None for v in res.values()):
        return None

    if not res:
        return None

    res["pid"] = pulse_id
    return res