import json

from messaging import Messaging


class EventHandlerBase:
    def __init__(self, anchor):
        self.messaging = Messaging()
        self.anchor = anchor
        self.subscriptions = set()
        self.subscribe(self.anchor)
        self.subscribe('reset')
        self.messaging.register_callback(self.event_handler_callback)

    def event_handler_callback(self, msg_parts):
        anchor, message = msg_parts
        data_json = json.loads(message)
        response = self.handle_event(anchor, data_json) if anchor != b'reset' else self.handle_reset(data_json)
        if response is None: return
        encoded_response = json.dumps(response).encode('utf-8')
        self.messaging.send(anchor, encoded_response)

    def handle_event(self, anchor, data_json):
        raise NotImplementedError

    def handle_reset(self, data_json):
        return None

    def message_other(self, anchor, data):
        encoded_anchor = anchor.encode('utf-8')
        message = {
            'anchor': anchor,
            'data': data
        }
        encoded_message = json.dumps(message).encode('utf-8')
        self.messaging.send(encoded_anchor, encoded_message)

    def subscribe(self, anchor):
        if anchor not in self.subscriptions:
            self.subscriptions.add(anchor)
            self.messaging.subscribe(anchor)

    def unsubscribe(self, anchor):
        try:
            self.subscriptions.remove(anchor)
            self.messaging.unsubscribe(anchor)
        except KeyError:
            pass

    def unsubscribe_all(self):
        for sub in self.subscriptions:
            self.messaging.unsubscribe(anchor=sub)
        self.subscriptions.clear()