counter.py - mozsearch

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#!/usr/bin/env python

import asyncio

import json

import logging

import websockets

logging.basicConfig()

USERS = set()

VALUE = 0

def users_event():

    return json.dumps({"type": "users", "count": len(USERS)})

def value_event():

    return json.dumps({"type": "value", "value": VALUE})

async def counter(websocket):

    global USERS, VALUE

    try:

        # Register user

        USERS.add(websocket)

        websockets.broadcast(USERS, users_event())

        # Send current state to user

        await websocket.send(value_event())

        # Manage state changes

        async for message in websocket:

            event = json.loads(message)

            if event["action"] == "minus":

                VALUE -= 1

                websockets.broadcast(USERS, value_event())

            elif event["action"] == "plus":

                VALUE += 1

                websockets.broadcast(USERS, value_event())

            else:

                logging.error("unsupported event: %s", event)

    finally:

        # Unregister user

        USERS.remove(websocket)

        websockets.broadcast(USERS, users_event())

async def main():

    async with websockets.serve(counter, "localhost", 6789):

        await asyncio.Future()  # run forever

if __name__ == "__main__":

    asyncio.run(main())