openlp/openlp/core/api/websockets.py

# -*- coding: utf-8 -*-
# vim: autoindent shiftwidth=4 expandtab textwidth=120 tabstop=4 softtabstop=4

###############################################################################
# OpenLP - Open Source Lyrics Projection                                      #
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# Copyright (c) 2008-2016 OpenLP Developers                                   #
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# This program is free software; you can redistribute it and/or modify it     #
# under the terms of the GNU General Public License as published by the Free  #
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"""
The :mod:`http` module contains the API web server. This is a lightweight web server used by remotes to interact
with OpenLP. It uses JSON to communicate with the remotes.
"""

import asyncio
import websockets
import logging
import time

from PyQt5 import QtCore

from openlp.core.common import Settings, RegistryProperties, OpenLPMixin, Registry

log = logging.getLogger(__name__)


class WebSocketWorker(QtCore.QObject):
    """
    A special Qt thread class to allow the WebSockets server to run at the same time as the UI.
    """
    def __init__(self, server):
        """
        Constructor for the thread class.

        :param server: The http server class.
        """
        self.ws_server = server
        super(WebSocketWorker, self).__init__()

    def run(self):
        """
        Run the thread.
        """
        self.ws_server.start_server()

    def stop(self):
        self.ws_server.stop = True


class WebSocketServer(RegistryProperties, OpenLPMixin):
    """
    Wrapper round a server instance
    """
    def __init__(self):
        """
        Initialise and start the WebSockets server
        """
        super(WebSocketServer, self).__init__()
        self.settings_section = 'api'
        self.worker = WebSocketWorker(self)
        self.thread = QtCore.QThread()
        self.worker.moveToThread(self.thread)
        self.thread.started.connect(self.worker.run)
        self.thread.start()

    def start_server(self):
        """
        Start the correct server and save the handler
        """
        address = Settings().value(self.settings_section + '/ip address')
        port = Settings().value(self.settings_section + '/websocket port')
        self.start_websocket_instance(address, port)
        # If web socket server start listening
        if hasattr(self, 'ws_server') and self.ws_server:
            event_loop = asyncio.new_event_loop()
            asyncio.set_event_loop(event_loop)
            event_loop.run_until_complete(self.ws_server)
            event_loop.run_forever()
        else:
            log.debug('Failed to start ws server on port {port}'.format(port=port))

    def start_websocket_instance(self, address, port):
        """
        Start the server

        :param address: The server address
        :param port: The run port
        """
        loop = 1
        while loop < 4:
            try:
                self.ws_server = websockets.serve(self.handle_websocket, address, port)
                log.debug("Web Socket Server started for class {address} {port}".format(address=address, port=port))
                break
            except Exception as e:
                log.error('Failed to start ws server {why}'.format(why=e))
                loop += 1
                time.sleep(0.1)

    @staticmethod
    @asyncio.coroutine
    def handle_websocket(request, path):
        """
        Handle web socket requests and return the poll information.
        Check ever 0.2 seconds to get the latest position and send if changed.
        Only gets triggered when 1st client attaches

        :param request: request from client
        :param path: determines the endpoints supported
        :return:
        """
        log.debug("web socket handler registered with client")
        previous_poll = None
        previous_main_poll = None
        poller = Registry().get('poller')
        if path == '/state':
            while True:
                current_poll = poller.poll()
                if current_poll != previous_poll:
                    yield from request.send(current_poll)
                    previous_poll = current_poll
                yield from asyncio.sleep(0.2)
        elif path == '/live_changed':
            while True:
                main_poll = poller.main_poll()
                if main_poll != previous_main_poll:
                    yield from request.send(main_poll)
                    previous_main_poll = main_poll
                yield from asyncio.sleep(0.2)