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) 2008-2018 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  #
# Software Foundation; version 2 of the License.                              #
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# This program is distributed in the hope that it will be useful, but WITHOUT #
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# You should have received a copy of the GNU General Public License along     #
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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 json
import logging
import time

import websockets

from openlp.core.common.mixins import LogMixin, RegistryProperties
from openlp.core.common.registry import Registry
from openlp.core.common.settings import Settings
from openlp.core.threading import ThreadWorker, run_thread

log = logging.getLogger(__name__)


class WebSocketWorker(ThreadWorker):
    """
    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().__init__()

    def start(self):
        """
        Run the worker.
        """
        self.ws_server.start_server()
        self.quit.emit()

    def stop(self):
        """
        Stop the websocket server
        """
        self.ws_server.stop_server()


class WebSocketServer(RegistryProperties, LogMixin):
    """
    Wrapper round a server instance
    """
    def __init__(self):
        """
        Initialise and start the WebSockets server
        """
        super(WebSocketServer, self).__init__()
        if Registry().get_flag('no_web_server'):
            self.settings_section = 'api'
            worker = WebSocketWorker(self)
            run_thread(worker, 'websocket_server')

    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 stop_server(self):
        """
        Stop the websocket server
        """
        if hasattr(self.ws_server, 'ws_server'):
            self.ws_server.ws_server.close()
        elif hasattr(self.ws_server, 'server'):
            self.ws_server.server.close()

    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
    async 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:
                    await request.send(json.dumps(current_poll).encode())
                    previous_poll = current_poll
                await asyncio.sleep(0.2)
        elif path == '/live_changed':
            while True:
                main_poll = poller.main_poll()
                if main_poll != previous_main_poll:
                    await request.send(main_poll)
                    previous_main_poll = main_poll
                await asyncio.sleep(0.2)