#!/usr/bin/python
# -*- coding: utf-8 -*-
"""
   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
"""
import logging
try:
    from http.server import HTTPServer, BaseHTTPRequestHandler
except ImportError:
    from BaseHTTPServer import HTTPServer, BaseHTTPRequestHandler
try:
    import socketserver
except ImportError:
    import SocketServer as socketserver
import socket
import ssl

import mimetypes
import webbrowser
import struct
import socket
import base64
import hashlib
import sys
import threading
import signal
import time
import os
import re
try:
    from urllib import unquote
    from urllib import quote
    from urlparse import urlparse
    from urlparse import parse_qs
except ImportError:
    from urllib.parse import unquote
    from urllib.parse import quote
    from urllib.parse import unquote_to_bytes
    from urllib.parse import urlparse
    from urllib.parse import parse_qs
import cgi
import weakref


clients = {}
runtimeInstances = weakref.WeakValueDictionary()

pyLessThan3 = sys.version_info < (3,)


_MSG_ACK = '3'
_MSG_JS = '2'
_MSG_UPDATE = '1'


def to_websocket(data):
    # encoding end decoding utility function
    if pyLessThan3:
        return quote(data)
    return quote(data, encoding='utf-8')


def from_websocket(data):
    # encoding end decoding utility function
    if pyLessThan3:
        return unquote(data)
    return unquote(data, encoding='utf-8')


def encode_text(data):
    if not pyLessThan3:
        return data.encode('utf-8')
    return data


def get_method_by_name(root_node, name):
    val = None
    if hasattr(root_node, name):
        val = getattr(root_node, name)
    return val


def get_method_by_id(_id):
    global runtimeInstances
    return runtimeInstances.get(str(_id), None)


def parse_session_cookie(cookie_to_cook):
    """ cookie_to_cook = http_header['cookie']
    """
    #print("cookie_to_cook: %s"%str(cookie_to_cook))
    session_value = None
    tokens = cookie_to_cook.split(";")
    for tok in tokens:
        if 'remi_session=' in tok:
            #print("found session id: %s"%str(tok))
            try:
                session_value = int(tok.replace('remi_session=', ''))
            except:
                pass
    return session_value


class WebSocketsHandler(socketserver.StreamRequestHandler):

    magic = b'258EAFA5-E914-47DA-95CA-C5AB0DC85B11'

    def __init__(self, headers, *args, **kwargs):
        self.headers = headers
        self.handshake_done = False
        self._log = logging.getLogger('smarthome.server.ws')
        socketserver.StreamRequestHandler.__init__(self, *args, **kwargs)

    def setup(self):
        socketserver.StreamRequestHandler.setup(self)
        self._log.info('connection established: %r' % (self.client_address,))
        self.handshake_done = False

    def handle(self):
        global clients
        self._log.debug('handle')
        # on some systems like ROS, the default socket timeout
        # is less than expected, we force it to infinite (None) as default socket value
        self.request.settimeout(None)
        if self.handshake():
            while True:
                if not self.read_next_message():
                    clients[self.session].websockets.remove(self)
                    self.handshake_done = False
                    self._log.debug('ws ending websocket service')
                    break

    @staticmethod
    def bytetonum(b):
        if pyLessThan3:
            b = ord(b)
        return b

    def read_next_message(self):
        # noinspection PyBroadException
        try:
            try:
                length = self.rfile.read(2)
            except ValueError:
                # socket was closed, just return without errors
                return False
            length = self.bytetonum(length[1]) & 127
            if length == 126:
                length = struct.unpack('>H', self.rfile.read(2))[0]
            elif length == 127:
                length = struct.unpack('>Q', self.rfile.read(8))[0]
            masks = [self.bytetonum(byte) for byte in self.rfile.read(4)]
            decoded = ''
            for char in self.rfile.read(length):
                decoded += chr(self.bytetonum(char) ^ masks[len(decoded) % 4])
            self.on_message(from_websocket(decoded))
        except socket.timeout:
            return False
        except Exception:
            return False
        return True

    def send_message(self, message):
        if not self.handshake_done:
            self._log.warning("ignoring message %s (handshake not done)" % message[:10])
            return

        self._log.debug('send_message: %s... -> %s' % (message[:10], self.client_address))
        out = bytearray()
        out.append(129)
        length = len(message)
        if length <= 125:
            out.append(length)
        elif 126 <= length <= 65535:
            out.append(126)
            out += struct.pack('>H', length)
        else:
            out.append(127)
            out += struct.pack('>Q', length)
        if not pyLessThan3:
            message = message.encode('utf-8')
        out = out + message
        self.request.send(out)

    def handshake(self):
        self._log.debug('handshake')
        key = self.headers['Sec-WebSocket-Key']
        self.session = None
        if 'cookie' in self.headers:
            if self.headers['cookie']!=None:
                self.session = parse_session_cookie(self.headers['cookie'])
        if self.session == None:
            return False
        if not self.session in clients.keys():
            return False

        digest = hashlib.sha1((key.encode("utf-8")+self.magic))
        digest = digest.digest()
        digest = base64.b64encode(digest)
        response = 'HTTP/1.1 101 Switching Protocols\r\n'
        response += 'Upgrade: websocket\r\n'
        response += 'Connection: Upgrade\r\n'
        response += 'Sec-WebSocket-Accept: %s\r\n\r\n' % digest.decode("utf-8")
        self._log.info('handshake complete')
        self.request.sendall(response.encode("utf-8"))
        self.handshake_done = True

        #if an update happens since the websocket connection to its handshake,
        # it gets not displayed. it is required to inform App about handshake done,
        # to get a full refresh
        clients[self.session].websocket_handshake_done(self)

        return True

    def on_message(self, message):
        global runtimeInstances

        self.send_message(_MSG_ACK)

        with clients[self.session].update_lock:
            # noinspection PyBroadException
            try:
                # saving the websocket in order to update the client
                if self not in clients[self.session].websockets:
                    clients[self.session].websockets.append(self)

                # parsing messages
                chunks = message.split('/')
                self._log.debug('on_message: %s' % chunks[0])

                if len(chunks) > 3:  # msgtype,widget,function,params
                    # if this is a callback
                    msg_type = 'callback'
                    if chunks[0] == msg_type:
                        widget_id = chunks[1]
                        function_name = chunks[2]
                        params = message[
                            len(msg_type) + len(widget_id) + len(function_name) + 3:]

                        param_dict = parse_parametrs(params)

                        callback = get_method_by_name(runtimeInstances[widget_id], function_name)
                        if callback is not None:
                            callback(**param_dict)

            except Exception:
                self._log.error('error parsing websocket', exc_info=True)

    def close(self, terminate_server=True):
        try:
            self.request.shutdown(socket.SHUT_WR)
            self.finish()
            if terminate_server:
                self.server.shutdown()
        except:
            self._log.error("exception in WebSocketsHandler.close method", exc_info=True)


def parse_parametrs(p):
    """
    Parses the parameters given from POST or websocket reqs
    expecting the parameters as:  "11|par1='asd'|6|par2=1"
    returns a dict like {par1:'asd',par2:1}
    """
    ret = {}
    while len(p) > 1 and p.count('|') > 0:
        s = p.split('|')
        l = int(s[0])  # length of param field
        if l > 0:
            p = p[len(s[0]) + 1:]
            field_name = p.split('|')[0].split('=')[0]
            field_value = p[len(field_name) + 1:l]
            p = p[l + 1:]
            ret[field_name] = field_value
    return ret


# noinspection PyPep8Naming
class App(BaseHTTPRequestHandler, object):

    """
    This class will handles any incoming request from the browser
    The main application class can subclass this
    In the do_POST and do_GET methods it is expected to receive requests such as:
        - function calls with parameters
        - file requests
    """

    re_static_file = re.compile(r"^([\/]*[\w\d]+:[-_. $@?#£'%=()\/\[\]!+°§^,\w\d]+)") #https://regex101.com/r/uK1sX1/6
    re_attr_call = re.compile(r"^/*(\w+)\/(\w+)\?{0,1}(\w*\={1}(\w|\.)+\&{0,1})*$")

    def __init__(self, request, client_address, server, **app_args):
        self._app_args = app_args
        self.root = None
        self._log = logging.getLogger('smarthome.request  ')
        super(App, self).__init__(request, client_address, server)

    def _get_list_from_app_args(self, name):
        try:
            v = self._app_args[name]
            if isinstance(v, (tuple, list)):
                vals = v
            else:
                vals = [v]
        except KeyError:
            vals = []
        return vals

    def _instance(self):
        global clients
        global runtimeInstances
        """
        This method is used to get the Application instance previously created
        managing on this, it is possible to switch to "single instance for
        multiple clients" or "multiple instance for multiple clients" execution way
        """

        self.session = 0
        #checking previously defined session
        if 'cookie' in self.headers:
            self.session = parse_session_cookie(self.headers['cookie'])
            #if not a valid session id
            if self.session == None:
                self.session = 0
            if not self.session in clients.keys():
                self.session = 0

        #if no session id
        if self.session == 0:
            if self.server.multiple_instance:
                self.session = int(time.time()*1000)
            #send session to browser
            del self.headers['cookie']

        #if the client instance doesn't exist
        if not(self.session in clients):
            self.update_interval = self.server.update_interval

            from remi import gui

            head = gui.HEAD(self.server.title)
            # use the default css, but append a version based on its hash, to stop browser caching
            head.add_child('internal_css', "<link href='/res:style.css' rel='stylesheet' />\n")

            body = gui.BODY()
            body.onload.connect(self.onload)
            body.onerror.connect(self.onerror)
            body.ononline.connect(self.ononline)
            body.onpagehide.connect(self.onpagehide)
            body.onpageshow.connect(self.onpageshow)
            body.onresize.connect(self.onresize)
            self.page = gui.HTML()
            self.page.add_child('head', head)
            self.page.add_child('body', body)

            if not hasattr(self, 'websockets'):
                self.websockets = []

            self.update_lock = threading.RLock()

            if not hasattr(self, '_need_update_flag'):
                self._need_update_flag = False
                self._stop_update_flag = False
                if self.update_interval > 0:
                    self._update_thread = threading.Thread(target=self._idle_loop)
                    self._update_thread.setDaemon(True)
                    self._update_thread.start()

            runtimeInstances[str(id(self))] = self
            clients[self.session] = self
        else:
            #restore instance attributes
            client = clients[self.session]

            self.websockets = client.websockets
            self.page = client.page

            self.update_lock = client.update_lock

            self.update_interval = client.update_interval
            self._need_update_flag = client._need_update_flag
            if hasattr(client, '_update_thread'):
                self._update_thread = client._update_thread

        net_interface_ip = self.headers.get('Host', "%s:%s"%(self.connection.getsockname()[0],self.server.server_address[1]))
        websocket_timeout_timer_ms = str(self.server.websocket_timeout_timer_ms)
        pending_messages_queue_length = str(self.server.pending_messages_queue_length)
        self.page.children['head'].set_internal_js(net_interface_ip, pending_messages_queue_length, websocket_timeout_timer_ms)

    def main(self, *_):
        """ Subclasses of App class *must* declare a main function
            that will be the entry point of the application.
            Inside the main function you have to declare the GUI structure
            and return the root widget. """
        raise NotImplementedError("Applications must implement 'main()' function.")

    def _idle_loop(self):
        """ This is used to exec the idle function in a safe context and a separate thread
        """
        while not self._stop_update_flag:
            time.sleep(self.update_interval)
            with self.update_lock:
                try:
                    self.idle()
                except:
                    self._log.error("exception in App.idle method", exc_info=True)
                if self._need_update_flag:
                    try:
                        self.do_gui_update()
                    except:
                        self._log.error('''exception during gui update. It is advisable to
                            use App.update_lock using external threads.''', exc_info=True)

    def idle(self):
        """ Idle function called every UPDATE_INTERVAL before the gui update.
            Useful to schedule tasks. """
        pass

    def _need_update(self, emitter=None):
        if self.update_interval == 0:
            #no interval, immadiate update
            self.do_gui_update()
        else:
            #will be updated after idle loop
            self._need_update_flag = True

    def do_gui_update(self):
        """ This method gets called also by Timer, a new thread, and so needs to lock the update
        """
        with self.update_lock:
            changed_widget_dict = {}
            self.root.repr(changed_widget_dict)
            for widget in changed_widget_dict.keys():
                html = changed_widget_dict[widget]
                __id = str(widget.identifier)
                self._send_spontaneous_websocket_message(_MSG_UPDATE + __id + ',' + to_websocket(html))
        self._need_update_flag = False

    def websocket_handshake_done(self, ws_instance_to_update):
        with self.update_lock:
            msg = "0" + self.root.identifier + ',' + to_websocket(self.page.children['body'].innerHTML({}))
        ws_instance_to_update.send_message(msg)

    def set_root_widget(self, widget):
        self.page.children['body'].append(widget, 'root')
        self.root = widget
        self.root.disable_refresh()
        self.root.attributes['data-parent-widget'] = str(id(self))
        self.root._parent = self
        self.root.enable_refresh()

        msg = "0" + self.root.identifier + ',' + to_websocket(self.page.children['body'].innerHTML({}))
        self._send_spontaneous_websocket_message(msg)

    def _send_spontaneous_websocket_message(self, message):
        for ws in self.websockets[:]:
            # noinspection PyBroadException
            try:
                #self._log.debug("sending websocket spontaneous message")
                ws.send_message(message)
            except:
                self._log.error("sending websocket spontaneous message", exc_info=True)
                try:
                    self.websockets.remove(ws)
                    ws.close(terminate_server=False)
                except:
                    self._log.error("unable to remove websocket client - already not in list", exc_info=True)

    def execute_javascript(self, code):
        self._send_spontaneous_websocket_message(_MSG_JS + code)

    def notification_message(self, title, content, icon=""):
        """This function sends "javascript" message to the client, that executes its content.
           In this particular code, a notification message is shown
        """
        code = """
            var options = {
                body: "%(content)s",
                icon: "%(icon)s"
            }
            if (!("Notification" in window)) {
                alert("%(content)s");
            }else if (Notification.permission === "granted") {
                var notification = new Notification("%(title)s", options);
            }else if (Notification.permission !== 'denied') {
                Notification.requestPermission(function (permission) {
                    if (permission === "granted") {
                        var notification = new Notification("%(title)s", options);
                    }
                });
            }
        """ % {'title': title, 'content': content, 'icon': icon}
        self.execute_javascript(code)

    def do_POST(self):
        self._instance()
        file_data = None
        # listener_widget = None
        # listener_function = None
        try:
            # Parse the form data posted
            filename = self.headers['filename']
            listener_widget = runtimeInstances[self.headers['listener']]
            listener_function = self.headers['listener_function']
            form = cgi.FieldStorage(fp=self.rfile,
                                    headers=self.headers,
                                    environ={'REQUEST_METHOD': 'POST',
                                             'CONTENT_TYPE': self.headers['Content-Type']})
            # Echo back information about what was posted in the form
            for field in form.keys():
                field_item = form[field]
                if field_item.filename:
                    # The field contains an uploaded file
                    file_data = field_item.file.read()
                    file_len = len(file_data)
                    self._log.debug('post: uploaded %s as "%s" (%d bytes)\n' % (field, field_item.filename, file_len))
                    get_method_by_name(listener_widget, listener_function)(file_data, filename)
                else:
                    # Regular form value
                    self._log.debug('post: %s=%s\n' % (field, form[field].value))

            if file_data is not None:
                # the filedata is sent to the listener
                self._log.debug('GUI - server.py do_POST: fileupload name= %s' % (filename))
                self.send_response(200)
        except Exception:
            self._log.error('post: failed', exc_info=True)
            self.send_response(400)
        self.send_header('Content-type', 'text/plain')
        self.end_headers()

    def do_HEAD(self):
        self.send_response(200)
        self.end_headers()

    def do_AUTHHEAD(self):
        self.send_response(401)
        self.send_header('WWW-Authenticate', 'Basic realm=\"Protected\"')
        self.send_header('Content-type', 'text/html')
        self.end_headers()

    def do_GET(self):
        # check here request header to identify the type of req, if http or ws
        # if this is a ws req, instance a ws handler, add it to App's ws list, return
        if "Upgrade" in self.headers:
            if self.headers['Upgrade'] == 'websocket':
                #passing arguments to websocket handler, otherwise it will lost the last message,
                # and will be unable to handshake
                ws = WebSocketsHandler(self.headers, self.request, self.client_address, self.server)
                return

        """Handler for the GET requests."""
        do_process = False
        if self.server.auth is None:
            do_process = True
        else:
            if not ('Authorization' in self.headers) or self.headers['Authorization'] is None:
                self._log.info("Authenticating")
                self.do_AUTHHEAD()
                self.wfile.write(encode_text('no auth header received'))
            elif self.headers['Authorization'] == 'Basic ' + self.server.auth.decode():
                do_process = True
            else:
                self.do_AUTHHEAD()
                self.wfile.write(encode_text(self.headers['Authorization']))
                self.wfile.write(encode_text('not authenticated'))

        if do_process:
            path = str(unquote(self.path))
            # noinspection PyBroadException
            try:
                self._instance()
                # build the page (call main()) in user code, if not built yet
                with self.update_lock:
                    # build the root page once if necessary
                    if not 'root' in self.page.children['body'].children.keys():
                        self._log.info('built UI (path=%s)' % path)
                        self.set_root_widget(self.main(*self.server.userdata))
                self._process_all(path)
            except:
                self._log.error('error processing GET request', exc_info=True)

    def _get_static_file(self, filename):
        filename = filename.replace("..", "") #avoid backdirs
        __i = filename.find(':')
        if __i < 0:
            return None
        key = filename[:__i]
        path = filename[__i+1:]
        key = key.replace("/","")
        paths = {'res': os.path.join(os.path.dirname(__file__), "res")}
        static_paths = self._app_args.get('static_file_path', {})
        if not type(static_paths)==dict:
            self._log.error("App's parameter static_file_path must be a Dictionary.", exc_info=False)
            static_paths = {}
        paths.update(static_paths)
        if not key in paths:
            return None
        return os.path.join(paths[key], path)

    def _process_all(self, func):
        self._log.debug('get: %s' % func)

        static_file = self.re_static_file.match(func)
        attr_call = self.re_attr_call.match(func)

        if (func == '/') or (not func):
            self.send_response(200)
            self.send_header("Set-Cookie", "remi_session=%s"%(self.session))
            self.send_header('Content-type', 'text/html')
            self.end_headers()

            with self.update_lock:
                # render the HTML
                page_content = self.page.repr()

            self.wfile.write(encode_text("<!DOCTYPE html>\n"))
            self.wfile.write(encode_text(page_content))

        elif static_file:
            filename = self._get_static_file(static_file.groups()[0])
            if not filename:
                self.send_response(404)
                return
            mimetype, encoding = mimetypes.guess_type(filename)
            self.send_response(200)
            self.send_header('Content-type', mimetype if mimetype else 'application/octet-stream')
            if self.server.enable_file_cache:
                self.send_header('Cache-Control', 'public, max-age=86400')
            self.end_headers()
            with open(filename, 'rb') as f:
                content = f.read()
                self.wfile.write(content)
        elif attr_call:
            with self.update_lock:
                param_dict = parse_qs(urlparse(func).query)
                # parse_qs returns patameters as list, here we take the first element
                for k in param_dict:
                    param_dict[k] = param_dict[k][0]

                widget, func = attr_call.group(1, 2)
                try:
                    content, headers = get_method_by_name(get_method_by_id(widget), func)(**param_dict)
                    if content is None:
                        self.send_response(503)
                        return
                    self.send_response(200)
                except IOError:
                    self._log.error('attr %s/%s call error' % (widget, func), exc_info=True)
                    self.send_response(404)
                    return
                except (TypeError, AttributeError):
                    self._log.error('attr %s/%s not available' % (widget, func))
                    self.send_response(503)
                    return

            for k in headers:
                self.send_header(k, headers[k])
            self.end_headers()
            try:
                self.wfile.write(content)
            except TypeError:
                self.wfile.write(encode_text(content))

    def close(self):
        """ Command to initiate an App to close
        """
        self._log.debug('shutting down...')
        self.server.server_starter_instance.stop()

    def on_close(self):
        """ Called by the server when the App have to be terminated
        """
        self._stop_update_flag = True
        for ws in self.websockets:
            ws.close()

    def onload(self, emitter):
        """ WebPage Event that occurs on webpage loaded
        """
        self._log.debug('App.onload event occurred')

    def onerror(self, emitter, message, source, lineno, colno):
        """ WebPage Event that occurs on webpage errors
        """
        self._log.debug("""App.onerror event occurred in webpage:
            \nMESSAGE:%s\nSOURCE:%s\nLINENO:%s\nCOLNO:%s\n"""%(message, source, lineno, colno))

    def ononline(self, emitter):
        """ WebPage Event that occurs on webpage goes online after a disconnection
        """
        self._log.debug('App.ononline event occurred')

    def onpagehide(self, emitter):
        """ WebPage Event that occurs on webpage when the user navigates away
        """
        self._log.debug('App.onpagehide event occurred')

    def onpageshow(self, emitter):
        """ WebPage Event that occurs on webpage gets shown
        """
        self._log.debug('App.onpageshow event occurred')

    def onresize(self, emitter, width, height):
        """ WebPage Event that occurs on webpage gets resized
        """
        self._log.debug('App.onresize event occurred. Width:%s Height:%s'%(width, height))


class ThreadedHTTPServer(socketserver.ThreadingMixIn, HTTPServer):

    daemon_threads = False

    # noinspection PyPep8Naming
    def __init__(self, server_address, RequestHandlerClass,
                 auth, multiple_instance, enable_file_cache, update_interval,
                 websocket_timeout_timer_ms, pending_messages_queue_length,
                 title, server_starter_instance, certfile, keyfile, ssl_version, *userdata):
        HTTPServer.__init__(self, server_address, RequestHandlerClass)
        self.auth = auth
        self.multiple_instance = multiple_instance
        self.enable_file_cache = enable_file_cache
        self.update_interval = update_interval
        self.websocket_timeout_timer_ms = websocket_timeout_timer_ms
        self.pending_messages_queue_length = pending_messages_queue_length
        self.title = title
        self.server_starter_instance = server_starter_instance
        self.userdata = userdata

        self.certfile = certfile
        self.keyfile = keyfile
        self.ssl_version = ssl_version
        if self.ssl_version!=None:
            self.socket = ssl.wrap_socket(self.socket, keyfile=self.keyfile, certfile=self.certfile, server_side=True, ssl_version=self.ssl_version, do_handshake_on_connect=True)


class Server(object):
    # noinspection PyShadowingNames
    def __init__(self, gui_class, title='', start=True, address='127.0.0.1', port=0, username=None, password=None,
                 multiple_instance=False, enable_file_cache=True, update_interval=0.1, start_browser=True,
                 websocket_timeout_timer_ms=1000, pending_messages_queue_length=1000,
                 certfile=None, keyfile=None, ssl_version=None,  userdata=()):

        self._gui = gui_class
        self._title = title or gui_class.__name__
        self._sserver = None
        self._sth = None
        self._base_address = ''
        self._address = address
        self._sport = port
        self._multiple_instance = multiple_instance
        self._enable_file_cache = enable_file_cache
        self._update_interval = update_interval
        self._start_browser = start_browser
        self._websocket_timeout_timer_ms = websocket_timeout_timer_ms
        self._pending_messages_queue_length = pending_messages_queue_length
        self._certfile = certfile
        self._keyfile = keyfile
        self._ssl_version = ssl_version
        self._userdata = userdata
        if username and password:
            self._auth = base64.b64encode(encode_text("%s:%s" % (username, password)))
        else:
            self._auth = None

        if not isinstance(userdata, tuple):
            raise ValueError('userdata must be a tuple')

        self._log = logging.getLogger('smarthome.server   ')
        self._alive = True
        if start:
            self._myid = threading.Thread.ident
            self.start()
            self.serve_forever()

    @property
    def title(self):
        return self._title

    @property
    def address(self):
        return self._base_address

    def start(self):
        # Create a web server and define the handler to manage the incoming
        # request
        self._sserver = ThreadedHTTPServer((self._address, self._sport), self._gui, self._auth,
                                           self._multiple_instance, self._enable_file_cache,
                                           self._update_interval, self._websocket_timeout_timer_ms,
                                           self._pending_messages_queue_length, self._title,
                                           self, self._certfile, self._keyfile, self._ssl_version, *self._userdata)
        shost, sport = self._sserver.socket.getsockname()[:2]
        self._log.info('Started httpserver http://%s:%s/'%(shost,sport))
        # when listening on multiple net interfaces the browsers connects to localhost
        if shost == '0.0.0.0':
            shost = '127.0.0.1'
        self._base_address = 'http://%s:%s/' % (shost,sport)
        if self._start_browser:
            try:
                import android
                android.webbrowser.open(self._base_address)
            except ImportError:
                # use default browser instead of always forcing IE on Windows
                if os.name == 'nt':
                    webbrowser.get('windows-default').open(self._base_address)
                else:
                    webbrowser.open(self._base_address)
        self._sth = threading.Thread(target=self._sserver.serve_forever)
        self._sth.daemon = False
        self._sth.start()

    def serve_forever(self):
        # we could join on the threads, but join blocks all interrupts (including
        # ctrl+c, so just spin here
        # noinspection PyBroadException
        try:
            def sig_manager(sig, callstack):
                self.stop()
                self._log.info('*** signal %d received.' % sig)
                return signal.SIG_IGN
            prev_handler = signal.signal(signal.SIGINT, sig_manager)
        except Exception:
            # signal.pause() is missing for Windows; wait 1ms and loop instead
            pass
        except KeyboardInterrupt:
            pass
        while self._alive:
            try:
                time.sleep(1)
            except:
                self._alive = False
        self._log.debug(' ** serve_forever() quitting')

    def stop(self):
        global clients
        self._alive = False
        self._sserver.shutdown()
        for client in clients.values():
            client.on_close()


class StandaloneServer(Server):
    def __init__(self, gui_class, title='', width=800, height=600, resizable=True, fullscreen=False, start=True,
                 userdata=()):
        Server.__init__(self, gui_class, title=title, start=False, address='127.0.0.1', port=0, username=None,
                        password=None,
                        multiple_instance=False, enable_file_cache=True, update_interval=0.1, start_browser=False,
                        websocket_timeout_timer_ms=1000, pending_messages_queue_length=1000, userdata=userdata)

        self._application_conf = {'width': width, 'height': height, 'resizable': resizable, 'fullscreen': fullscreen}

        if start:
            self.serve_forever()

    def serve_forever(self):
        try:
            import webview
        except ImportError:
            raise ImportError('PyWebView is missing. Please install it by:\n    '
                              'pip install pywebview\n    '
                              'more info at https://github.com/r0x0r/pywebview')
        else:
            Server.start(self)
            webview.create_window(self.title, self.address, **self._application_conf)
            webview.start()
            Server.stop(self)


def start(main_gui_class, **kwargs):
    """This method starts the webserver with a specific App subclass."""
    debug = kwargs.pop('debug', False)
    standalone = kwargs.pop('standalone', False)

    logging.basicConfig(level=logging.DEBUG if debug else logging.INFO,
                        format='%(name)-16s %(levelname)-8s %(message)s')
    logging.getLogger('remi').setLevel(
            level=logging.DEBUG if debug else logging.INFO)

    if standalone:
        s = StandaloneServer(main_gui_class, start=True, **kwargs)
    else:
        s = Server(main_gui_class, start=True, **kwargs)

