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# Source code for slixmpp.xmlstream.xmlstream

    # slixmpp.xmlstream.xmlstream
    # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    # This module provides the module for creating and
    # interacting with generic XML streams, along with
    # the necessary eventing infrastructure.
    # Part of Slixmpp: The Slick XMPP Library
    # :copyright: (c) 2011 Nathanael C. Fritz
    # :license: MIT, see LICENSE for more details
    from typing import (
        Any,
        Awaitable,
        Generator,
        Coroutine,
        Callable,
        Iterable,
        TypeVar,
        cast,
    )

    import asyncio
    import functools
    import logging
    import socket as Socket
    import ssl
    import uuid
    import warnings
    import weakref
    import collections

    from contextlib import contextmanager
    import xml.etree.ElementTree as ET
    from asyncio import (
        AbstractEventLoop,
        BaseTransport,
        Future,
        Task,
        TimerHandle,
        Transport,
        wait,
    )
    from inspect import iscoroutinefunction
    from pathlib import Path

    from slixmpp.types import FilterString
    from slixmpp.xmlstream.tostring import tostring
    from slixmpp.xmlstream.stanzabase import StanzaBase, ElementBase
    from slixmpp.xmlstream.resolver import resolve, default_resolver
    from slixmpp.xmlstream.handler.base import BaseHandler

    T = TypeVar('T')

    #: The time in seconds to wait before timing out waiting for response stanzas.
    RESPONSE_TIMEOUT = 30

    log = logging.getLogger(__name__)

    class ContinueQueue(Exception):
        """
        Exception raised in the send queue to "continue" from within an inner loop
        """

    class NotConnectedError(Exception):
        """
        Raised when we try to send something over the wire but we are not
        connected.
        """

    class InvalidCABundle(Exception):
        """
            Exception raised when the CA Bundle file hasn't been found.
        """

        def __init__(self, path: Path | Iterable[Path] | None):
            self.path = path

    _T = TypeVar('_T', str, ElementBase, StanzaBase)

    SyncFilter = Callable[[StanzaBase], StanzaBase | None]
    AsyncFilter = Callable[[StanzaBase], Awaitable[StanzaBase | None]]

    Filter = SyncFilter | AsyncFilter

    _FiltersDict = dict[str, list[Filter]]

    Handler = Callable[[Any], Any | Coroutine[Any, Any, Any]]

    class XMLStream(asyncio.BaseProtocol):
        """
        An XML stream connection manager and event dispatcher.

        The XMLStream class abstracts away the issues of establishing a
        connection with a server and sending and receiving XML "stanzas".
        A stanza is a complete XML element that is a direct child of a root
        document element. Two streams are used, one for each communication
        direction, over the same socket. Once the connection is closed, both
        streams should be complete and valid XML documents.

        Three types of events are provided to manage the stream:
            :Stream: Triggered based on received stanzas, similar in concept
                     to events in a SAX XML parser.
            :Custom: Triggered manually.
            :Scheduled: Triggered based on time delays.

        Typically, stanzas are first processed by a stream event handler which
        will then trigger custom events to continue further processing,
        especially since custom event handlers may run in individual threads.

        :param socket: Use an existing socket for the stream. Defaults to
                       ``None`` to generate a new socket.
        :param string host: The name of the target server.
        :param int port: The port to use for the connection. Defaults to 0.
        """

        transport: Transport | None

        # The socket that is used internally by the transport object
        socket: ssl.SSLSocket | None

        # The backoff of the connect routine (increases exponentially
        # after each failure)
        _connect_loop_wait: float

        parser: ET.XMLPullParser | None
        xml_depth: int
        xml_root: ET.Element | None

        waiting_queue: asyncio.Queue

        # A dict of {name: handle}
        scheduled_events: dict[str, TimerHandle]

        ssl_context: ssl.SSLContext

        # The event to trigger when the create_connection() succeeds. It can
        # be "connected" or "tls_success" depending on the step we are at.
        event_when_connected: str

        #: The list of accepted ciphers, in OpenSSL Format.
        #: It might be useful to override it for improved security
        #: over the python defaults.
        ciphers: str | None

        #: Path to a file containing certificates for verifying the
        #: server SSL certificate. A non-``None`` value will trigger
        #: certificate checking.
        #:
        #: .. note::
        #:
        #:     On Mac OS X, certificates in the system keyring will
        #:     be consulted, even if they are not in the provided file.
        ca_certs: Path | Iterable[Path] | None

        #: Path to a file containing a client certificate to use for
        #: authenticating via SASL EXTERNAL. If set, there must also
        #: be a corresponding `:attr:keyfile` value.
        certfile: str | None

        #: Path to a file containing the private key for the selected
        #: client certificate to use for authenticating via SASL EXTERNAL.
        keyfile: str | None

        # The asyncio event loop
        _loop: AbstractEventLoop | None

        #: The default port to return when querying DNS records.
        default_port: int

        #: The domain to try when querying DNS records.
        default_domain: str

        #: The expected name of the server, for validation.
        _expected_server_name: str
        _service_name: str

        #: A custom address to connect to that was provided to connect(). When
        #: using DNS lookups, this is not used. Once set, it will be re-used until
        #: connect() is called with no parameters (or both host and port set to
        #: None).
        custom_address: tuple[str, int] | None

        #: Enable connecting to the server directly over SSL, in
        #: particular when the service provides two ports: one for
        #: non-SSL traffic and another for SSL traffic.
        enable_direct_tls: bool
        #: Enable connecting to the server using STARTTLS (i.e. upgrading a clear
        #: connection once established).
        enable_starttls: bool
        #: Enable connecting to the server using plaintext
        #: strongly not recommended (unless for localhost components)
        enable_plaintext: bool

        #: If set to ``True``, attempt to use IPv6.
        use_ipv6: bool

        #: If set to ``True``, allow using the ``dnspython`` DNS library
        #: if available. If set to ``False``, the builtin DNS resolver
        #: will be used, even if ``dnspython`` is installed.
        use_aiodns: bool

        #: Use CDATA for escaping instead of XML entities. Defaults
        #: to ``False``.
        use_cdata: bool

        #: The default namespace of the stream content, not of the
        #: stream wrapper it
        default_ns: str

        default_lang: str | None
        peer_default_lang: str | None

        #: The namespace of the enveloping stream element.
        stream_ns: str

        #: The default opening tag for the stream element.
        stream_header: str

        #: The default closing tag for the stream element.
        stream_footer: str

        #: If ``True``, periodically send a whitespace character over the
        #: wire to keep the connection alive. Mainly useful for connections
        #: traversing NAT.
        whitespace_keepalive: bool

        #: The default interval between keepalive signals when
        #: :attr:`whitespace_keepalive` is enabled.
        whitespace_keepalive_interval: int

        #: Flag for controlling if the session can be considered ended
        #: if the connection is terminated.
        end_session_on_disconnect: bool

        #: A mapping of XML namespaces to well-known prefixes.
        namespace_map: dict

        __root_stanza: list[type[StanzaBase]]
        __handlers: list[BaseHandler]
        __event_handlers: dict[str, list[tuple[Handler, bool]]]
        __filters: _FiltersDict

        # Current connection attempt (Future)
        _current_connection_attempt: Future | None

        #: The reason why we are disconnecting from the server
        disconnect_reason: str | None

        #: An asyncio Future being done when the stream is disconnected.
        disconnected: Future

        # If the session has been started or not
        _session_started: bool
        # If we want to bypass the send() check (e.g. unit tests)
        _always_send_everything: bool

        _run_out_filters: Future | None
        __slow_tasks: list[Task]
        __queued_stanzas: list[tuple[StanzaBase | str, bool]]

        #: List of DNS SRV services records which map to TLS services
        tls_services: set[str]
        #: List of DNS SRV services records which map to STARTTLS services
        starttls_services: set[str]

        def __init__(self, host: str = '', port: int = 0,
                     ssl_context: ssl.SSLContext | None = None,
                     loop: asyncio.AbstractEventLoop | None = None):
            self.transport = None
            self.socket = None
            self._connect_loop_wait = 0

            self.parser = None
            self.xml_depth = 0
            self.xml_root = None

            self.waiting_queue = asyncio.Queue()

            # A dict of {name: handle}
            self.scheduled_events = {}

            if ssl_context is None:
                self.ssl_context = ssl.create_default_context()
                self.ssl_context.check_hostname = True
                self.ssl_context.verify_mode = ssl.CERT_REQUIRED
                self.ssl_context.set_default_verify_paths()
            else:
                self.ssl_context = ssl_context

            self.event_when_connected = "connected"

            self.ciphers = None

            self.ca_certs = None

            self.keyfile = None

            if loop:
                self._loop = loop
            else:
                self._loop = None
                # Let the loop be set by the getter
                self.loop

            self.default_port = int(port)
            self.default_domain = ''

            self._expected_server_name = ''
            self._service_name = ''

            self.custom_address = None

            self.enable_starttls = True
            self.enable_direct_tls = True
            self.enable_plaintext = False

            self.tls_services = set()
            self.starttls_services = set()
            self.use_ipv6 = True

            self.use_aiodns = True
            self.use_cdata = False

            self.default_ns = ''

            self.default_lang = None
            self.peer_default_lang = None

            self.stream_ns = ''
            self.stream_header = "<stream>"
            self.stream_footer = "</stream>"

            self.whitespace_keepalive = True
            self.whitespace_keepalive_interval = 300

            self.end_session_on_disconnect = True
            self.namespace_map = {StanzaBase.xml_ns: 'xml'}

            self.__root_stanza = []
            self.__handlers = []
            self.__event_handlers = {}
            self.__filters = {
                'in': [], 'out': [], 'out_sync': [], 'out_sce': []
            }

            self._current_connection_attempt = None

            self.disconnect_reason = None
            self.disconnected = Future(loop=self.loop)
            self._session_started = False
            self._always_send_everything = False

            self.add_event_handler('disconnected', self._remove_schedules)
            self.add_event_handler('disconnected', self._set_disconnected)
            self.add_event_handler('session_start', self._start_keepalive)
            self.add_event_handler('session_start', self._set_session_start)
            self.add_event_handler('session_resumed', self._set_session_start)

            self._run_out_filters = None
            self.__slow_tasks = []
            self.__queued_stanzas = []

        @property
        def loop(self) -> AbstractEventLoop:
            if self._loop is None:
                try:
                    # Python < 3.14
                    with warnings.catch_warnings():
                        warnings.simplefilter("ignore")
                        self._loop = asyncio.get_event_loop()
                except RuntimeError:
                    try:
                        current = asyncio.get_running_loop()
                    except RuntimeError:
                        current = None
                    if current is not None:
                        self._loop = current
                    else:
                        loop = asyncio.new_event_loop()
                        asyncio.set_event_loop(loop)
                        self._loop = loop
            return self._loop

        @loop.setter
        def loop(self, value: AbstractEventLoop) -> None:
            self._loop = value

        def new_id(self) -> str:
            """Generate and return a new stream ID in hexadecimal form.

            Many stanzas, handlers, or matchers may require unique
            ID values. Using this method ensures that all new ID values
            are unique in this stream.
            """
            return uuid.uuid4().hex

        def _set_session_start(self, event: Any) -> None:
            """
            On session start, queue all pending stanzas to be sent.
            """
            self._session_started = True
            for stanza in self.__queued_stanzas:
                self.waiting_queue.put_nowait(stanza)
            self.__queued_stanzas = []

        def _set_disconnected(self, event: Any) -> None:
            self._session_started = False

        def _set_disconnected_future(self) -> None:
            """Set the self.disconnected future on disconnect"""
            if not self.disconnected.done():
                self.disconnected.set_result(True)
            self.disconnected = asyncio.Future(loop=self.loop)

        def connect(self, host: str | None = None, port: int | None = None) -> asyncio.Future:
            """Create a new socket and connect to the server.

            :param host: The name of the desired server for the connection.
            :param port: Port to connect to on the server.
            :returns: A future on the current connection attempt
            """
            if self._run_out_filters is None or self._run_out_filters.done():
                self._run_out_filters = asyncio.ensure_future(
                    self.run_filters(),
                    loop=self.loop,
                )

            self.disconnect_reason = None
            self.cancel_connection_attempt()
            self._connect_loop_wait = 0
            if host and port:
                self.custom_address = (host, int(port))
            elif (host, port) == (None, None):
                self.custom_address = None

            self.event("connecting")
            self._current_connection_attempt = asyncio.ensure_future(
                self._connect_loop(),
                loop=self.loop,
            )
            return self._current_connection_attempt

        async def _connect_loop(self) -> asyncio.Future | None:
            """
            Loop over the various connection methods. Only wait minimally before
            retries within the same loop. If everything fails, the connection
            is rescheduled for later.
            """
            if self._connect_loop_wait > 0:
                self.event('reconnect_delay', self._connect_loop_wait)
                await asyncio.sleep(self._connect_loop_wait)
            if self.custom_address:
                host, port = self.custom_address
                records = [('', self.default_domain, host, port)]
            else:
                records = await self.get_dns_records(self.default_domain)
            if not records: # No DNS records
                records = [
                    ('', self.default_domain, self.default_domain, self.default_port),
                ]
            success = False
            for record in records:
                if success:
                    break
                service, host, address, dns_port = record
                tls = service in self.tls_services
                server_hostname = None
                if tls:
                    server_hostname = self.default_domain
                try:
                    if not service:
                        fake_services = []
                        if self.enable_direct_tls:
                            fake_services.extend(list(self.tls_services))
                        if self.enable_starttls:
                            fake_services.extend(list(self.starttls_services))
                        if self.enable_plaintext:
                            fake_services.extend([''])
                        for service in fake_services:
                            tls, server_hostname = (False, None)
                            if service in self.tls_services:
                                tls, server_hostname = True, self.default_domain
                            success = await self._attempt_connection(
                                address, dns_port, tls, server_hostname,
                            )
                            if success:
                                break
                    else:
                        success = await self._attempt_connection(
                            address, dns_port, tls, server_hostname,
                        )
                except Exception as exc:
                    log.error('Unhandled exception during connect(): %s',
                              exc, exc_info=True)
            if success:
                return None
            if self._current_connection_attempt is not None:
                return self.reschedule_connection_attempt()
            return None

        async def _attempt_connection(self, host: str, port: int, tls: bool,
                                      server_hostname: str | None) -> bool:
            """Try to connect to a remote server."""
            self.event_when_connected = "connected"
            self._connect_loop_wait += 1
            ssl_context: ssl.SSLContext | None = None
            if tls:
                ssl_context = self.get_ssl_context()

            if self._current_connection_attempt is None:
                return False
            try:
                await self.loop.create_connection(lambda: self,
                                                  host, port,
                                                  ssl=ssl_context,
                                                  server_hostname=server_hostname)
                self._connect_loop_wait = 0
                return True
            except Socket.gaierror:
                self.event('connection_failed',
                           'No DNS record available for %s' % self.default_domain)
                return False
            except OSError as e:
                log.debug('Connection failed: %s', e)
                self.event("connection_failed", e)
                return False

        def init_parser(self) -> None:
            """init the XML parser. The parser must always be reset for each new
            connexion
            """
            self.xml_depth = 0
            self.xml_root = None
            self.parser = ET.XMLPullParser(("start", "end"))

        def connection_made(self, transport: BaseTransport, send_event: bool = True) -> None:
            """Called when the TCP connection has been established with the server
            """
            if send_event:
                self.event(self.event_when_connected)
            self.transport = cast(Transport, transport)
            if self.transport is None:
                raise ValueError("Transport cannot be none")
            self.socket = self.transport.get_extra_info(
                "ssl_object",
                default=self.transport.get_extra_info("socket")
            )
            ssl_object = transport.get_extra_info(
                "ssl_object",
                default=None,
            )
            if ssl_object is not None:
                der_cert = ssl_object.getpeercert(True)
                pem_cert = ssl.DER_cert_to_PEM_cert(der_cert)
                self.event('ssl_cert', pem_cert)
                if self._current_connection_attempt is None:
                    # Connection attempt aborted
                    return
                self.event('tls_success')
            self._current_connection_attempt = None
            self.init_parser()
            self.send_raw(self.stream_header)

        def data_received(self, data: bytes | str) -> None:
            """Called when incoming data is received on the socket.

            We feed that data to the parser and the see if this produced any XML
            event.  This could trigger one or more event (a stanza is received,
            the stream is opened, etc).
            """
            if self.parser is None:
                log.warning('Received data before the connection is established: %r',
                            data)
                return
            self.parser.feed(data)
            try:
                for event, xml in self.parser.read_events():  # type:ignore[misc]
                    xml = cast(ET.Element, xml)
                    if event == 'start':
                        if self.xml_depth == 0:
                            # We have received the start of the root element.
                            self.xml_root = xml
                            log.debug('RECV: %s', tostring(self.xml_root,
                                                           xmlns=self.default_ns,
                                                           stream=self,
                                                           top_level=True,
                                                           open_only=True))
                            self.start_stream_handler(self.xml_root)  # type:ignore
                        self.xml_depth += 1
                    if event == 'end':
                        self.xml_depth -= 1
                        if self.xml_depth == 0:
                            # The stream's root element has closed,
                            # terminating the stream.
                            log.debug("End of stream received")
                            self.disconnect_reason = "End of stream"
                            self.abort()
                            return
                        elif self.xml_depth == 1:
                            # A stanza is an XML element that is a direct child of
                            # the root element, hence the check of depth == 1
                            self._spawn_event(xml)
                            if self.xml_root is not None:
                                # Keep the root element empty of children to
                                # save on memory use.
                                self.xml_root.clear()
            except ET.ParseError:
                log.error('Parse error: %r', data)

                # Due to cyclic dependencies, this can’t be imported at the module
                # level.
                from slixmpp.stanza.stream_error import StreamError
                error = StreamError()
                error['condition'] = 'not-well-formed'
                error['text'] = 'Server sent: %r' % data
                self.send(error)
                self.disconnect()

        def is_connecting(self) -> bool:
            return self._current_connection_attempt is not None

        def is_connected(self) -> bool:
            return self.transport is not None

        def eof_received(self) -> None:
            """When the TCP connection is properly closed by the remote end
            """
            self.event("eof_received")

        def connection_lost(self, exception: BaseException | None) -> None:
            """On any kind of disconnection, initiated by us or not.  This signals the
            closure of the TCP connection
            """
            log.info("connection_lost: %s", (exception,))
            # All these objects are associated with one TCP connection.  Since
            # we are not connected anymore, destroy them
            self.parser = None
            self.transport = None
            self.socket = None
            # Fire the events after cleanup
            if self.end_session_on_disconnect:
                self._reset_sendq()
                self.event('session_end')
            self._set_disconnected_future()
            self.event("disconnected", self.disconnect_reason or exception)

        def reschedule_connection_attempt(self) -> asyncio.Future | None:
            """
            Increase the exponential back-off and initiate another background
            _connect_loop call to connect to the server.

            :returns: A future on the next scheduled connection attempt.
            """
            # abort if there is no ongoing connection attempt
            if self._current_connection_attempt is None:
                return None
            self._connect_loop_wait = min(300, self._connect_loop_wait * 2 + 1)
            self._current_connection_attempt = asyncio.ensure_future(
                self._connect_loop(),
                loop=self.loop,
            )
            return self._current_connection_attempt

        def cancel_connection_attempt(self) -> None:
            """
            Immediately cancel the current create_connection() Future.
            This is useful when a client using slixmpp tries to connect
            on flaky networks, where sometimes a connection just gets lost
            and it needs to reconnect while the attempt is still ongoing.
            """
            if self._current_connection_attempt:
                self._current_connection_attempt.cancel()
                self._current_connection_attempt = None

        def disconnect(self, wait: float | int = 2.0, reason: str | None = None, ignore_send_queue: bool = False) -> Future:
            """Close the XML stream and wait for an acknowldgement from the server for
            at most `wait` seconds.  After the given number of seconds has
            passed without a response from the server, or when the server
            successfully responds with a closure of its own stream, abort() is
            called. If wait is 0.0, this will call abort() directly without closing
            the stream.

            Does nothing but trigger the disconnected event if we are not connected.

            :param wait: Time to wait for a response from the server.
            :param reason: An optional reason for the disconnect.
            :param ignore_send_queue: Boolean to toggle if we want to ignore
                                      the in-flight stanzas and disconnect immediately.
            :return: A future that ends when all code involved in the disconnect has ended
            """
            # Compat: docs/getting_started/sendlogout.rst has been promoting
            # `disconnect(wait=True)` for ages. This doesn't mean anything to the
            # schedule call below. It would fortunately be converted to `1` later
            # down the call chain. Praise the implicit casts lord.
            if wait is True:
                wait = 2.0

            if self.transport:
                self.disconnect_reason = reason
                if self.waiting_queue.empty() or ignore_send_queue:
                    self.cancel_connection_attempt()
                    return asyncio.ensure_future(
                        self._end_stream_wait(wait, reason=reason),
                        loop=self.loop,
                    )
                else:
                    return asyncio.ensure_future(
                        self._consume_send_queue_before_disconnecting(reason, wait),
                        loop=self.loop,
                    )
            else:
                self._set_disconnected_future()
                self.event("disconnected", reason)
                future: Future = Future(loop=self.loop)
                future.set_result(None)
                return future

        async def _consume_send_queue_before_disconnecting(self, reason: str | None, wait: float) -> None:
            """Wait until the send queue is empty before disconnecting"""
            try:
                await asyncio.wait_for(
                    self.waiting_queue.join(),
                    wait,
                )
            except asyncio.TimeoutError:
                wait = 0 # we already consumed the timeout
            self.disconnect_reason = reason
            await self._end_stream_wait(wait)

        async def _end_stream_wait(self, wait: int | float = 2, reason: str | None = None) -> None:
            """
            Run abort() if we do not received the disconnected event
            after a waiting time.

            :param wait: The waiting time (defaults to 2)
            """
            try:
                self.send_raw(self.stream_footer)
                await self.wait_until('disconnected', wait)
            except asyncio.TimeoutError:
                self.abort()
            except NotConnectedError:
                # We are not connected when sending the end of stream
                # that means the disconnect has already been handled
                pass

        def abort(self) -> None:
            """
            Forcibly close the connection
            """
            if self.transport:
                self.cancel_connection_attempt()
                self.transport.close()
                self.transport.abort()
                self.event("killed")

        def reconnect(self, wait: int | float = 2.0, reason: str = "Reconnecting") -> None:
            """Calls disconnect(), and once we are disconnected (after the timeout, or
            when the server acknowledgement is received), call connect()
            """
            log.debug("reconnecting...")
            async def handler(event: Any) -> None:
                # We yield here to allow synchronous handlers to work first
                await asyncio.sleep(0)
                host, port = None, None
                if self.custom_address:
                    host, port = self.custom_address
                self.connect(host=host, port=port)
            self.add_event_handler('disconnected', handler, disposable=True)
            self.disconnect(wait, reason)

        def configure_socket(self) -> None:
            """Set timeout and other options for self.socket.

            Meant to be overridden.
            """
            pass

        def configure_dns(self, resolver: Any, domain: str | None = None, port: int | None = None) -> None:
            """
            Configure and set options for a :class:`~dns.resolver.Resolver`
            instance, and other DNS related tasks. For example, you
            can also check :meth:`~socket.socket.getaddrinfo` to see
            if you need to call out to ``libresolv.so.2`` to
            run ``res_init()``.

            Meant to be overridden.

            :param resolver: A :class:`~dns.resolver.Resolver` instance
                             or ``None`` if ``dnspython`` is not installed.
            :param domain: The initial domain under consideration.
            :param port: The initial port under consideration.
            """
            pass

        def get_ssl_context(self) -> ssl.SSLContext:
            """
            Get SSL context.
            """
            if self.ciphers is not None:
                self.ssl_context.set_ciphers(self.ciphers)
            if self.keyfile and self.certfile:
                try:
                    self.ssl_context.load_cert_chain(self.certfile, self.keyfile)
                except (ssl.SSLError, OSError):
                    log.debug('Error loading the cert chain:', exc_info=True)
                else:
                    log.debug('Loaded cert file %s and key file %s',
                              self.certfile, self.keyfile)
            if self.ca_certs is not None:
                ca_cert: Path | None = None
                # XXX: Compat before d733c54518.
                if isinstance(self.ca_certs, str):
                    self.ca_certs = Path(self.ca_certs)
                if isinstance(self.ca_certs, Path):
                    if self.ca_certs.is_file():
                        ca_cert = self.ca_certs
                else:
                    for bundle in self.ca_certs:
                        if bundle.is_file():
                            ca_cert = bundle
                            break
                if ca_cert is None and \
                   isinstance(self.ca_certs, (Path, collections.abc.Iterable)):
                    raise InvalidCABundle(self.ca_certs)

                self.ssl_context.verify_mode = ssl.CERT_REQUIRED
                self.ssl_context.load_verify_locations(cafile=ca_cert)

            return self.ssl_context

        async def start_tls(self) -> bool:
            """Perform handshakes for TLS.

            If the handshake is successful, the XML stream will need
            to be restarted.
            """
            if self.transport is None:
                raise ValueError("Transport should not be None")
            ssl_context = self.get_ssl_context()
            try:
                self._current_connection_attempt = asyncio.ensure_future(
                    self.loop.start_tls(self.transport,
                                        self, ssl_context,
                                        server_hostname=self.default_domain),
                    loop=self.loop,
                )
                transp = await self._current_connection_attempt
            except ssl.SSLError as e:
                log.debug('SSL: Unable to connect', exc_info=True)
                log.error('CERT: Invalid certificate trust chain.')
                if not self.event_handled('ssl_invalid_chain'):
                    self.disconnect()
                else:
                    self.event('ssl_invalid_chain', e)
                return False
            except OSError:
                log.debug("Connection error:", exc_info=True)
                self.disconnect()
                return False
            if transp is None:
                raise Exception("Transport should not be none")
            # If we use the builtin start_tls, the connection_made() protocol
            # method is not called automatically
            if hasattr(self.loop, 'start_tls'):
                self.connection_made(transp, send_event=False)
            return True

        def _start_keepalive(self, event: Any) -> None:
            """Begin sending whitespace periodically to keep the connection alive.

            May be disabled by setting::

                self.whitespace_keepalive = False

            The keepalive interval can be set using::

                self.whitespace_keepalive_interval = 300
            """
            self.schedule('Whitespace Keepalive',
                          self.whitespace_keepalive_interval,
                          self.send_raw,
                          args=(' ',),
                          repeat=True)

        def _remove_schedules(self, event: Any) -> None:
            """Remove some schedules that become pointless when disconnected"""
            self.cancel_schedule('Whitespace Keepalive')

        def start_stream_handler(self, xml: ET.Element) -> None:
            """Perform any initialization actions, such as handshakes,
            once the stream header has been sent.

            Meant to be overridden.
            """
            pass

        def register_stanza(self, stanza_class: type[StanzaBase]) -> None:
            """Add a stanza object class as a known root stanza.

            A root stanza is one that appears as a direct child of the stream's
            root element.

            Stanzas that appear as substanzas of a root stanza do not need to
            be registered here. That is done using register_stanza_plugin() from
            slixmpp.xmlstream.stanzabase.

            Stanzas that are not registered will not be converted into
            stanza objects, but may still be processed using handlers and
            matchers.

            :param stanza_class: The top-level stanza object's class.
            """
            self.__root_stanza.append(stanza_class)

        def remove_stanza(self, stanza_class: type[StanzaBase]) -> None:
            """Remove a stanza from being a known root stanza.

            A root stanza is one that appears as a direct child of the stream's
            root element.

            Stanzas that are not registered will not be converted into
            stanza objects, but may still be processed using handlers and
            matchers.
            """
            self.__root_stanza.remove(stanza_class)

        def add_filter(self, mode: FilterString, handler: Filter, order: int | None = None) -> None:
            """Add a filter for incoming or outgoing stanzas.

            These filters are applied before incoming stanzas are
            passed to any handlers, and before outgoing stanzas
            are put in the send queue.

            Each filter must accept a single stanza, and return
            either a stanza or ``None``. If the filter returns
            ``None``, then the stanza will be dropped from being
            processed for events or from being sent.

            There are multiple "modes" of filters for incoming and
            outgoing stanzas. These modes differ in the order they
            are processed, as well as whether the filters can be
            sync or async. For the outgoing direction, the filters
            of mode ``'out'`` are processed first. Whether a filter
            in this mode is sync or async is determined by
            inspecting it. Next, the mode ``'out_sync'`` is
            processed, which treats all filters as sync. Finally,
            the mode ``'out_sce'`` is processed, which is reserved
            for filters applying XEP-0420 Stanza Content Encryption
            or comparable processing to the whole stanza. These can
            be sync or async, detected automatically. For the
            incoming direction, the only available mode is ``'in'``,
            which only accepts sync filters.

            :param mode: One of ``'in'``, ``'out'``, ``'out_sync'``
                         or ``'out_sce'``.
            :param handler: The filter function.
            :param int order: The position to insert the filter in
                              the list of active filters for that
                              mode.
            """
            if order:
                self.__filters[mode].insert(order, handler)
            else:
                self.__filters[mode].append(handler)

        def del_filter(self, mode: str, handler: Callable[[StanzaBase], StanzaBase | None]) -> None:
            """Remove an incoming or outgoing filter."""
            self.__filters[mode].remove(handler)

        def register_handler(self, handler: BaseHandler, before: BaseHandler | None = None, after: BaseHandler | None = None) -> None:
            """Add a stream event handler that will be executed when a matching
            stanza is received.

            :param handler:
                    The :class:`~slixmpp.xmlstream.handler.base.BaseHandler`
                    derived object to execute.
            """
            if handler.stream is None:
                self.__handlers.append(handler)
                handler.stream = weakref.ref(self)

        def remove_handler(self, name: str) -> bool:
            """Remove any stream event handlers with the given name.

            :param name: The name of the handler.
            """
            idx = 0
            for handler in self.__handlers:
                if handler.name == name:
                    self.__handlers.pop(idx)
                    return True
                idx += 1
            return False

        async def get_dns_records(self, domain: str, port: int | None = None) -> list[tuple[str, str, str, int]]:
            """Get the DNS records for a domain.

            :param domain: The domain in question.
            :param port: If the results don't include a port, use this one.
            """
            if port is None:
                port = self.default_port

            resolver = default_resolver(loop=self.loop)
            self.configure_dns(resolver, domain=domain, port=port)

            services = []
            if self.enable_direct_tls:
                services.extend(list(self.tls_services))
            if self.enable_starttls:
                services.extend(list(self.starttls_services))
            result = await resolve(domain, port,
                                   services=services,
                                   resolver=resolver,
                                   use_ipv6=self.use_ipv6,
                                   use_aiodns=self.use_aiodns,
                                   loop=self.loop)
            return result

        def add_event_handler(self, name: str, pointer: Callable[..., Any], disposable: bool = False) -> None:
            """Add a custom event handler that will be executed whenever
            its event is manually triggered.

            :param name: The name of the event that will trigger
                         this handler.
            :param pointer: The function to execute.
            :param disposable: If set to ``True``, the handler will be
                               discarded after one use. Defaults to ``False``.
            """
            if name not in self.__event_handlers:
                self.__event_handlers[name] = []
            self.__event_handlers[name].append((pointer, disposable))

        def del_event_handler(self, name: str, pointer: Callable[..., Any]) -> None:
            """Remove a function as a handler for an event.

            :param name: The name of the event.
            :param pointer: The function to remove as a handler.
            """
            if name not in self.__event_handlers:
                return

            # Need to keep handlers that do not use
            # the given function pointer
            def filter_pointers(handler: tuple[Callable[..., Any], bool]) -> bool:
                return handler[0] != pointer

            self.__event_handlers[name] = list(filter(
                filter_pointers,
                self.__event_handlers[name]))

        def event_handled(self, name: str) -> int:
            """Returns the number of registered handlers for an event.

            :param name: The name of the event to check.
            """
            return len(self.__event_handlers.get(name, []))

        async def event_async(self, name: str, data: Any = {}) -> None:
            """Manually trigger a custom event, but await coroutines immediately.

            This event generator should only be called in situations when
            in-order processing of events is important, such as features
            handling.

            :param name: The name of the event to trigger.
            :param data: Data that will be passed to each event handler.
                         Defaults to an empty dictionary, but is usually
                         a stanza object.
            """
            handlers = self.__event_handlers.get(name, [])[:]
            for handler in handlers:
                handler_callback, disposable = handler
                if disposable:
                    # If the handler is disposable, we will go ahead and
                    # remove it now instead of waiting for it to be
                    # processed in the queue.
                    try:
                        self.__event_handlers[name].remove(handler)
                    except ValueError:
                        pass
                # If the callback is a coroutine, schedule it instead of
                # running it directly
                if iscoroutinefunction(handler_callback):
                    try:
                        await handler_callback(data)
                    except Exception as exc:
                        self.exception(exc)
                else:
                    try:
                        handler_callback(data)
                    except Exception as e:
                        self.exception(e)

        def event(self, name: str, data: Any = {}) -> None:
            """Manually trigger a custom event.
            Coroutine handlers are wrapped into a future and sent into the
            event loop for their execution, and not awaited.

            :param name: The name of the event to trigger.
            :param data: Data that will be passed to each event handler.
                         Defaults to an empty dictionary, but is usually
                         a stanza object.
            """
            log.debug("Event triggered: %s", name)

            handlers = self.__event_handlers.get(name, [])[:]
            for handler in handlers:
                handler_callback, disposable = handler
                old_exception = getattr(data, 'exception', None)

                # If the callback is a coroutine, schedule it instead of
                # running it directly
                if iscoroutinefunction(handler_callback):
                    async def handler_callback_routine(cb: Callable[[ElementBase], Any]) -> None:
                        try:
                            await cb(data)
                        except Exception as e:
                            if old_exception:
                                old_exception(e)
                            else:
                                self.exception(e)
                    asyncio.ensure_future(
                        handler_callback_routine(handler_callback),
                        loop=self.loop,
                    )
                else:
                    try:
                        handler_callback(data)
                    except Exception as e:
                        if old_exception:
                            old_exception(e)
                        else:
                            self.exception(e)
                if disposable:
                    # If the handler is disposable, we will go ahead and
                    # remove it now instead of waiting for it to be
                    # processed in the queue.
                    try:
                        self.__event_handlers[name].remove(handler)
                    except ValueError:
                        pass

        def schedule(self, name: str, seconds: int, callback: Callable[..., None],
                args: tuple[Any, ...] = tuple(),
                kwargs: dict[Any, Any] = {}, repeat: bool = False) -> None:
            """Schedule a callback function to execute after a given delay.

            :param name: A unique name for the scheduled callback.
            :param seconds: The time in seconds to wait before executing.
            :param callback: A pointer to the function to execute.
            :param args: A tuple of arguments to pass to the function.
            :param kwargs: A dictionary of keyword arguments to pass to
                           the function.
            :param repeat: Flag indicating if the scheduled event should
                           be reset and repeat after executing.
            """
            if name in self.scheduled_events:
                raise ValueError(
                    "There is already a scheduled event of name: %s" % name)
            if seconds is None:
                seconds = RESPONSE_TIMEOUT
            cb = functools.partial(callback, *args, **kwargs)
            if repeat:
                handle = self.loop.call_later(seconds, self._execute_and_reschedule,
                                              name, cb, seconds)
            else:
                handle = self.loop.call_later(seconds, self._execute_and_unschedule,
                                              name, cb)
            # Save that handle, so we can just cancel this scheduled event by
            # canceling scheduled_events[name]
            self.scheduled_events[name] = handle

        def cancel_schedule(self, name: str) -> None:
            try:
                handle = self.scheduled_events.pop(name)
                handle.cancel()
            except KeyError:
                log.debug("Tried to cancel unscheduled event: %s" % (name,))

        def _safe_cb_run(self, name: str, cb: Callable[[], None]) -> None:
            log.debug('Scheduled event: %s', name)
            try:
                cb()
            except Exception as e:
                self.exception(e)

        def _execute_and_reschedule(self, name: str, cb: Callable[[], None], seconds: int) -> None:
            """Simple method that calls the given callback, and then schedule itself to
            be called after the given number of seconds.
            """
            self._safe_cb_run(name, cb)
            handle = self.loop.call_later(seconds, self._execute_and_reschedule,
                                          name, cb, seconds)
            self.scheduled_events[name] = handle

        def _execute_and_unschedule(self, name: str, cb: Callable[[], None]) -> None:
            """
            Execute the callback and remove the handler for it.
            """
            self._safe_cb_run(name, cb)
            # workaround for specific events which unschedule themselves
            if name in self.scheduled_events:
                del self.scheduled_events[name]

        def incoming_filter(self, xml: ET.Element) -> ET.Element:
            """Filter incoming XML objects before they are processed.

            Possible uses include remapping namespaces, or correcting elements
            from sources with incorrect behavior.

            Meant to be overridden.
            """
            return xml

        def _reset_sendq(self) -> None:
            """Clear sending tasks on session end"""
            # Cancel all pending slow send tasks
            log.debug('Cancelling %d slow send tasks', len(self.__slow_tasks))
            for slow_task in self.__slow_tasks:
                slow_task.cancel()
            self.__slow_tasks.clear()
            # Purge pending stanzas
            while not self.waiting_queue.empty():
                discarded = self.waiting_queue.get_nowait()
                log.debug('Discarded stanza: %s', discarded)

        async def _continue_slow_send(
                self,
                task: asyncio.Task,
                already_used: set[Filter]
        ) -> None:
            """
            Used when an item in the send queue has taken too long to process.

            This is away from the send queue and can take as much time as needed.
            :param asyncio.Task task: the Task wrapping the coroutine
            :param set already_used: Filters already used on this outgoing stanza
            """
            data = await task
            self.__slow_tasks.remove(task)
            if data is None:
                return

            for filter_mode in ['out', 'out_sync', 'out_sce']:
                for filter in self.__filters[filter_mode][:]:
                    if filter in already_used:
                        continue
                    is_async_filter = iscoroutinefunction(filter)
                    if filter_mode == 'out_sync':
                        # Assume these are sync without checking
                        is_async_filter = False
                    if is_async_filter:
                        filter = cast(AsyncFilter, filter)
                        data = await filter(data)  # type: ignore
                    else:
                        filter = cast(SyncFilter, filter)
                        data = filter(data)
                    if data is None:
                        return

            str_data = tostring(data.xml, xmlns=self.default_ns,
                                stream=self, top_level=True)
            self.send_raw(str_data)

        async def run_filters(self) -> None:
            """
            Background loop that processes stanzas to send.
            """
            while True:
                data: StanzaBase | str | None
                (data, use_filters) = await self.waiting_queue.get()
                try:
                    if use_filters and isinstance(data, StanzaBase):
                        already_run_filters = set()
                        for filter_mode in ['out', 'out_sync', 'out_sce']:
                            for filter in self.__filters[filter_mode]:
                                already_run_filters.add(filter)
                                is_async_filter = iscoroutinefunction(filter)
                                if filter_mode == 'out_sync':
                                    # Assume these are sync without checking
                                    is_async_filter = False
                                if is_async_filter:
                                    filter = cast(AsyncFilter, filter)
                                    task = asyncio.create_task(filter(data))  # type:ignore
                                    completed, pending = await wait(
                                        {task},
                                        timeout=1,
                                    )
                                    if pending:
                                        self.__slow_tasks.append(task)
                                        asyncio.ensure_future(
                                            self._continue_slow_send(
                                                task,
                                                already_run_filters
                                            ),
                                            loop=self.loop,
                                        )
                                        raise ContinueQueue(
                                            "Slow coroutine, rescheduling filters"
                                        )
                                    data = task.result()
                                elif isinstance(data, StanzaBase):
                                    filter = cast(SyncFilter, filter)
                                    data = filter(data)
                                if data is None:
                                    raise ContinueQueue('Empty stanza')

                    if isinstance(data, StanzaBase):
                        str_data = tostring(data.xml, xmlns=self.default_ns,
                                            stream=self, top_level=True)
                        self.send_raw(str_data)
                    elif isinstance(data, (str, bytes)):
                        self.send_raw(data)
                except ContinueQueue as exc:
                    log.debug('Stanza in send queue not sent: %s', exc)
                except asyncio.CancelledError:
                    log.debug('Send coroutine received cancel(), stopping')
                    return
                except Exception:
                    log.error('Exception raised in send queue:', exc_info=True)
                self.waiting_queue.task_done()

        def send(self, data: StanzaBase | str, use_filters: bool = True) -> None:
            """A wrapper for :meth:`send_raw()` for sending stanza objects.

            :param data: The :class:`~slixmpp.xmlstream.stanzabase.StanzaBase`
                         stanza to send on the stream.
            :param bool use_filters: Indicates if outgoing filters should be
                                     applied to the given stanza data. Disabling
                                     filters is useful when resending stanzas.
                                     Defaults to ``True``.
            """
            # When not connected, allow features/starttls/etc to go through
            # but not stanzas or arbitrary payloads.
            if not self._always_send_everything and not self._session_started:
                # Avoid circular imports
                from slixmpp.stanza.rootstanza import RootStanza
                from slixmpp.stanza import Iq, Handshake

                passthrough = False
                if isinstance(data, Iq):
                    if data.get_plugin('bind', check=True):
                        passthrough = True
                    elif data.get_plugin('session', check=True):
                        passthrough = True
                    elif data.get_plugin('register', check=True):
                        passthrough = True
                elif isinstance(data, Handshake):
                    passthrough = True

                if isinstance(data, (RootStanza, str)) and not passthrough:
                    self.__queued_stanzas.append((data, use_filters))
                    log.debug('NOT SENT: %s %s', type(data), data)
                    self.event('stanza_not_sent', data)
                    return
            self.waiting_queue.put_nowait((data, use_filters))

        def send_xml(self, data: ET.Element) -> None:
            """Send an XML object on the stream

            :param data: The :class:`~xml.etree.ElementTree.Element` XML object
                         to send on the stream.
            """
            self.send(tostring(data))

        def send_raw(self, data: str | bytes) -> None:
            """Send raw data across the stream.

            :param string data: Any bytes or utf-8 string value.
            """
            log.debug("SEND: %s", data)
            if not self.transport:
                raise NotConnectedError()
            if isinstance(data, str):
                data = data.encode('utf-8')
            self.transport.write(data)

        def _build_stanza(self, xml: ET.Element,
                          default_ns: str | None = None) -> StanzaBase:
            """Create a stanza object from a given XML object.

            If a specialized stanza type is not found for the XML, then
            a generic :class:`~slixmpp.xmlstream.stanzabase.StanzaBase`
            stanza will be returned.

            :param xml: The :class:`~xml.etree.ElementTree.Element` XML object
                        to convert into a stanza object.
            :param default_ns: Optional default namespace to use instead of the
                               stream's current default namespace.
            """
            if default_ns is None:
                default_ns = self.default_ns
            stanza_type = StanzaBase
            for stanza_class in self.__root_stanza:
                if xml.tag == "{%s}%s" % (default_ns, stanza_class.name) or \
                   xml.tag == stanza_class.tag_name():
                    stanza_type = stanza_class
                    break
            stanza = stanza_type(self, xml, recv=True)
            if stanza['lang'] is None and self.peer_default_lang:
                stanza['lang'] = self.peer_default_lang
            return stanza

        def _spawn_event(self, xml: ET.Element) -> None:
            """
            Analyze incoming XML stanzas and convert them into stanza
            objects if applicable and queue stream events to be processed
            by matching handlers.

            :param xml: The :class:`~slixmpp.xmlstream.stanzabase.ElementBase`
                        stanza to analyze.
            """
            # Apply any preprocessing filters.
            xml = self.incoming_filter(xml)

            # Convert the raw XML object into a stanza object. If no registered
            # stanza type applies, a generic StanzaBase stanza will be used.
            try:
                stanza: StanzaBase | None = self._build_stanza(xml)
            except Exception as exc:
                log.exception("Unable to parse stanza: %s,\n%s", exc, xml)
                stanza = None
            if stanza is None:
                return

            self.recv_stanza(stanza)

        def recv_stanza(self, stanza: StanzaBase) -> None:
            """
            Process a stanza that was just received or decrypted. Queue stream
            events to be processed by matching handlers.

            :param stanza: The :class:`~slixmpp.xmlstream.stanzabase.StanzaBase`
                           stanza to process.
            """
            for filter in self.__filters['in']:
                filter = cast(SyncFilter, filter)
                stanza_filtered = filter(stanza)
                if stanza_filtered is None:
                    return
                stanza = stanza_filtered

            log.debug("RECV: %s", stanza)

            # Match the stanza against registered handlers. Handlers marked
            # to run "in stream" will be executed immediately; the rest will
            # be queued.
            handled = False
            matched_handlers = [h for h in self.__handlers if h.match(stanza)]
            for handler in matched_handlers:
                handler.prerun(stanza)
                try:
                    handler.run(stanza)
                except Exception as e:
                    stanza.exception(e)
                if handler.check_delete():
                    self.__handlers.remove(handler)
                handled = True

            # Some stanzas require responses, such as Iq queries. A default
            # handler will be executed immediately for this case.
            if not handled:
                stanza.unhandled()

        def exception(self, exception: Exception) -> None:
            """Process an unknown exception.

            Meant to be overridden.

            :param exception: An unhandled exception object.
            """
            pass

        async def wait_until(self, event: str, timeout: int | float = 30) -> Any:
            """Utility method to wake on the next firing of an event.
            (Registers a disposable handler on it)

            :param str event: Event to wait on.
            :param int timeout: Timeout
            :raises: :class:`asyncio.TimeoutError` when the timeout is reached
            """
            fut: Future = asyncio.Future(loop=self.loop)

            def result_handler(event_data: Any) -> None:
                if not fut.done():
                    fut.set_result(event_data)
                else:
                    log.debug(
                        "Future registered on event '%s' was already done",
                        event
                    )

            self.add_event_handler(
                event,
                result_handler,
                disposable=True,
            )
            return await asyncio.wait_for(fut, timeout)

        @contextmanager
        def event_handler(self, event: str, handler: Callable[..., Any]) -> Generator[None, None, None]:
            """
            Context manager that adds then removes an event handler.
            """
            self.add_event_handler(event, handler)
            try:
                yield
            except Exception:
                raise
            finally:
                self.del_event_handler(event, handler)

        def wrap(self, coroutine: Awaitable[T]) -> Future[T]:
            """Make a Future out of a coroutine or another awaitable
            with the current loop.

            :param coroutine: The coroutine to wrap.
            """
            return asyncio.ensure_future(
                coroutine,
                loop=self.loop,
            )

        def __del__(self) -> None:
            if self._run_out_filters is not None:
                self._run_out_filters.cancel()