# Source code for cassandra.io.twistedreactor

    # Copyright DataStax, Inc.
    #
    # 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.
    """
    Module that implements an event loop based on twisted
    ( https://twistedmatrix.com ).
    """
    import atexit
    import logging
    import time
    from functools import partial
    from threading import Thread, Lock
    import weakref

    from twisted.internet import reactor, protocol
    from twisted.internet.endpoints import connectProtocol, TCP4ClientEndpoint, SSL4ClientEndpoint
    from twisted.internet.interfaces import IOpenSSLClientConnectionCreator
    from twisted.python.failure import Failure
    from zope.interface import implementer

    from cassandra.connection import Connection, ConnectionShutdown, Timer, TimerManager, ConnectionException

    try:
        from OpenSSL import SSL
        _HAS_SSL = True
    except ImportError as e:
        _HAS_SSL = False
        import_exception = e
    log = logging.getLogger(__name__)

    def _cleanup(cleanup_weakref):
        try:
            cleanup_weakref()._cleanup()
        except ReferenceError:
            return

    class TwistedConnectionProtocol(protocol.Protocol):
        """
        Twisted Protocol class for handling data received and connection
        made events.
        """

        def __init__(self, connection):
            self.connection = connection

        def dataReceived(self, data):
            """
            Callback function that is called when data has been received
            on the connection.

            Reaches back to the Connection object and queues the data for
            processing.
            """
            self.connection._iobuf.write(data)
            self.connection.handle_read()

        def connectionMade(self):
            """
            Callback function that is called when a connection has succeeded.

            Reaches back to the Connection object and confirms that the connection
            is ready.
            """
            self.connection.client_connection_made(self.transport)

        def connectionLost(self, reason):
            # reason is a Failure instance
            log.debug("Connect lost: %s", reason)
            self.connection.defunct(reason.value)

    class TwistedLoop(object):

        _lock = None
        _thread = None
        _timeout_task = None
        _timeout = None

        def __init__(self):
            self._lock = Lock()
            self._timers = TimerManager()

        def maybe_start(self):
            with self._lock:
                if not reactor.running:
                    self._thread = Thread(target=reactor.run,
                                          name="cassandra_driver_twisted_event_loop",
                                          kwargs={'installSignalHandlers': False})
                    self._thread.daemon = True
                    self._thread.start()
                    atexit.register(partial(_cleanup, weakref.ref(self)))

        def _cleanup(self):
            if self._thread:
                reactor.callFromThread(reactor.stop)
                self._thread.join(timeout=1.0)
                if self._thread.is_alive():
                    log.warning("Event loop thread could not be joined, so "
                                "shutdown may not be clean. Please call "
                                "Cluster.shutdown() to avoid this.")
                log.debug("Event loop thread was joined")

        def add_timer(self, timer):
            self._timers.add_timer(timer)
            # callFromThread to schedule from the loop thread, where
            # the timeout task can safely be modified
            reactor.callFromThread(self._schedule_timeout, timer.end)

        def _schedule_timeout(self, next_timeout):
            if next_timeout:
                delay = max(next_timeout - time.time(), 0)
                if self._timeout_task and self._timeout_task.active():
                    if next_timeout < self._timeout:
                        self._timeout_task.reset(delay)
                        self._timeout = next_timeout
                else:
                    self._timeout_task = reactor.callLater(delay, self._on_loop_timer)
                    self._timeout = next_timeout

        def _on_loop_timer(self):
            self._timers.service_timeouts()
            self._schedule_timeout(self._timers.next_timeout)

    @implementer(IOpenSSLClientConnectionCreator)
    class _SSLCreator(object):
        def __init__(self, endpoint, ssl_context, ssl_options, check_hostname, timeout):
            self.endpoint = endpoint
            self.ssl_options = ssl_options
            self.check_hostname = check_hostname
            self.timeout = timeout

            if ssl_context:
                self.context = ssl_context
            else:
                self.context = SSL.Context(SSL.TLSv1_METHOD)
                if "certfile" in self.ssl_options:
                    self.context.use_certificate_file(self.ssl_options["certfile"])
                if "keyfile" in self.ssl_options:
                    self.context.use_privatekey_file(self.ssl_options["keyfile"])
                if "ca_certs" in self.ssl_options:
                    self.context.load_verify_locations(self.ssl_options["ca_certs"])
                if "cert_reqs" in self.ssl_options:
                    self.context.set_verify(
                        self.ssl_options["cert_reqs"],
                        callback=self.verify_callback
                    )
            self.context.set_info_callback(self.info_callback)

        def verify_callback(self, connection, x509, errnum, errdepth, ok):
            return ok

        def info_callback(self, connection, where, ret):
            if where & SSL.SSL_CB_HANDSHAKE_DONE:
                if self.check_hostname and self.endpoint.address != connection.get_peer_certificate().get_subject().commonName:
                    transport = connection.get_app_data()
                    transport.failVerification(Failure(ConnectionException("Hostname verification failed", self.endpoint)))

        def clientConnectionForTLS(self, tlsProtocol):
            connection = SSL.Connection(self.context, None)
            connection.set_app_data(tlsProtocol)
            if self.ssl_options and "server_hostname" in self.ssl_options:
                connection.set_tlsext_host_name(self.ssl_options['server_hostname'].encode('ascii'))
            return connection

    class TwistedConnection(Connection):
        """
        An implementation of :class:`.Connection` that utilizes the
        Twisted event loop.
        """

        _loop = None

        @classmethod
        def initialize_reactor(cls):
            if not cls._loop:
                cls._loop = TwistedLoop()

        @classmethod
        def create_timer(cls, timeout, callback):
            timer = Timer(timeout, callback)
            cls._loop.add_timer(timer)
            return timer

        def __init__(self, *args, **kwargs):
            """
            Initialization method.

            Note that we can't call reactor methods directly here because
            it's not thread-safe, so we schedule the reactor/connection
            stuff to be run from the event loop thread when it gets the
            chance.
            """
            Connection.__init__(self, *args, **kwargs)

            self.is_closed = True
            self.connector = None
            self.transport = None

            reactor.callFromThread(self.add_connection)
            self._loop.maybe_start()

        def _check_pyopenssl(self):
            if self.ssl_context or self.ssl_options:
                if not _HAS_SSL:
                    raise ImportError(
                        str(import_exception) +
                        ', pyOpenSSL must be installed to enable SSL support with the Twisted event loop'
                    )

        def add_connection(self):
            """
            Convenience function to connect and store the resulting
            connector.
            """
            host, port = self.endpoint.resolve()
            if self.ssl_context or self.ssl_options:
                # Can't use optionsForClientTLS here because it *forces* hostname verification.
                # Cool they enforce strong security, but we have to be able to turn it off
                self._check_pyopenssl()

                ssl_connection_creator = _SSLCreator(
                    self.endpoint,
                    self.ssl_context if self.ssl_context else None,
                    self.ssl_options,
                    self._check_hostname,
                    self.connect_timeout,
                )

                endpoint = SSL4ClientEndpoint(
                    reactor,
                    host,
                    port,
                    sslContextFactory=ssl_connection_creator,
                    timeout=self.connect_timeout,
                )
            else:
                endpoint = TCP4ClientEndpoint(
                    reactor,
                    host,
                    port,
                    timeout=self.connect_timeout
                )
            connectProtocol(endpoint, TwistedConnectionProtocol(self))

        def client_connection_made(self, transport):
            """
            Called by twisted protocol when a connection attempt has
            succeeded.
            """
            with self.lock:
                self.is_closed = False
            self.transport = transport
            self._send_options_message()

        def close(self):
            """
            Disconnect and error-out all requests.
            """
            with self.lock:
                if self.is_closed:
                    return
                self.is_closed = True

            log.debug("Closing connection (%s) to %s", id(self), self.endpoint)
            reactor.callFromThread(self.transport.connector.disconnect)
            log.debug("Closed socket to %s", self.endpoint)

            if not self.is_defunct:
                self.error_all_requests(
                    ConnectionShutdown("Connection to %s was closed" % self.endpoint))
                # don't leave in-progress operations hanging
                self.connected_event.set()

        def handle_read(self):
            """
            Process the incoming data buffer.
            """
            self.process_io_buffer()

        def push(self, data):
            """
            This function is called when outgoing data should be queued
            for sending.

            Note that we can't call transport.write() directly because
            it is not thread-safe, so we schedule it to run from within
            the event loop when it gets the chance.
            """
            reactor.callFromThread(self.transport.write, data)