"""
    Slixmpp: The Slick XMPP Library
    Copyright (C) 2012 Nathanael C. Fritz, Lance J.T. Stout
    This file is part of Slixmpp.

    See the file LICENSE for copying permission.
"""

import asyncio
import logging
import collections

from slixmpp.stanza import Message, Presence, Iq, StreamFeatures
from slixmpp.xmlstream import register_stanza_plugin
from slixmpp.xmlstream.handler import Callback, Waiter
from slixmpp.xmlstream.matcher import MatchXPath, MatchMany
from slixmpp.plugins.base import BasePlugin
from slixmpp.plugins.xep_0198 import stanza


log = logging.getLogger(__name__)


MAX_SEQ = 2 ** 32


class XEP_0198(BasePlugin):

    """
    XEP-0198: Stream Management
    """

    name = 'xep_0198'
    description = 'XEP-0198: Stream Management'
    dependencies = set()
    stanza = stanza
    default_config = {
        #: The last ack number received from the server.
        'last_ack': 0,

        #: The number of stanzas to wait between sending ack requests to
        #: the server. Setting this to ``1`` will send an ack request after
        #: every sent stanza. Defaults to ``5``.
        'window': 5,

        #: The stream management ID for the stream. Knowing this value is
        #: required in order to do stream resumption.
        'sm_id': None,

        #: A counter of handled incoming stanzas, mod 2^32.
        'handled': 0,

        #: A counter of unacked outgoing stanzas, mod 2^32.
        'seq': 0,

        #: Control whether or not the ability to resume the stream will be
        #: requested when enabling stream management. Defaults to ``True``.
        'allow_resume': True,

        'order': 10100,
        'resume_order': 9000
    }

    def plugin_init(self):
        """Start the XEP-0198 plugin."""

        # Only enable stream management for non-components,
        # since components do not yet perform feature negotiation.
        if self.xmpp.is_component:
            return

        self.window_counter = self.window

        self.enabled = False
        self.unacked_queue = collections.deque()

        register_stanza_plugin(StreamFeatures, stanza.StreamManagement)
        self.xmpp.register_stanza(stanza.Enable)
        self.xmpp.register_stanza(stanza.Enabled)
        self.xmpp.register_stanza(stanza.Resume)
        self.xmpp.register_stanza(stanza.Resumed)
        self.xmpp.register_stanza(stanza.Ack)
        self.xmpp.register_stanza(stanza.RequestAck)

        # Only end the session when a </stream> element is sent,
        # not just because the connection has died.
        self.xmpp.end_session_on_disconnect = False

        # Register the feature twice because it may be ordered two
        # different ways: enabling after binding and resumption
        # before binding.
        self.xmpp.register_feature('sm',
                self._handle_sm_feature,
                restart=True,
                order=self.order)
        self.xmpp.register_feature('sm',
                self._handle_sm_feature,
                restart=True,
                order=self.resume_order)

        self.xmpp.register_handler(
                Callback('Stream Management Enabled',
                    MatchXPath(stanza.Enabled.tag_name()),
                    self._handle_enabled,
                    instream=True))

        self.xmpp.register_handler(
                Callback('Stream Management Resumed',
                    MatchXPath(stanza.Resumed.tag_name()),
                    self._handle_resumed,
                    instream=True))

        self.xmpp.register_handler(
                Callback('Stream Management Failed',
                    MatchXPath(stanza.Failed.tag_name()),
                    self._handle_failed,
                    instream=True))

        self.xmpp.register_handler(
                Callback('Stream Management Ack',
                    MatchXPath(stanza.Ack.tag_name()),
                    self._handle_ack,
                    instream=True))

        self.xmpp.register_handler(
                Callback('Stream Management Request Ack',
                    MatchXPath(stanza.RequestAck.tag_name()),
                    self._handle_request_ack,
                    instream=True))

        self.xmpp.add_filter('in', self._handle_incoming)
        self.xmpp.add_filter('out_sync', self._handle_outgoing)

        self.xmpp.add_event_handler('session_end', self.session_end)

    def plugin_end(self):
        if self.xmpp.is_component:
            return

        self.xmpp.unregister_feature('sm', self.order)
        self.xmpp.unregister_feature('sm', self.resume_order)
        self.xmpp.del_event_handler('session_end', self.session_end)
        self.xmpp.del_filter('in', self._handle_incoming)
        self.xmpp.del_filter('out_sync', self._handle_outgoing)
        self.xmpp.remove_handler('Stream Management Enabled')
        self.xmpp.remove_handler('Stream Management Resumed')
        self.xmpp.remove_handler('Stream Management Failed')
        self.xmpp.remove_handler('Stream Management Ack')
        self.xmpp.remove_handler('Stream Management Request Ack')
        self.xmpp.remove_stanza(stanza.Enable)
        self.xmpp.remove_stanza(stanza.Enabled)
        self.xmpp.remove_stanza(stanza.Resume)
        self.xmpp.remove_stanza(stanza.Resumed)
        self.xmpp.remove_stanza(stanza.Ack)
        self.xmpp.remove_stanza(stanza.RequestAck)

    def session_end(self, event):
        """Reset stream management state."""
        self.enabled = False
        self.unacked_queue.clear()
        self.sm_id = None
        self.handled = 0
        self.seq = 0
        self.last_ack = 0

    def send_ack(self):
        """Send the current ack count to the server."""
        ack = stanza.Ack(self.xmpp)
        ack['h'] = self.handled
        self.xmpp.send_raw(str(ack))

    def request_ack(self, e=None):
        """Request an ack from the server."""
        req = stanza.RequestAck(self.xmpp)
        self.xmpp.send_raw(str(req))

    async def _handle_sm_feature(self, features):
        """
        Enable or resume stream management.

        If no SM-ID is stored, and resource binding has taken place,
        stream management will be enabled.

        If an SM-ID is known, and the server allows resumption, the
        previous stream will be resumed.
        """
        if 'stream_management' in self.xmpp.features:
            # We've already negotiated stream management,
            # so no need to do it again.
            return False
        if not self.sm_id:
            if 'bind' in self.xmpp.features:
                enable = stanza.Enable(self.xmpp)
                enable['resume'] = self.allow_resume
                enable.send()
                self.enabled = True
                self.handled = 0
                self.unacked_queue.clear()

                waiter = Waiter('enabled_or_failed',
                        MatchMany([
                            MatchXPath(stanza.Enabled.tag_name()),
                            MatchXPath(stanza.Failed.tag_name())]))
                self.xmpp.register_handler(waiter)
                result = await waiter.wait()
        elif self.sm_id and self.allow_resume and 'bind' not in self.xmpp.features:
            self.enabled = True
            resume = stanza.Resume(self.xmpp)
            resume['h'] = self.handled
            resume['previd'] = self.sm_id
            resume.send()

            # Wait for a response before allowing stream feature processing
            # to continue. The actual result processing will be done in the
            # _handle_resumed() or _handle_failed() methods.
            waiter = Waiter('resumed_or_failed',
                    MatchMany([
                        MatchXPath(stanza.Resumed.tag_name()),
                        MatchXPath(stanza.Failed.tag_name())]))
            self.xmpp.register_handler(waiter)
            result = await waiter.wait()
            if result is not None and result.name == 'resumed':
                return True
        return False

    def _handle_enabled(self, stanza):
        """Save the SM-ID, if provided.

        Raises an :term:`sm_enabled` event.
        """
        self.xmpp.features.add('stream_management')
        if stanza['id']:
            self.sm_id = stanza['id']
        self.xmpp.event('sm_enabled', stanza)

    def _handle_resumed(self, stanza):
        """Finish resuming a stream by resending unacked stanzas.

        Raises a :term:`session_resumed` event.
        """
        self.xmpp.features.add('stream_management')
        self._handle_ack(stanza)
        for id, stanza in self.unacked_queue:
            self.xmpp.send(stanza, use_filters=False)
        self.xmpp.event('session_resumed', stanza)

    def _handle_failed(self, stanza):
        """
        Disable and reset any features used since stream management was
        requested (tracked stanzas may have been sent during the interval
        between the enable request and the enabled response).

        Raises an :term:`sm_failed` event.
        """
        self.enabled = False
        self.unacked_queue.clear()
        self.xmpp.event('sm_failed', stanza)

    def _handle_ack(self, ack):
        """Process a server ack by freeing acked stanzas from the queue.

        Raises a :term:`stanza_acked` event for each acked stanza.
        """
        if ack['h'] == self.last_ack:
            return

        num_acked = (ack['h'] - self.last_ack) % MAX_SEQ
        num_unacked = len(self.unacked_queue)
        log.debug("Ack: %s, Last Ack: %s, " + \
                  "Unacked: %s, Num Acked: %s, " + \
                  "Remaining: %s",
            ack['h'],
            self.last_ack,
            num_unacked,
            num_acked,
            num_unacked - num_acked)
        if num_acked > len(self.unacked_queue) or num_acked < 0:
            log.error('Inconsistent sequence numbers from the server,'
                      ' ignoring and replacing ours with them.')
            num_acked = len(self.unacked_queue)
        for x in range(num_acked):
            seq, stanza = self.unacked_queue.popleft()
            self.xmpp.event('stanza_acked', stanza)
        self.last_ack = ack['h']

    def _handle_request_ack(self, req):
        """Handle an ack request by sending an ack."""
        self.send_ack()

    def _handle_incoming(self, stanza):
        """Increment the handled counter for each inbound stanza."""
        if not self.enabled:
            return stanza

        if isinstance(stanza, (Message, Presence, Iq)):
            # Sequence numbers are mod 2^32
            self.handled = (self.handled + 1) % MAX_SEQ
        return stanza

    def _handle_outgoing(self, stanza):
        """Store outgoing stanzas in a queue to be acked."""
        if not self.enabled:
            return stanza

        if isinstance(stanza, (Message, Presence, Iq)):
            seq = None
            # Sequence numbers are mod 2^32
            self.seq = (self.seq + 1) % MAX_SEQ
            seq = self.seq
            self.unacked_queue.append((seq, stanza))
            self.window_counter -= 1
            if self.window_counter == 0:
                self.window_counter = self.window
                self.request_ack()
        return stanza
