.. _using_asyncio:

=============
Using asyncio
=============

Block on IQ sending
~~~~~~~~~~~~~~~~~~~

:meth:`.Iq.send` now returns a :class:`~.Future` so you can easily block with:

.. code-block:: python

    result = await iq.send()

.. warning::

    If the reply is an IQ with an ``error`` type, this will raise an
    :class:`.IqError`, and if it timeouts, it will raise an
    :class:`.IqTimeout`. Don't forget to catch it.

You can still use callbacks instead.

XEP plugin integration
~~~~~~~~~~~~~~~~~~~~~~

The same changes from the SleekXMPP API apply, so you can do:

.. code-block:: python

    iq_info = await self.xmpp.plugin['xep_0030'].get_info(jid)


Callbacks, Event Handlers, and Stream Handlers
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

IQ callbacks and :term:`Event Handlers <event handler>` can be coroutine
functions; in this case, they will be scheduled in the event loop using
:meth:`.asyncio.ensure_future` and not ran immediately.

A :class:`.CoroutineCallback` class has been added as well for
:term:`Stream Handlers <stream handler>`, which will use
:meth:`.asyncio.async` to schedule the callback.

Running the event loop
~~~~~~~~~~~~~~~~~~~~~~

You can handle the event loop in any way you like, either forever, until an
event, only for a specific duration, in conjunction with another asyncio user,
anything goes.  But remember slixmpp will only process events and send messages
when its event loop is running.


Using connect()
~~~~~~~~~~~~~~~

:meth:`.XMLStream.connect` schedules a lot of things in the background, but that
only holds true if the event loop is running!

That is why in all examples we usually call connect() right before calling
a `loop.run_…` function.

Using a different event loop
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Immediately upon XMPP object creation (`ClientXMPP` / `ComponentXMPP`) you
should sets its `loop` attribute to whatever you want, and ideally this
should work. This path is less tested, so it may break, if that is the case
please report a bug.

Any access to the `loop` attribute if not user-initialized will set it
to the default asyncio event loop by default.

.. warning::

    If the loop attribute is modified at runtime, the application will probably
    end up in an hybrid state and asyncio may complain loudly that things bound
    to an event loop are being ran in another. Try to avoid that situation.


Examples
~~~~~~~~

Blocking until the session is established
-----------------------------------------

This code blocks until the XMPP session is fully established, which
can be useful to make sure external events aren’t triggering XMPP
callbacks while everything is not ready.

.. code-block:: python

    import asyncio, slixmpp

    client = slixmpp.ClientXMPP('jid@example', 'password')
    client.connected_event = asyncio.Event()
    callback = lambda _: client.connected_event.set()
    client.add_event_handler('session_start', callback)
    client.connect()
    loop = asyncio.get_event_loop()
    loop.run_until_complete(event.wait())
    # do some other stuff before running the event loop, e.g.
    # loop.run_until_complete(httpserver.init())
    asyncio.get_event_loop().run_forever()


Use with other asyncio-based libraries
--------------------------------------

This code interfaces with aiohttp to retrieve two pages asynchronously
when the session is established, and then send the HTML content inside
a simple <message>.

.. code-block:: python

    import aiohttp, slixmpp

    async def get_pythonorg(event):
        async with aiohttp.ClientSession() as session:
            async with session.get('http://www.python.org') as resp:
                text = await req.text()
        client.send_message(mto='jid2@example', mbody=text)

    async def get_asyncioorg(event):
        async with aiohttp.ClientSession() as session:
            async with session.get('http://www.asyncio.org') as resp:
                text = await req.text()
        client.send_message(mto='jid3@example', mbody=text)

    client = slixmpp.ClientXMPP('jid@example', 'password')
    client.add_event_handler('session_start', get_pythonorg)
    client.add_event_handler('session_start', get_asyncioorg)
    client.connect()
    client.loop.run_until_complete(client.disconnected)


Blocking Iq
-----------

This client checks (via XEP-0092) the software used by every entity it
receives a message from. After this, it sends a message to a specific
JID indicating its findings.

.. code-block:: python

    import asyncio, slixmpp

    class ExampleClient(slixmpp.ClientXMPP):
        def __init__(self, *args, **kwargs):
            slixmpp.ClientXMPP.__init__(self, *args, **kwargs)
            self.register_plugin('xep_0092')
            self.add_event_handler('message', self.on_message)

        async def on_message(self, event):
            # You should probably handle IqError and IqTimeout exceptions here
            # but this is an example.
            version = await self['xep_0092'].get_version(message['from'])
            text = "%s sent me a message, he runs %s" % (message['from'],
                                                         version['software_version']['name'])
            self.send_message(mto='master@example.tld', mbody=text)

    client = ExampleClient('jid@example', 'password')
    client.connect()
    asyncio.get_event_loop().run_forever()
